Semiconductor laser element

The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device including an active layer.

Conventionally, a semiconductor laser device including a semiconductor layer having a convex portion (ridge portion) and a flat portion other than the convex portion on the active layer is known.

FIG. 27 is a perspective view showing the structure of a conventional semiconductor laser device. 28 and 29 are side views and top views for explaining the vertical and horizontal spread angles of the laser beam of the conventional semiconductor laser device shown in FIG. 27, respectively. First, referring to FIG. 27, in the conventional semiconductor laser device, an n-side clad layer 102 made of an n-type semiconductor is formed on the n-type semiconductor substrate 101. An active layer 103 is formed on the n-side clad layer 102. On the active layer 103, a p-side clad layer 104 made of a p-type semiconductor having a convex portion and a flat portion other than the convex portion is formed. A contact layer 105 made of a p-type semiconductor is formed on the convex portion of the p-side clad layer 104. The contact layer 105 and the convex portion of the p-side clad layer 104 form a striped (elongated) ridge portion 106 extending in the resonator direction. A p-side ohmic electrode 107 is formed on the contact layer 105 constituting the ridge portion 106. Further, a part of the n-type semiconductor substrate 101 is exposed by removing a predetermined region from the upper surface of the flat portion of the p-side clad layer 104 to a depth in the middle of the n-type semiconductor substrate 101. An n-side ohmic electrode 108 is formed in a predetermined region on the exposed surface of the n-type semiconductor substrate 101. Further, a current block layer 109 made of an insulating film is formed on the surfaces other than the p-side ohmic electrode 107 and the n-side ohmic electrode 108.

In the conventional semiconductor laser device shown in FIG. 27, the light generated by the active layer 103 is reflected by the resonator end faces 100a and 100b to oscillate the laser. The spot shape (light intensity distribution) of the laser beam emitted from the resonator end surface 100a on the light emitting side is controlled by light confinement from the vertical direction and the horizontal direction. Specifically, light confinement in the vertical direction is performed by the p-side clad layer 104 and the n-side clad layer 102 located above and below the active layer 103, respectively. Further, the light confinement in the horizontal direction is performed by the portion where the convex portion and the flat portion of the p-side clad layer 104 intersect (the lower end portion of the convex portion). In the conventional semiconductor laser device shown in FIG. 27, as shown in FIG. 28, the vertical spread angle θ1 of the emitted laser light is about 18 °. Further, as shown in FIG. 29, the horizontal spread angle θ2 of the emitted laser light is about 6 °. That is, in the conventional semiconductor laser device shown in FIG. 27, θ1 (vertical spread angle) / θ2 (horizontal spread angle) = about 3.

In the conventional semiconductor laser device shown in FIG. 27, as described above, the horizontal spread angle θ2 (about 6 °) is smaller than the vertical spread angle θ1 (about 18 °) of the laser beam, so that the laser It was difficult to make the shape of the light close to a perfect circle (θ1 / θ2 = 1). Therefore, there is a disadvantage that it is difficult to obtain a semiconductor laser element having a good light intensity distribution close to a perfect circle shape.

Therefore, conventionally, by strengthening the light confinement in the horizontal direction only in the region near the end face of the optical cavity on the light emitting side, the shape (light intensity distribution) of the light emitting spot of the laser light is suppressed from spreading in the horizontal direction. Has proposed a method for increasing the horizontal spread angle θ2 of the laser beam (see, for example, Patent Document 1). The smaller the horizontal spread of the shape of the light emitting spot (light intensity distribution), the larger the horizontal spread angle θ2.

In Patent Document 1, a semiconductor laser in which an n-side clad layer, an active layer, and a p-side clad layer are sequentially formed on a substrate, and the p-side clad layer has a convex portion and a flat portion other than the convex portion. In the device, only the region near the end face of the resonator on the light emitting side is etched from the upper surface of the flat portion of the p-side clad layer to the depth in the middle of the active layer and the n-side clad layer. In Patent Document 1, since the width of the active layer is reduced by etching the active layer, it is possible to strengthen the light confinement in the horizontal direction.<patcit num="1"><text>Japanese Patent Application Laid-Open No. 2002-374035</text></patcit>

<p> However, in Patent Document 1, since the active layer is etched in the region near the end face of the resonator on the light emitting side, there is a disadvantage that the etching damage applied to the active layer becomes large. As a result, the crystal defects of the active layer generated due to the etching damage increase, so that there is a disadvantage that the light absorption by the crystal defect portion of the active layer increases. As a result, there is a problem that the luminous efficiency is lowered. Further, there is a problem that crystal defects grow due to the flow of an electric current through the crystal defect portion of the active layer.</p><p> Further, as another method of strengthening the light confinement in the horizontal direction, there is a method of reducing the width of the convex portion of the p-side clad layer. In this case, since the distance between the edge portions having the light confinement function in the horizontal direction becomes small, the width of the light confinement in the horizontal direction can be reduced.</p><p> However, in the method of reducing the width of the convex portion of the p-side clad layer, the contact area with the electrode layer formed on the convex portion of the p-side clad layer becomes small, which causes a disadvantage that the contact resistance increases. As a result, the operating voltage of the element becomes high, so that there is a problem that the power consumption of the element increases.</p><p> The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to have a high luminous efficiency and a shape of a laser beam that is closer to a perfect circle shape than before. It is to provide the semiconductor laser element which can obtain.</p>

Means for Solving Problems and Effects of Invention

In order to achieve the above object, the semiconductor laser device according to one aspect of the present invention has an active layer formed on the first semiconductor layer and a convex portion and a flat portion other than the convex portion formed on the active layer. It is provided with a second semiconductor layer having and. The flat portion of the second semiconductor layer is located at least in the first flat portion located in the first region near the end face of the resonator on the light emitting side and in the second region including the central region of the element other than the first region. The thickness of the first flat portion of the second semiconductor layer including the second flat portion is smaller than the thickness of the second flat portion of the second semiconductor layer.

In the semiconductor laser device according to this one aspect, as described above, the flat portion other than the convex portion of the second semiconductor layer formed on the active layer is located at least in the first region near the end face of the resonator on the light emitting side. The first flat portion to be formed and the second flat portion located in the second region including the central region of the element other than the first region are included, and the thickness of the first flat portion is set to be the thickness of the second flat portion. By making it smaller than the thickness, the lower end of the convex portion of the second semiconductor layer located in the first region near the end face of the resonator on the light emitting side is positioned in the second region including the central region of the device. Since it is possible to bring the active layer closer to the lower end of the convex portion of the layer, the lower end of the convex portion of the first region formed so as to be closer to the active layer provides horizontal light confinement in the first region. Can be strong. As a result, the horizontal spread of the laser beam emission spot can be reduced, so that the horizontal spread angle of the laser beam can be increased. As a result, the shape of the laser beam can be made close to a perfect circle (vertical spread angle / horizontal spread angle = 1). In this case, when the convex portion (ridge portion) of the second semiconductor layer is formed by etching, the thickness of the second flat portion located in the second region of the second semiconductor layer is the first flat portion located in the first region. Since the etching is performed so as to be larger than the thickness of the above, the etching damage applied to the second flat portion of the second region can be made smaller than the etching damage applied to the first flat portion of the first region. Thereby, in the second region, the amount of crystal defects in the active layer under the second flat portion generated due to etching damage can be reduced. Further, even in the active layer located below the first flat portion of the first region, the active layer is not etched, so that it is caused by etching damage as compared with the case where the ridge portion is formed by etching the portion including the active layer. Therefore, the amount of crystal defects generated in the active layer can be reduced. As a result, it is possible to suppress an increase in the leakage current that does not contribute to light emission flowing through the crystal defect portion of the active layer. In addition, the fewer crystal defects in the active layer, the more current flows. It is possible to suppress the growth of crystal defects caused by this. As a result, it is possible to obtain a semiconductor laser element having a long life and high luminous efficiency. As described above, in the semiconductor laser device according to one aspect, it is possible to obtain a semiconductor laser device having a long life, high luminous efficiency, and capable of obtaining a laser beam shape close to a perfect circle shape.

The semiconductor laser device according to the above one aspect is preferably configured such that the current density of the current flowing through the first region is smaller than the current density of the current flowing through the second region. With this configuration, the current injected into the active layer located in the first region near the end face of the resonator on the light emitting side is larger than the current flowing in the active layer located in the second region including the central region of the device. Since it can be reduced, the thickness of the first flat portion of the second semiconductor layer in the first region is made smaller than the thickness of the second flat portion of the second semiconductor layer in the second region. Even if the number of crystal defects in the active layer located in the region is larger than that in the active layer located in the second region, the current flowing through the crystal defect portion of the active layer located in the first region can be reduced. it can. As a result, it is possible to suppress an increase in crystal defects due to a large amount of current flowing through the crystal defect portion of the active layer, so that the life of the device can be extended.

In this case, preferably, the first electrode layer formed on the second semiconductor layer and having a sheet resistance value of 1 Ω / or more and the end portion formed on the first electrode layer on the light emitting side emit light. A second electrode layer arranged at a predetermined distance from the end face of the resonator on the side is further provided. With this configuration, the current can be injected from the second electrode layer only in a region separated by a predetermined distance from the resonator end face on the light emitting side of the first electrode layer. When the end of the first electrode layer on the light emitting side reaches the end face of the resonator, the sheet resistance value of the first electrode layer is set to a large sheet resistance value of 1Ω / or more to obtain a second sheet resistance value. When a current is injected from the electrode layer, it becomes difficult for the current to flow in the resonator direction (horizontal direction) in the first electrode layer, so that the current of the current flowing in the first region near the end face of the resonator on the light emitting side can be easily obtained. The density can be made smaller than the current density of the current flowing through the second region including the central region of the element other than the first region.

In this case, preferably, the end portion of the second electrode layer on the light emitting side is arranged on the second region side of the boundary between the first region and the second region. With this configuration, as described above, in the configuration in which the current does not easily flow in the resonator direction in the first electrode layer, a predetermined value is formed between the end of the second electrode layer on the light emitting side and the first region. Since the interval is provided, it becomes more difficult for the current to be injected into the first region from the second electrode layer through the first electrode layer. As a result, the current density of the current flowing through the first region near the resonator end face on the light emitting side is made smaller than the current density of the current flowing through the second region including the central region of the device other than the first region. can do.

In the semiconductor laser device according to the above one aspect, preferably, the upper surface of the first flat portion and the upper surface of the second flat portion are connected between the first flat portion and the second flat portion of the second semiconductor layer. As described above, an inclined portion is provided. With this configuration, the boundary surface between the first flat portion and the second flat portion is inclined, so that the first flat portion and the second flat portion having different thicknesses are connected by a vertical boundary surface. Compared to the case, the light is less likely to be reflected in the direction of the end face of the resonator on the boundary surface opposite to the light emitting side. As a result, it is possible to suppress the generation of an unnecessary laser oscillation mode between the boundary surface between the first flat portion and the second flat portion and the resonator end surface on the side opposite to the light emitting side. As a result, the laser oscillation mode having high luminous efficiency (laser oscillation mode between the resonator end face on the light emitting side and the resonator end face on the opposite side to the light emitting side) can be maintained up to the high output region. Therefore, the luminous efficiency can be further improved. Further, by providing an inclined portion between the first flat portion and the second flat portion of the second semiconductor layer so as to connect the upper surface of the first flat portion and the upper surface of the second flat portion, the thickness can be increased. The lower end (edge) of the interface between the first flat and the second flat is smoother than when different first and second flats are connected by a vertical interface. Therefore, the light confinement by the edge portion can be weakened. As a result, the light loss at the edge portion of the boundary surface between the first flat portion and the second flat portion can be suppressed, and thus the luminous efficiency can be further improved.

In the semiconductor laser device according to the above one aspect, preferably, the flat portion of the second semiconductor layer is located in the third region near the end face of the resonator on the side opposite to the light emitting side, and is based on the thickness of the second flat portion. Also includes a third flat portion with a small thickness. With this configuration, even if the end face of the resonator opposite to the light emitting side is used as the light emitting surface, the shape of the laser beam is a perfect circle (vertical spread angle / horizontal spread angle = 1). Can be approached to. As a result, the shape of the laser beam can be made close to a perfect circle regardless of which of the two resonator end faces is used as the light emitting surface. As a result, it is possible to manufacture a semiconductor laser device capable of obtaining a laser beam shape close to a perfect circle shape regardless of which resonator end face is set as the light emitting surface when assembling the device.

In the semiconductor laser device according to the above one aspect, the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction is preferably 3 μm or more and 50 μm or less. With this configuration, the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction is set to 3 μm or more, so that the first region near the end face of the resonator on the light emitting side can be obtained. It is possible to prevent insufficient horizontal light confinement in the first region due to the length of the first flat portion located in the resonator direction becoming too small. Further, by setting the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction to 3 μm or more, the first region is used when the element is separated into each chip by the cleavage method. It is possible to prevent the element from being separated in the second region including the central region of the element due to the length of the first flat portion located in the element in the resonator direction becoming too small. Further, by setting the length of the first flat portion of the second semiconductor layer located in the first region in the resonator direction to 50 μm or less, the first flat portion located in the first flat region where the etching damage is larger than that of the second region. It is possible to suppress an increase in the number of crystal defects introduced into the active layer due to the length of the portion in the resonator direction becoming too large.

In the semiconductor laser device according to the above one aspect, the thickness of the second flat portion of the second semiconductor layer located in the second region is preferably 100 nm or more and 250 nm or less. With this configuration, the thickness of the second flat portion of the second semiconductor layer located in the second region is set to 100 nm or more, so that the thickness of the second flat portion located in the second region including the central region of the device is set to 100 nm or more. Since it is possible to suppress the increase in etching damage applied to the second flat portion due to making the second flat portion too small, it is possible to reduce the amount of crystal defects generated in the active layer located under the second flat portion. Can be done. As a result, the increase in light absorption due to the crystal defect portion of the active layer can be further suppressed, so that the luminous efficiency can be further improved. Moreover, since the growth of crystal defects can be suppressed, the device life can be further improved. Further, by reducing the thickness of the second flat portion of the second semiconductor layer located in the second region to 250 nm or less, the thickness of the second flat portion located in the second region is made too large. Since it is possible to suppress an increase in the threshold current, it is possible to suppress an increase in power consumption.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view showing the structure of a nitride semiconductor laser device according to the first embodiment of the present invention. 2 and 3 are cross-sectional views taken along lines 100-100 and 200-200 of FIG. 1, respectively. First, the structure of the nitride-based semiconductor laser device according to the first embodiment will be described with reference to FIGS. 1 to 3. The width W of the nitride semiconductor laser device according to the first embodiment is about 300 μm, and the length L of the resonator is about 600 μm.

In the nitride-based semiconductor laser device according to the first embodiment, as shown in FIG. 1, the n-side composed of n-type AlGaN (Al composition ratio: 7%) having a thickness of about 1.5 μm on the n-type GaN substrate 1. The clad layer 2 is formed. The n-side clad layer 2 is an example of the "first semiconductor layer" of the present invention. An active layer (light emitting layer) 3 is formed on the n-side clad layer 2. This active layer 3 is composed of three well layers made of undoped InGaN (In composition ratio: 15%) having a thickness of about 3 nm and undoped InGaN (In composition ratio: 2%) having a thickness of about 20 nm. It has a multiple quantum well (MQW) structure in which three barrier layers are alternately laminated. Further, a p-side clad layer 4 is formed on the active layer 3. The p-side clad layer 4 is composed of an optical guide layer (not shown), a cap layer (not shown), and a p-type AlGaN layer (not shown) in this order from the active layer 3 side. The optical guide layer constituting the p-side clad layer 4 is made of undoped InGaN (In composition ratio: 1%) having a thickness of about 75 nm, and the cap layer is an undoped AlGaN (Al composition) having a thickness of about 20 nm. Ratio: 20%). In addition, the p-type AlGaN layer is doped with Mg and has an Al composition ratio of 7%. The p-side clad layer 4 has a width of about 1.5 μm and has a striped (elongated) convex portion extending in the resonator direction. The p-side clad layer 4 is an example of the "second semiconductor layer" of the present invention.

Here, in the first embodiment, the flat portions 4a and 4b other than the convex portion of the p-side clad layer 4 include the region A1 near the resonator end face 10a on the light emitting side and the central region of the element other than the region A1. It has a different thickness from the region B1. Specifically, in region A1, as shown in FIG. 2, the thickness tA1 of the flat portion 4a from the upper surface of the active layer 3 to the p-side clad layer 4 is about 100 nm, and the upper surface of the flat portion 4a of the convex portion. The height from is about 400 nm. Further, in the region B1, as shown in FIG. 3, the thickness tB1 of the flat portion 4b of the p-side clad layer 4 is about 150 nm, and the height from the upper surface of the flat portion 4b of the convex portion is about 350 nm. .. That is, the thickness tA1 of the flat portion 4a of the region A1 is smaller than the thickness tB1 of the flat portion 4b of the region B1. The regions A1 and B1 are examples of the "first region" and the "second region" of the present invention, respectively, and the flat portions 4a and 4b are the "first flat portion" and the "first flat portion" of the present invention, respectively. This is an example of "2 flat part". The length of the region A1 in the resonator direction is about 10 μm, and the length of the region B1 in the resonator direction is about 590 μm.

Further, as shown in FIG. 1, a contact layer 5 made of undoped InGaN (In composition ratio: 7%) having a thickness of about 3 nm is formed on the convex portion of the p-side clad layer 4. The contact layer 5 is an example of the "second semiconductor layer" of the present invention. The contact layer 5 and the convex portion of the p-side clad layer 4 form a striped (elongated) ridge portion 6 having a width of about 1.5 μm and extending in the resonator direction. Further, SiO having a thickness of about 200 nm is formed on the upper surfaces of the flat portions 4a and 4b of the p-side clad layer 4 and on the side surfaces of the ridge portion 6.₂A current block layer 7 made of a film is formed. Further, a p-side ohmic electrode 8 is formed on the contact layer 5 constituting the ridge portion 6. The p-side ohmic electrode 8 has a Pt layer (not shown) having a thickness of about 1 nm, a Pd layer (not shown) having a thickness of about 100 nm, and Au having a thickness of about 100 nm, in order from the contact layer 5 side. It is composed of layers (not shown).

Further, an n-side ohmic electrode 9 is formed in a predetermined region on the back surface of the n-type GaN substrate 1. The n-side ohmic electrode 9 has an Al layer having a thickness of about 6 nm (not shown), a Pd layer having a thickness of about 10 nm (not shown), and a thickness of about 300 nm in order from the n-type GaN substrate 1 side. It is composed of an Au layer (not shown).

Then, in the nitride-based semiconductor laser device according to the first embodiment, the light generated in the active layer 3 is reflected by the resonator end faces 10a and 10b to oscillate the laser.

Figure 4 shows the horizontal direction of the laser beam when the length of the region near the resonator end face on the light emitting side in the resonator direction is changed in 5 steps (0 μm, about 3 μm, about 10 μm, about 50 μm, and about 200 μm). It is a graph which showed the spread angle of. Next, with reference to FIG. 4, in the configuration of the nitride-based semiconductor laser device of the first embodiment, the length of the region A1 (the region near the end face of the resonator on the light emitting side) in the resonator direction is changed. The result of measuring the horizontal spread angle θ2 of the laser beam will be described.

As shown in FIG. 4, it was found that when the length of the region A1 in the resonator direction is about 3 μm or more, the horizontal spread angle θ2 of the laser beam becomes as large as about 8 ° or more. Specifically, when the lengths of the region A1 in the resonator direction are about 3 μm, about 10 μm, about 50 μm, and about 200 μm, the horizontal spread angles θ2 of the laser beam are about 8 ° and about 10 °, respectively. It was about 11.3 ° and about 11.5 °. On the other hand, it was found that when the length of the region A1 in the resonator direction is 0 μm, the horizontal spread angle θ2 of the laser beam becomes as small as about 6 °. When the length of the region A1 in the resonator direction is 0 μm, the horizontal spread angle θ2 of the laser beam is small because the length of the flat portion 4a located in the region A1 in the resonator direction becomes 0. It is considered that this is because the horizontal light confinement in the region A1 became insufficient. Therefore, in order to increase the horizontal spread angle θ2 of the laser beam to about 8 ° or more, it is considered preferable to set the length of the region A1 in the resonator direction to about 3 μm or more. If the length of the flat portion 4a located in the region A1 in the resonator direction is small, the element is separated from the region B1 including the central region of the element when the element is separated into each chip by the cleavage method. In this respect as well, it is considered preferable to set the length of the region A1 in the resonator direction to about 3 μm or more.

It was also found that the horizontal spread angle θ2 of the laser beam hardly changed between the case where the length of the region A1 in the resonator direction was about 50 μm and the case where the length was about 200 μm. Here, if the length of the region A1 in the resonator direction is made too large, the length of the flat portion 4a of the region A1 in the resonator direction, which has a thickness smaller than that of the flat portion 4b of the region B1, becomes large. In this case, when the convex portion of the p-side clad layer 4 is formed by etching, the amount of etching in the p-side clad layer 4 becomes large. As a result, the etching damage applied to the p-side clad layer 4 becomes large, so that the amount of crystal defects generated in the active layer 3 located under the p-side clad layer 4 increases. Therefore, it is considered preferable to set the length of the region A1 in the resonator direction to about 50 μm or less. From these results, it is preferable that the length of the region A1 in the resonator direction is set to about 3 μm or more and about 50 μm or less.

Here, in the first embodiment, since the length of the region A1 in the resonator direction is set to about 10 μm, the laser beam is horizontal while suppressing the etching damage applied to the p-side clad layer 4 from becoming large. It is considered that the spread angle θ2 in the direction can be increased.

Next, in the configuration of the nitride-based semiconductor laser device of the first embodiment, the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is set in five stages (about 70 nm, about 100 nm, about 150 nm, about 250 nm). And the results of measuring the luminous efficiency and threshold current by changing to about 300 nm) are shown in Table 1 below.

<tables num="1"><img file="JP2005294322A_D0001.tif" /></tables> With reference to Table 1 above, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is about 100 nm or more and about 250 nm or less, the luminous efficiency is as high as about 1.3 W / A or more and It was found that the threshold current was as low as about 53mA or less. Specifically, the luminous efficiencies when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is about 100 nm, about 150 nm, and about 250 nm are about 1.3 W / A and about 1.5 W /, respectively. It was A and about 1.4 W / A, and the threshold currents were about 32 mA, about 30 mA and about 53 mA, respectively.

On the other hand, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is about 70 nm, the threshold current is as low as about 35 mA, while the luminous efficiency is as low as about 0.6 W / A. It has been found. It is considered that this is because the etching damage applied to the p-side clad layer 4 is increased due to the thickness tB1 of the flat portion 4b of the p-side clad layer 4 located in the region B1 being made too small. As a result, the amount of crystal defects generated in the active layer 3 located under the p-side clad layer 4 increases, and the light absorption by the crystal defect portion of the active layer 3 increases, so that the luminous efficiency is considered to have decreased. Be done. Further, when the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is about 300 nm, the luminous efficiency is as high as about 1.3 W / A, while the threshold current is as high as about 105 mA. There was found.

From these results, if the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is set to about 100 nm or more and about 250 nm or less, the luminous efficiency can be increased and the threshold current can be increased. It is thought that it can be lowered.

Here, in the first embodiment, since the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is set to about 150 nm, the luminous efficiency can be increased and the threshold value can be increased. It is considered that the current can be lowered.

In the first embodiment, as described above, the thickness tA1 (about 100 nm) of the flat portion 4a located in the region A1 near the end face 10a of the optical cavity on the light emitting side is set to the region B1 including the central region of the element other than the region A1. By making the thickness of the flat portion 4b located at the position smaller than tB1 (about 150 nm), the lower end of the convex portion of the p-side clad layer 4 located in the region A1 near the resonator end face 10a on the light emitting side can be formed by the element. Since the active layer 3 can be closer to the active layer 3 than the lower end of the convex portion of the p-side clad layer 4 located in the region B1 including the central region, the convex portion of the region A1 formed so as to be closer to the active layer 3 The lower end can enhance the horizontal light confinement in region A1. As a result, the horizontal spread of the laser beam emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle (vertical spread angle θ1 / horizontal spread angle θ2 = 1). In this case, when the convex portion (ridge portion 6) of the p-side clad layer 4 is formed by etching, the thickness tB1 (about 150 nm) of the flat portion 4b located in the region B1 of the p-side clad layer 4 is located in the region A1. Since etching is performed so as to be larger than the thickness tA1 (about 100 nm) of the flat portion 4a to be formed, the etching damage applied to the flat portion 4b of the region B1 can be made smaller than the etching damage applied to the flat portion 4a of the region A1. .. Thereby, in the region B1, the amount of crystal defects in the active layer 3 under the flat portion 4b generated due to the etching damage can be reduced. Further, even in the active layer 3 located below the flat portion 4a of the region A1, the active layer 3 is not etched, so that the etching is performed as compared with the case where the ridge portion 6 is formed by etching the portion including the active layer 3. The amount of crystal defects generated in the active layer 3 due to damage can be reduced. As a result, it is possible to suppress an increase in light absorption due to the crystal defect portion of the active layer 3, so that a nitride-based semiconductor laser device having high luminous efficiency can be obtained. Moreover, since the growth of crystal defects can be suppressed, a highly reliable and long-life device can be obtained. As described above, in the first embodiment, it is possible to obtain a nitride-based semiconductor laser device having high luminous efficiency and capable of obtaining a laser beam shape close to a perfect circle shape.

Further, in the first embodiment, the length of the flat portion 4a located in the region A1 near the resonator end surface 10a on the light emitting side in the resonator direction is set to about 10 μm, whereby the flat portion located in the region A1 is set. It is possible to suppress insufficient horizontal light confinement in the region A1 due to the length of 4a in the resonator direction becoming too small. Further, when the element is separated into each chip by the cleavage method, the length of the flat portion 4a located in the region A1 in the resonator direction becomes too small, so that the element includes the central region of the element. It is possible to suppress device manufacturing defects separated in region B1. In addition, it suppresses the increase of crystal defects introduced into the active layer 3 due to the length of the flat portion 4a located in the region A1 where the etching damage is larger than the region B1 in the resonator direction becoming too large. can do.

Further, in the first embodiment, the thickness tB1 of the flat portion 4b located in the region B1 of the p-side clad layer 4 is set to about 150 nm, so that the thickness tB1 of the flat portion 4b located in the region B1 is made too small. As a result, it is possible to suppress the increase in etching damage applied to the flat portion 4b, so that the amount of crystal defects generated in the active layer 3 located below the flat portion 4b can be reduced. As a result, the increase in light absorption due to the crystal defect portion of the active layer 3 can be further reduced, so that the luminous efficiency can be further improved. Further, since it is possible to suppress an increase in the threshold current due to the thickness tB1 of the flat portion 4b located in the region B1 being made too large, it is possible to suppress an increase in power consumption. it can.

5 to 11 are perspective views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment shown in FIG. Next, the manufacturing process of the nitride-based semiconductor laser device according to the first embodiment will be described with reference to FIGS. 1 and 5 to 11.

First, as shown in Fig. 5, MOCVD (Metal Organic Chemical Vapor) Using the Deposition) method, an n-side clad layer 2 and an active layer 3 made of n-type AlGaN having a thickness of about 1.5 μm are sequentially grown on the n-type GaN substrate 1. When growing the active layer 3, first, three well layers (not shown) made of undoped InGaN having a thickness of about 3 nm and three barriers made of undoped InGaN having a thickness of about 20 nm are formed. By alternately growing layers (not shown), a multilayer film having an MQW structure is formed. As a result, the active layer 3 composed of a multilayer film having an MQW structure composed of three well layers and three barrier layers is formed. Next, on the active layer 3, an optical guide layer made of undoped InGaN having a thickness of about 75 nm (not shown), a cap layer made of undoped AlGaN having a thickness of about 20 nm (not shown), and about 500 nm. A Mg-doped p-type AlGaN layer (not shown) having a thickness of 3 is sequentially grown. As a result, the p-side clad layer 4 composed of the optical guide layer, the cap layer and the p-type AlGaN layer is formed. After that, a contact layer 5 made of undoped InGaN having a thickness of about 3 nm is grown on the p-side clad layer 4.

After that, using a vacuum vapor deposition method or the like, a Pt layer having a thickness of about 1 nm (not shown), a Pd layer having a thickness of about 100 nm (not shown), and a thickness of about 100 nm are formed on the contact layer 5. The Au layer (not shown) is sequentially formed. As a result, the p-side ohmic electrode 8 composed of the Pt layer, the Pd layer and the Au layer is formed.

Next, as shown in FIG. 6, the resist 11 is formed in the formation region of the ridge portion 6 (see FIG. 1) on the p-side ohmic electrode 8.

Next, as shown in Figure 7, CF₄Using the RIE (Reactive Ion Etching) method using a system gas, a predetermined region of the p-side ohmic electrode 8 is removed using the resist 11 as a mask. Then, Cl₂Using the RIE method using a system gas, a predetermined region from the upper surface of the contact layer 5 to the intermediate depth of the p-side clad layer 4 (a depth of about 350 nm from the upper surface of the p-side clad layer 4) using the resist 11 as a mask. To remove. After this, the resist 11 is removed.

Next, as shown in FIG. 8, the resist 12 is formed so as to cover only the p-side clad layer 4, the contact layer 5, and the p-side ohmic electrode 8 located in the region B1 including the central region of the device.

Next, Cl₂Using the RIE method using a system gas, a predetermined region from the upper surface of the flat portion 4b of the p-side clad layer 4 to a depth of about 50 nm is removed using the resist 12 and the p-side ohmic electrode 8 located in the region A1 as a mask. As a result, the flat portions 4a and 4b other than the convex portion of the p-side clad layer 4 include the region A1 near the resonator end surface 10a (see FIG. 1) on the light emitting side and the region including the central region of the element other than the region A1. The thickness is different from that of B1. Specifically, in the region A1, the thickness tA1 of the flat portion 4a of the p-side clad layer 4 is about 100 nm, and the height of the convex portion from the upper surface of the flat portion 4a is about 400 nm. On the other hand, in the region B1, the thickness tB1 of the flat portion 4b of the p-side clad layer 4 is about 150 nm, and the height from the upper surface of the flat portion 4b of the convex portion is about 350 nm. As a result, the ridge portion 6 composed of the convex portion of the p-side clad layer 4 and the contact layer 5 is formed. After that, the resist 12 is removed to bring the resist 12 into the state shown in FIG.

Next, as shown in FIG. 11, using the plasma CVD method, SiO having a thickness of about 200 nm is used so as to cover the entire surface.₂After forming a film (not shown), SiO located on the upper surface and side surface of the p-side ohmic electrode 8₂By removing the film, SiO₂A current block layer 7 made of a film is formed.

Finally, as shown in FIG. 1, an Al layer having a thickness of about 6 nm (not shown) has a thickness of about 10 nm in a predetermined region on the back surface of the n-type GaN substrate 1 by using a vacuum vapor deposition method or the like. A Pd layer (not shown) having a thickness of about 300 nm and an Au layer (not shown) having a thickness of about 300 nm are sequentially formed. As a result, the n-side ohmic electrode 9 composed of the Al layer, the Pd layer and the Au layer is formed. In this way, the nitride-based semiconductor laser device according to the first embodiment is formed.

Next, the results of investigating the spread angle and luminous efficiency of the laser beam of the nitride-based semiconductor laser device according to the first embodiment actually manufactured according to the above manufacturing process will be described. In this first embodiment, it was found that the vertical spread angle θ1 and the horizontal spread angle θ2 of the laser beam are about 18 ° and about 10 °, respectively. That is, θ1 / θ2 = about 1.8, and it was confirmed that the shape of the laser beam approaches a perfect circle (θ1 / θ2 = 1). In addition, the luminous efficiency was about 1.5 W / A, and it was confirmed that high luminous efficiency could be obtained.

(Second Embodiment) FIG. 12 is a perspective view showing the structure of a nitride semiconductor laser device according to the second embodiment of the present invention. 13 and 14 are cross-sectional views taken along the lines 300-300 and 400-400 of FIG. 12, respectively. With reference to FIGS. 12 to 14, in this second embodiment, unlike the first embodiment, the center of the element other than the region near the resonator end face on the light emitting side so as to contact the p-side ohmic electrode. About the case where the sheet resistance value of the p-side ohmic electrode is about 10Ω / by forming the p-side pad electrode in the region including the region and making the thickness of the p-side ohmic electrode smaller than that of the first embodiment. explain. The nitride-based semiconductor laser device according to the second embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

In the nitride-based semiconductor laser device according to the second embodiment, as shown in FIG. 12, the n-side clad layer 2 and the active layer having the same composition and thickness as those of the first embodiment are placed on the n-type GaN substrate 1. 3 are formed in sequence. On the active layer 3, a p-side clad layer 24 having the same composition as the p-side clad layer 4 of the first embodiment is formed. The p-side clad layer 24 has a width of about 1.5 μm and has a striped (elongated) convex portion extending in the resonator direction. The p-side clad layer 24 is an example of the "second semiconductor layer" of the present invention.

Here, in the second embodiment, the flat portions 24a and 24b other than the convex portion of the p-side clad layer 24 include the region A2 near the resonator end face 20a on the light emitting side and the central region of the element other than the region A2. It has a different thickness than the region B2. Specifically, in the region A2, as shown in FIG. 13, the thickness tA2 of the flat portion 24a of the p-side clad layer 24 is about 60 nm, and the height of the convex portion from the upper surface of the flat portion 24a is about. It is 440 nm. Further, in the region B2, as shown in FIG. 14, the thickness tB2 of the flat portion 24b of the p-side clad layer 24 is about 150 nm, and the height from the upper surface of the flat portion 24b of the convex portion is about 350 nm. .. That is, the thickness tA2 (about 60 nm) of the flat portion 24a of the region A2 is smaller than the thickness tB2 (about 150 nm) of the flat portion 24b of the region B2. The regions A2 and B2 are examples of the "first region" and the "second region" of the present invention, respectively, and the flat portions 24a and 24b are the "first flat portion" and the "first flat portion" of the present invention, respectively. This is an example of "2 flat part". The length of the region A2 in the resonator direction is about 10 μm, and the length of the region B2 in the resonator direction is about 590 μm.

Further, as shown in FIG. 12, a contact layer 25 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side clad layer 24. The contact layer 25 is an example of the "second semiconductor layer" of the present invention. The contact layer 25 and the convex portion of the p-side clad layer 24 form a striped (elongated) ridge portion 26 having a width of about 1.5 μm and extending in the resonator direction. Further, on the upper surfaces of the flat portions 24a and 24b of the p-side clad layer 24 and on the side surfaces of the ridge portion 26, a current block layer 27 having the same composition and thickness as the current block layer 7 of the first embodiment is formed. It is formed.

Here, in the second embodiment, the p-side ohmic electrode 28 whose thickness is set so as to have a sheet resistance value of about 10 Ω / is formed on the contact layer 25 constituting the ridge portion 26. The p-side ohmic electrode 28 is composed of a Pt layer (not shown) having a thickness of about 1 nm and a Pd layer having a thickness of about 10 nm in order from the contact layer 25 side. The p-side ohmic electrode 28 is an example of the first electrode layer of the present invention. Further, in the second embodiment, the p-side pad electrode 30 is formed in the region B2 including the central region of the element other than the region A2 near the resonator end surface 20a on the light emitting side so as to contact the p-side ohmic electrode 28. ing. Specifically, the end portion 30a on the light emitting side of the p-side pad electrode 30 is arranged at a distance L2 of about 10 μm from the region A2 in the vicinity of the resonator end surface 20a on the light emitting side. The p-side pad electrode 30 has a Ti layer (not shown) having a thickness of about 100 nm, a Pd layer (not shown) having a thickness of about 200 nm, and a thickness of about 3 μm in order from the p-side ohmic electrode 28 side. It is composed of an Au layer (not shown) having. The p-side pad electrode 30 is an example of the "second electrode layer" of the present invention.

Further, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

Then, in the nitride-based semiconductor laser device according to the second embodiment, the light generated in the active layer 3 is reflected by the resonator end faces 20a and 20b to oscillate the laser.

Next, in the configuration of the nitride-based semiconductor laser device of the second embodiment, the sheet resistance value of the p-side ohmic electrode 28 is changed in three stages (about 10Ω / , about 1Ω / , and about 0.1Ω / ). The results of measuring MTTF (Mean Time To Failure) are shown in Table 2 below.

<tables num="2"><img file="JP2005294322A_D0002.tif" /></tables> With reference to Table 2 above, it was found that when the sheet resistance values of the p-side ohmic electrode 28 were about 10 Ω / and about 1 Ω / , the MTTF was as long as about 5000 hours and about 4000 hours, respectively. This is because the current does not easily flow in the resonator direction (horizontal direction) at the p-side ohmic electrode 28, so that the current flowing in the region A2 where the amount of crystal defects is larger than the region B2 including the central region of the device is reduced. It is probable that this was due to the fact that As a result, the increase in crystal defects caused by the flow of current through the crystal defect portion of the active layer 3 located in region A2 was suppressed, and it is considered that the MTTF was extended to about 4000 hours or more. On the other hand, when the sheet resistance value of the p-side ohmic electrode 28 was about 0.1 Ω / , it was found that the MTTF was as short as about 700 hours. From this result, it is considered that the MTTF can be lengthened to about 4000 hours or more by setting the sheet resistance value of the p-side ohmic electrode 28 to about 1Ω / or more.

In the second embodiment, as described above, the thickness tA2 (about 60 nm) of the flat portion 24a located in the region A2 near the end face 20a of the optical cavity on the light emitting side is set to the region B2 including the central region of the element other than the region A2. By making the thickness of the flat portion 24b located at the position smaller than tB2 (about 150 nm), the horizontal light confinement in the region A2 near the resonator end face 20a on the light emitting side is strengthened as in the first embodiment. Can be done. As a result, the horizontal spread of the laser beam emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle as in the first embodiment. In this case, when the convex portion (ridge portion 26) of the p-side clad layer 24 is formed by etching, the thickness tB2 (about 150 nm) of the flat portion 24b located in the region B2 of the p-side clad layer 24 is located in the region A2. Since the portion including the active layer 3 is not etched while being etched so as to be larger than the thickness tA2 (about 60 nm) of the flat portion 24a to be formed, the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made to. As a result, as in the first embodiment, the increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high luminous efficiency can be obtained. As described above, in the second embodiment, as in the first embodiment, a nitride-based semiconductor laser device having high luminous efficiency and capable of obtaining a laser beam shape close to a perfect circle is obtained. be able to.

Further, in the second embodiment, the p-side pad electrode 30 is formed in the region B2 including the central region of the element other than the region A2 near the resonator end surface 20a on the light emitting side so as to come into contact with the p-side ohmic electrode 28. As a result, the current can be injected from the p-side pad electrode 30 only into the region A2 near the resonator end face 20a on the light emitting side of the p-side ohmic electrode 28. In addition, by setting the sheet resistance value of the p-side ohmic electrode 28 to about 10Ω / , when a current is injected from the p-side pad electrode 30, the p-side ohmic electrode 28 has a current in the resonator direction (horizontal direction). The current density of the current flowing through the region A2 near the resonator end surface 20a on the light emitting side can be made smaller than the current density of the current flowing through the region B2 including the central region of the element other than the region A2. it can. As a result, even if the crystal defects of the active layer 3 located in the region A2 are larger than the crystal defects of the active layer 3 located in the region B2, the current flowing through the crystal defects portion of the active layer 3 located in the region A2. Can be reduced. As a result, it is possible to suppress an increase in crystal defects due to a large amount of current flowing through the crystal defect portion of the active layer 3, so that the life of the device can be extended. Further, by arranging the end portion 30a on the light emitting side of the p-side pad electrode 30 at a distance L2 of about 10 μm from the region A2 near the resonator end surface 20a on the light emitting side, the light emitting side can be easily arranged. The current density of the current flowing through the region A2 near the resonator end face 20a can be made smaller than the current density of the current flowing through the region B2 including the central region of the element other than the region A2. Specifically, the resistance value of the p-side ohmic electrode 28 having a length of about 10 μm is about 70 Ω, which is larger than the series resistance value (about 15 Ω) of the element. Therefore, in the p-side ohmic electrode 28 located between the end 30a of the p-side pad electrode 30 and the region A2, it is possible to make it difficult for the current to flow from the end 30a of the p-side pad electrode 30 toward the region A. it can.

Further, in the region A2 near the resonator end surface 20a on the light emitting side of the second embodiment, all the p-type AlGaN layers are etched in the p-side clad layer 24, and the optical guide layer is also etched to a depth in the middle. Has been done. Even if the etching depth is increased in this way, the above-mentioned effect can be obtained if the etching depth does not reach the active layer 3.

The other effects of the second embodiment are the same as those of the first embodiment.

Next, referring to FIG. 12, as the manufacturing process of the second embodiment, first, the current block layer 27 is formed by using the same process as that of the first embodiment shown in FIGS. 5 to 11. .. However, when forming the p-side ohmic electrode 28, a Pt layer (not shown) having a thickness of about 1 nm and a Pd layer having a thickness of about 10 nm are sequentially formed in order from the contact layer 25 side. After that, the p-side pad electrode 30 is formed in the region B2 including the central region of the device so as to come into contact with the p-side ohmic electrode 28 by using a vacuum vapor deposition method or the like. Specifically, the p-side pad is arranged so that the end portion 30a on the light emitting side of the p-side pad electrode 30 is arranged at a distance L2 of about 10 μm from the region A2 near the resonator end surface 20a on the light emitting side. Form the electrode 30. When forming the p-side pad electrode 30, a Ti layer having a thickness of about 100 nm (not shown) and a Pd layer having a thickness of about 200 nm (not shown) are formed in order from the p-side ohmic electrode 28 side. And an Au layer (not shown) having a thickness of about 3 μm is sequentially formed.

Finally, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 by using a vacuum vapor deposition method or the like. In this way, the nitride-based semiconductor laser device according to the second embodiment is formed.

Next, the results of investigating the spread angle and luminous efficiency of the laser beam of the nitride-based semiconductor laser device according to the second embodiment actually manufactured according to the above manufacturing process will be described. In this second embodiment, it was found that the vertical spread angle θ1 and the horizontal spread angle θ2 of the laser beam are about 18 ° and about 13 °, respectively. That is, θ1 / θ2 = about 1.4, and it was confirmed that the shape of the laser beam was closer to a perfect circle (θ1 / θ2 = 1) than in the first embodiment. In addition, the luminous efficiency was about 1.5 W / A, and it was confirmed that high luminous efficiency could be obtained as in the first embodiment.

(Third Embodiment) FIG. 15 is a perspective view showing the structure of a nitride semiconductor laser device according to the third embodiment of the present invention. 16 and 17 are cross-sectional views taken along the lines 500-500 and 600-600 of FIG. 15, respectively. With reference to FIGS. 15 to 17, in the third embodiment, unlike the first and second embodiments, the inclined portion is connected so as to connect the upper surfaces of the flat portions of the p-side clad layer having different thicknesses. Will be described. The nitride-based semiconductor laser device according to the third embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

In the nitride-based semiconductor laser device according to the third embodiment, as shown in FIG. 15, the n-side clad layer 2 and the active layer having the same composition and thickness as those of the first embodiment are placed on the n-type GaN substrate 1. 3 are formed in sequence. On the active layer 3, a p-side clad layer 44 having the same composition as the p-side clad layer 4 of the first embodiment is formed. The p-side clad layer 44 has a width of about 1.5 μm and has a striped (elongated) convex portion extending in the resonator direction. The p-side clad layer 44 is an example of the "second semiconductor layer" of the present invention.

Here, in the third embodiment, the flat portions 44a and 44b other than the convex portion of the p-side clad layer 44 include the region A3 near the resonator end face 40a on the light emitting side and the central region of the element other than the region A3. It has a different thickness than the region B3. Specifically, in the region A3, as shown in FIG. 16, the thickness tA3 of the flat portion 44a of the p-side clad layer 44 is about 100 nm, and the height of the convex portion from the upper surface of the flat portion 44a is about about 100 nm. It is 400 nm. Further, in the region B3, as shown in FIG. 17, the thickness tB3 of the flat portion 44b of the p-side clad layer 44 is about 150 nm, and the height from the upper surface of the flat portion 44b of the convex portion is about 350 nm. .. The regions A3 and B3 are examples of the "first region" and the "second region" of the present invention, respectively, and the flat portions 44a and 44b are the "first flat portion" and the "first flat portion" of the present invention, respectively. This is an example of "2 flat part". The length of the region A3 in the resonator direction is about 10 μm, and the length of the region B3 in the resonator direction is about 590 μm. Further, in the third embodiment, as shown in FIG. 15, the upper surface of the flat portion 44a and the upper surface of the flat portion 44b are connected between the flat portion 44a and the flat portion 44b of the p-side clad layer 44. , An inclined portion 44c having an inclination angle of about 60 ° is provided.

Further, a contact layer 45 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side clad layer 44. The contact layer 45 is an example of the "second semiconductor layer" of the present invention. The contact layer 45 and the convex portion of the p-side clad layer 44 form a striped (elongated) ridge portion 46 having a width of about 1.5 μm and extending in the resonator direction. Further, on the upper surfaces of the flat portions 44a and 44b of the p-side clad layer 44 and on the side surfaces of the ridge portion 46, a current block layer 47 having the same composition and thickness as the current block layer 7 of the first embodiment is formed. It is formed. Further, a p-side ohmic electrode 48 having the same composition and thickness as that of the first embodiment is formed on the contact layer 45 constituting the ridge portion 46.

Further, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

Then, in the nitride-based semiconductor laser device according to the third embodiment, the light generated in the active layer 3 is reflected by the resonator end faces 40a and 40b to oscillate the laser.

In the third embodiment, as described above, the thickness tA3 (about 100 nm) of the flat portion 44a located in the region A3 near the end face 40a of the resonator on the light emitting side is set to the region B3 including the central region of the element other than the region A3. By making the thickness of the flat portion 44b located at the position smaller than tB3 (about 150 nm), the horizontal light confinement in the region A3 near the resonator end face 40a on the light emitting side is strengthened as in the first embodiment. Can be done. As a result, the horizontal spread of the laser beam emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle as in the first embodiment. In this case, when the convex portion (ridge portion 46) of the p-side clad layer 44 is formed by etching, the thickness tB3 (about 150 nm) of the flat portion 44b located in the region B3 of the p-side clad layer 44 is located in the region A3. Since the portion including the active layer 3 is not etched while being etched so as to be larger than the thickness tA3 (about 100 nm) of the flat portion 44a to be formed, the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made to. As a result, as in the first embodiment, the increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high luminous efficiency can be obtained. As described above, in the third embodiment, as in the first embodiment, a nitride-based semiconductor laser device having high luminous efficiency and capable of obtaining a laser beam shape close to a perfect circle is obtained. be able to.

Further, in the third embodiment, an inclination angle of about 60 ° is set so as to connect the upper surface of the flat portion 44a and the upper surface of the flat portion 44b between the flat portion 44a and the flat portion 44b of the p-side clad layer 44. Since the boundary surface between the flat portion 44a and the flat portion 44b is inclined by providing the inclined portion 44c having the above, the case where the flat portion 44a and the flat portion 44b having different thicknesses are connected by the vertical boundary surface. In comparison with the above, light is less likely to be reflected in the direction of the resonator end face 40b on the side opposite to the light emitting side at the boundary surface. As a result, it is possible to suppress the generation of an unnecessary laser oscillation mode between the boundary surface between the flat portion 44a and the flat portion 44b and the resonator end surface 40a on the side opposite to the light emitting side. As a result, the laser oscillation mode having high luminous efficiency (laser oscillation mode between the resonator end face 40a on the light emitting side and the resonator end face 40b on the opposite side to the light emitting side) is maintained up to the high output region. Therefore, the luminous efficiency can be further improved. Further, the lower end portion (edge portion) of the boundary surface between the flat portion 44a and the flat portion 44b is smoother than the case where the flat portion 44a and the flat portion 44b having different thicknesses are connected by a vertical boundary surface. become. As a result, the light loss at the edge portion of the boundary surface between the flat portion 44a and the flat portion 44b can be suppressed, and thus the luminous efficiency can be further improved.

The other effects of the third embodiment are the same as those of the first embodiment.

18 to 20 are perspective views for explaining the manufacturing process of the nitride-based semiconductor laser device according to the third embodiment shown in FIG. Next, the manufacturing process of the nitride semiconductor laser device according to the third embodiment will be described with reference to FIGS. 15 and 18 to 20.

First, as shown in FIG. 18, predetermined regions of the p-side ohmic electrode 48, the contact layer 45, and the p-side clad layer 44 are etched using the same process as in the first embodiment shown in FIGS. 5 to 7. As a result, up to the convex portion of the p-side clad layer 44 is formed. After that, the resist 51 is formed so as to cover only the p-side clad layer 44, the contact layer 45, and the p-side ohmic electrode 48 located in the region B3 including the central region of the device. At this time, by controlling the exposure conditions and the like, the surface 51a of the resist 51 located at the boundary between the region A3 near the resonator end surface 40a (see FIG. 15) on the light emitting side and the region B3 including the central region of the device. However, the resist 51 is formed so as to have an inclination angle such that the inclination angle after etching is about 60 °.

Next, as shown in FIG. 19, Cl₂Using the RIE method using a system gas, using the p-side ohmic electrode 48 located in the region A3 as a mask, the resist 51 and the resist 51 until the thickness tA3 of the flat portion 44a located in the region A3 of the p-side clad layer 44 becomes about 100 nm. The p-side clad layer 44 is etched at the same time. As a result, the flat portions 44a and 44b other than the convex portion of the p-side clad layer 44 include the region A3 near the resonator end surface 40a (see FIG. 15) on the light emitting side and the region including the central region of the element other than the region A3. The thickness is different from that of B3. Specifically, in the region A3, the thickness tA3 of the flat portion 44a of the p-side clad layer 44 is about 100 nm, and the height from the upper surface of the flat portion 44a of the convex portion is about 400 nm. On the other hand, in the region B3, the thickness tB3 of the flat portion 44b of the p-side clad layer 44 is about 150 nm, and the height from the upper surface of the flat portion 44b of the convex portion is about 350 nm. Further, between the flat portion 44a and the flat portion 44b of the p-side clad layer 44, the inclined portion 44c having an inclination angle of about 60 ° so as to connect the upper surface of the flat portion 44a and the upper surface of the flat portion 44b. Is provided. As a result, the ridge portion 46 composed of the convex portion of the p-side clad layer 44 and the contact layer 45 is formed. After that, the resist 51 is removed to bring the resist 51 into the state shown in FIG.

Next, as shown in FIG. 15, using the same process as in the first embodiment shown in FIG. 11, the upper surfaces of the flat portions 44a and 44b of the p-side clad layer 44 and the side surfaces of the ridge portion 46. In addition, a current block layer 47 having the same composition and thickness as the current block layer 7 of the first embodiment is formed.

Finally, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 by using a vacuum vapor deposition method or the like. In this way, the nitride-based semiconductor laser device according to the third embodiment is formed.

(Fourth Embodiment) FIG. 21 is a perspective view showing the structure of a nitride semiconductor laser device according to the fourth embodiment of the present invention. FIG. 22 is a cross-sectional view taken along the lines 700-700 and 900-900 of FIG. 21, and FIG. 23 is a cross-sectional view taken along the line 800-800 of FIG. With reference to FIGS. 21 to 23, in the fourth embodiment, unlike the first to third embodiments described above, in the p-side clad layer, the region near the resonator end face on the side opposite to the light emitting side is also formed. A case where a flat portion having a thickness smaller than the thickness of the flat portion located in the region including the central region of the element is provided will be described. The nitride-based semiconductor laser device according to the fourth embodiment has a width W of about 300 μm and a resonator length L of about 600 μm, as in the first embodiment.

In the nitride-based semiconductor laser device according to the fourth embodiment, as shown in FIG. 21, the n-side clad layer 2 and the active layer having the same composition and thickness as those of the first embodiment are placed on the n-type GaN substrate 1. 3 are formed in sequence. On the active layer 3, a p-side clad layer 64 having the same composition as the p-side clad layer 4 of the first embodiment is formed. The p-side clad layer 64 has a width of about 1.5 μm and has a striped (elongated) convex portion extending in the resonator direction. The p-side clad layer 64 is an example of the "second semiconductor layer" of the present invention.

Here, in the fourth embodiment, the flat portions 64a, 64b, and 64c other than the convex portion of the p-side clad layer 64 resonate with the region A4 near the resonator end surface 60a on the light emitting side and the side opposite to the light emitting side. The region C4 near the end face 60b and the region B4 including the central regions of the elements other than the regions A4 and C4 have different thicknesses. Specifically, in regions A4 and C4, as shown in FIG. 22, the thickness tA4 of the flat portions 64a and 64c of the p-side clad layer 64 is about 100 nm, and is from the upper surface of the flat portions 64a and 64c of the convex portion. The height of is about 400 nm. Further, in the region B4, as shown in FIG. 23, the thickness tB4 of the flat portion 64b of the p-side clad layer 64 is about 150 nm, and the height from the upper surface of the flat portion 64b of the convex portion is about 350 nm. .. That is, the thickness tA4 (about 100 nm) of the flat portions 64a and 64c of the regions A4 and C4 is smaller than the thickness tB4 (about 150 nm) of the flat portion 64b of the region B4. The regions A4, B4 and C4 are examples of the "first region", "second region" and "third region" of the present invention, respectively, and the flat portions 64a, 64b and 64c are the present invention, respectively. This is an example of the "first flat portion", "second flat portion", and "third flat portion" of the above. The length of the regions A4 and C4 in the resonator direction is about 10 μm, and the length of the region B4 in the resonator direction is about 580 μm.

Further, as shown in FIG. 21, a contact layer 65 having the same composition and thickness as the contact layer 5 of the first embodiment is formed on the convex portion of the p-side clad layer 64. The contact layer 65 is an example of the "second semiconductor layer" of the present invention. The contact layer 65 and the convex portion of the p-side clad layer 64 form a striped (elongated) ridge portion 66 having a width of about 1.5 μm and extending in the resonator direction. Further, the upper surfaces of the flat portions 64a, 64b and 64c of the p-side clad layer 64 and the side surfaces of the ridge portion 66 are current block layers having the same composition and thickness as the current block layer 7 of the first embodiment. 67 is formed. Further, a p-side ohmic electrode 68 having the same composition and thickness as that of the first embodiment is formed on the contact layer 65 constituting the ridge portion 66.

Further, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1.

Then, in the nitride-based semiconductor laser device according to the fourth embodiment, the light generated in the active layer 3 is reflected by the resonator end faces 60a and 60b to oscillate the laser.

In the fourth embodiment, as described above, the thickness tA4 (about 100 nm) of the flat portion 64a located in the region A4 near the end face 60a of the optical cavity on the light emitting side is set to the region B4 including the central region of the element other than the region A4. By making the thickness of the flat portion 64b located at the position smaller than tB4 (about 150 nm), the horizontal light confinement in the region A4 near the resonator end face 60a on the light emitting side is strengthened as in the first embodiment. Can be done. As a result, the horizontal spread of the laser beam emission spot can be reduced, so that the horizontal spread angle θ2 of the laser light can be increased. As a result, the shape of the laser beam can be made close to a perfect circle as in the first embodiment. In this case, when the convex portion (ridge portion 66) of the p-side clad layer 64 is formed by etching, the thickness tB4 (about 150 nm) of the flat portion 64b located in the region B4 of the p-side clad layer 64 is located in the region A4. Since the flat portion 64a is etched so as to be larger than the thickness tA4 (about 100 nm) and the portion including the active layer 3 is not etched, the amount of crystal defects in the active layer 3 is reduced as in the first embodiment. Can be made to. As a result, as in the first embodiment, the increase in light absorption due to the crystal defect portion of the active layer 3 can be suppressed, so that a nitride-based semiconductor laser device having high luminous efficiency can be obtained. As described above, in the fourth embodiment, as in the first embodiment, a nitride-based semiconductor laser device having high luminous efficiency and capable of obtaining a laser beam shape close to a perfect circle is obtained. be able to.

Further, in the fourth embodiment, the flat portion having a thickness tA4 (about 100 nm) smaller than the thickness tB4 (about 150 nm) of the flat portion 64b also in the region C4 near the resonator end face 60b on the side opposite to the light emitting side. By providing 64c, even if the resonator end surface 60b on the side opposite to the light emitting side is used as the light emitting surface, the shape of the laser beam can be made close to a perfect circle. As a result, the shape of the laser beam can be made closer to a perfect circle regardless of which of the two resonator end faces 60a and 60b is used as the light emitting surface. As a result, it is possible to manufacture a semiconductor laser device capable of obtaining a laser beam shape close to a perfect circle regardless of which of the resonator end faces 60a and 60b is set as the light emitting surface when assembling the device. it can.

24 to 26 are perspective views for explaining the manufacturing process of the nitride semiconductor laser device according to the fourth embodiment shown in FIG. 21. Next, the manufacturing process of the nitride semiconductor laser device according to the fourth embodiment will be described with reference to FIGS. 21 and 24 to 26.

First, as shown in FIG. 24, predetermined regions of the p-side ohmic electrode 68, the contact layer 65, and the p-side clad layer 64 are etched using the same process as in the first embodiment shown in FIGS. 5 to 7. As a result, up to the convex portion of the p-side clad layer 64 is formed. After that, the resist 71 is formed so as to cover only the p-side clad layer 64, the contact layer 65, and the p-side ohmic electrode 68 located in the region B4 including the central region of the device.

Next, Cl₂Using the RIE method using a system gas, a predetermined region from the upper surface of the flat portion 64b of the p-side clad layer 64 to a depth of about 50 nm using the resist 71 and the p-side ohmic electrodes 68 located in the regions A4 and C4 as masks. To remove. As a result, the flat portions 64a, 64b, and 64c other than the convex portion of the p-side clad layer 64 are formed in the region A4 near the resonator end face 60a (see FIG. 21) on the light emitting side and the resonator on the opposite side to the light emitting side. The thickness is different between the region C4 near the end face 60b (see FIG. 21) and the region B4 including the central regions of the elements other than the regions A4 and C4. Specifically, in the regions A4 and C4, the thickness tA4 of the flat portions 64a and 64c of the p-side clad layer 64 is about 100 nm, and the height from the upper surface of the flat portions 64a and 64c of the convex portion is about 400 nm. On the other hand, in the region B4, the thickness tB4 of the flat portion 64b other than the convex portion of the p-side clad layer 64 is about 150 nm, and the height from the upper surface of the flat portion 64b of the convex portion is about 350 nm. As a result, the ridge portion 66 composed of the convex portion of the p-side clad layer 64 and the contact layer 65 is formed. After that, the resist 71 is removed to bring the resist 71 into the state shown in FIG.

Next, as shown in FIG. 21, the upper surfaces of the flat portions 64a, 64b and 64c of the p-side clad layer 64 and the side surfaces of the ridge portion 66 are used in the same process as in the first embodiment shown in FIG. A current block layer 67 having the same composition and thickness as the current block layer 7 of the first embodiment is formed on the top.

Finally, an n-side ohmic electrode 9 having the same composition and thickness as that of the first embodiment is formed in a predetermined region on the back surface of the n-type GaN substrate 1 by using a vacuum vapor deposition method or the like. In this way, the nitride-based semiconductor laser device according to the fourth embodiment is formed.

It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the above-described embodiment, and further includes all modifications within the meaning and scope equivalent to the scope of claims.

For example, in the first to fourth embodiments described above, the case where the present invention is applied to a semiconductor laser device made of a nitride-based semiconductor has been described, but the present invention is not limited to this, and is made of a semiconductor other than the nitride-based semiconductor. It can also be applied to semiconductor laser devices.

Further, in the first to fourth embodiments, the length of the region near the end face of the resonator on the light emitting side in the resonator direction is set to about 10 μm, but the present invention is not limited to this, and the length on the light emitting side is not limited to this. The length of the region near the end face of the resonator in the resonator direction may be within the range of about 3 μm or more and 50 μm or less.

Further, in the first, third and fourth embodiments, the thickness of the flat portion located in the region including the central region of the element of the p-side clad layer is set to about 150 nm, but the present invention is not limited to this. If the thickness of the flat portion located in the region including the central region of the element of the p-side clad layer is set to about 100 nm or more and about 250 nm or less, the luminous efficiency can be increased and the threshold current can be lowered. can do.

Further, in the second embodiment, the end 30a on the light emitting side of the p-side pad electrode 30 is arranged at a distance L2 of about 10 μm from the region A2 near the end face 20a of the resonator on the light emitting side. The invention is not limited to this, and if the end of the p-side pad electrode on the light emitting side does not reach the end face of the resonator, the end of the p-side pad electrode on the light emitting side is near the end face of the cavity on the light emitting side. It may be placed in the area.

Further, in the second embodiment, the sheet resistance value of the p-side ohmic electrode is set to about 10 Ω / , but the present invention is not limited to this, and the sheet resistance value of the p-side ohmic electrode is set to about 1 Ω / . With the above settings, MTTF (Mean Time Between Failures) can be lengthened. Thereby, the life of the element can be extended.

Further, in the third embodiment, an inclined portion having an inclination angle of about 60 ° is provided so as to connect the upper surfaces of the flat portions of the p-side clad layers having different thicknesses, but the present invention is not limited to this. Instead, the upper surfaces of the flat portions of the p-side clad layers having different thicknesses may be connected by inclined portions having an inclination angle other than about 60 °.

<figref num="1">It is a perspective view which showed the structure of the nitride-based semiconductor laser device by 1st Embodiment of this invention.</figref><figref num="2">It is sectional drawing along the line 100-100 of FIG.</figref><figref num="3">It is sectional drawing along the line 200-200 of FIG.</figref><figref num="4">It is a graph which showed the spread angle in the horizontal direction of a laser beam when the length in the resonator direction of the region near the end face of a resonator on the light emission side was changed.</figref><figref num="5">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="6">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="7">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="8">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="9">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="10">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="11">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device by 1st Embodiment shown in FIG.</figref><figref num="12">It is a perspective view which showed the structure of the nitride-based semiconductor laser device by 2nd Embodiment of this invention.</figref><figref num="13">It is sectional drawing along the line 300-300 of FIG.</figref><figref num="14">It is sectional drawing along the line 400-400 of FIG.</figref><figref num="15">It is a perspective view which showed the structure of the nitride-based semiconductor laser device by the 3rd Embodiment of this invention.</figref><figref num="16">It is sectional drawing along the line 500-500 of FIG.</figref><figref num="17">It is sectional drawing along the line 600-600 of FIG.</figref><figref num="18">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 3rd Embodiment shown in FIG.</figref><figref num="19">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 3rd Embodiment shown in FIG.</figref><figref num="20">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 3rd Embodiment shown in FIG.</figref><figref num="21">It is a perspective view which showed the structure of the nitride-based semiconductor laser device according to 4th Embodiment of this invention.</figref><figref num="22">It is sectional drawing along the line 700-700 and line 900-900 of FIG.</figref><figref num="23">It is sectional drawing along the line 800-800 of FIG.</figref><figref num="24">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 4th Embodiment shown in FIG.</figref><figref num="25">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 4th Embodiment shown in FIG.</figref><figref num="26">It is a perspective view for demonstrating the manufacturing process of the nitride-based semiconductor laser device according to 4th Embodiment shown in FIG.</figref><figref num="27">It is a perspective view which showed the structure of the conventional semiconductor laser element.</figref><figref num="28">It is a side view for demonstrating the vertical spread angle of the laser beam of the conventional semiconductor laser element shown in FIG. 27.</figref><figref num="29">It is a top view for demonstrating the horizontal spread angle of the laser beam of the conventional semiconductor laser element shown in FIG. 27.</figref>

Code description

2 n-side clad layer (first semiconductor layer) 3 Active layer 4, 24, 44, 64 p-side clad layer (second semiconductor layer) 4a, 24a, 44a, 64a Flat part (first flat part) 4b, 24b, 44b, 64b Flat part (2nd flat part) 5, 25, 45 Contact layer 28 p side ohmic electrode (1st electrode layer) 30 p side pad electrode (2nd electrode layer) 64c Flat part (3rd flat part) A1 , A2, A3, A4 area (1st area) B1, B2, B3, B4 area (2nd area) C4 area (3rd area)