GaN SEMICONDUCTOR LASER DEVICE

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to an improvement of a GaN-based semiconductor laser device suitable for application to a light source such as an optical information device.

【0002】

[Conventional technology]

GaN-based semiconductors composed of compounds of group III elements such as Al, Ga, and In and group V element N are expected as semiconductors for light emitting devices and power devices from the viewpoint of their energy band structure and chemical stability. And its application has been tried. For example, attempts have been made to manufacture a blue semiconductor laser by laminating a plurality of GaN-based semiconductor layers on a sapphire substrate or a GaN substrate.

【0003】

Among these blue-green semiconductor lasers, an example in which light is confined and laser oscillated by forming a ridge type waveguide and causing a difference in refractive index in a direction parallel to the semiconductor junction surface is shown in FIG. (For example, Jpn. J. Appl. Phys., Vol.37 (1998) pp.L309-L312 and Jpn. J. Appl. Phys., Vol.39 (2000) pp.L647 -See L650 etc.).

【0004】

In the GaN-based semiconductor laser 500 of FIG. 11, a GaN thick film is formed on the (0001) plane sapphire substrate (not shown), and then the sapphire substrate is removed, and the GaN thick film is formed on the (0001) plane GaN substrate 501. It is used as. On the GaN substrate 501, n-type GaN contact layer 503, n-type AlGaN clad layer 504, n-type GaN guide layer 505, multiple quantum well active layer 506 using InGaN, p-type AlGaN evaporation prevention layer 507, p-type GaN. The guide layer 508, the p-type AlGaN clad layer 509, and the p-type GaN contact layer 510 are sequentially laminated.

【0005】

In this semiconductor laser 500, a ridge stripe 511 including the upper part of the p-type AlGaN clad layer 509 and the p-type GaN contact layer 510 is formed, and a difference in refractive index is created in a direction parallel to the semiconductor junction surface. A striped waveguide is provided to confine the horizontal and horizontal modes.

【0006】

SiO that does not absorb light from the active layer 506 on both sides of the ridge stripe 511₂The dielectric film 513 is formed, and a current constriction structure for injecting current only from the top of the ridge stripe is formed. Further, the refractive index of the ridge stripe portion 511 is higher than that of both side portions thereof, and the step-shaped refractive index distribution is formed in the direction parallel to the semiconductor junction surface.

【0007】

On top of ridge stripe 511 and SiO₂A p-type electrode 515 is formed on the dielectric film 513, and an n-type electrode 517 is formed on an n-type GaN contact layer 503 partially exposed by reactive ion etching (RIE), and these electrodes are semiconductors. It plays the role of injecting current into the laser 500.

【0008】

In this semiconductor laser 500, the end face of the resonator is further formed by dry etching, light is confined by the stepped refractive index distribution in the ridge stripe portion 511, and stable horizontal transverse mode oscillation is obtained with a low threshold current. In addition, the life of the semiconductor laser has reached 10,000 hours or more, and it is considered that the technology is almost completed from the viewpoint of extending the life of the laser and improving the reliability accordingly.

【0009】

[Problems to be Solved by the Invention]

However, if the laser with the structure shown in Fig. 11 is oscillated to the region where the light output is high, the linearity of the current-light output (IL) characteristics will be impaired in the process of increasing the injection current, and the light output will be reduced. It is known that a stepwise change in light output called a kink may appear because it is no longer proportional to the increase in current. When the laser element produces a kink, the laser beam moves in the emission direction and the output fluctuates, which causes a serious problem in practical use of the laser. And kink is considered to be closely related to the stability of horizontal transverse mode. There are two possible causes for kink, for example:

【0010】

First, In, which is frequently used as an active layer for GaN-based lasers._xGa_1-xAt N (0 x 1), regions having different In composition ratios are likely to be formed, which causes carriers to be localized and kink to occur. Secondly, since the effective mass of carriers is large in GaN-based materials, localization of carriers occurs, which causes kink. Therefore, in order to prevent kinking, a GaN-based semiconductor needs to be designed differently from other semiconductor materials in consideration of its unique physical properties.

【0011】

In order to prevent the occurrence of kink, it is effective to narrow the width of the striped waveguide, but at the same time, the current inflow path is also narrowed, so that the operating voltage rises and heat is generated accordingly, so the life of the laser And the problem of poor reliability arises. Therefore, there has been a demand for a structure that maintains the stability of the transverse mode without narrowing the current inflow path as much as possible.

【0012】

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a GaN-based laser element suitable for application to an optical pickup or the like with a high yield.

【0013】

[Means for solving problems]

According to the present invention, a GaN-based semiconductor laser device including a first conductive semiconductor layer, a semiconductor active layer, and a second conductive semiconductor layer stacked in this order emits light in a lateral direction intersecting the longitudinal direction of the resonator. This current injection window is made by including a built-in high refraction region provided so as to generate a confining refraction difference and a current injection window provided above the built-in high refraction region. It is characterized by including a narrow portion that is partially narrowed with respect to the width of the attached high refraction region.

【0014】

In addition, in order to generate a built-in high refraction region, it is preferable to provide a ridge stripe, and the current injection window portion is formed on the ridge stripe, and a narrow portion partially narrowed with respect to the stripe width is formed. It is preferable to include it. Further, the ridge embedding layer may be further laminated so as to embed the ridge stripe.

【0015】

The number of narrow portions of the current injection window portion is preferably in the range of 1 to 10. Further, the width W0 of the built-in high refractive index region is preferably within the range of 1 μm W0 4 μm. Further, in the current injection window portion, the narrow portion has a width W2 and the portion other than the narrow portion has a width W1, 1 μm W1 4 μm, 0.3 μm W1-W2 0.35 μm, and 0 μm <W2. It is preferable that the above conditions are satisfied.

【0016】

The active layer in the GaN-based semiconductor laser device is In_xGa_1-xIt preferably consists of N (0 x 1). Further, in the active layer, a part of N may be replaced with As or P.

【0017】

When manufacturing a GaN-based semiconductor laser device including a ridge stripe, it is preferable to form the ridge stripe after forming the current injection window portion.

【0018】

BEST MODE FOR CARRYING OUT THE INVENTION

(Definition of terms) First, the meanings of some terms used in the present specification will be clarified.

【0019】

In the specification of the present application, the "GaN-based semiconductor" means a nitride-based compound semiconductor having a hexagonal structure containing a compound of a group V element N and a group III element, and Al._xGa_yIn_1-xyIn addition to substances represented by the composition ratio of N (0 x 1; 0 y 1; 0 x + y 1), some of the Group III elements (about 20% or less) are other III. It also includes substances substituted with group elements (for example, B) and substances in which some of the group V elements (about 20% or less) are replaced with other group V elements (for example, P, As), and further about several percent. It also contains substances containing the same dopants (eg Zn, Mg, Si, Ge, etc.).

【0020】

The GaN-based substrate means a substrate made of a GaN-based semiconductor. Further, when a wafer in which a plurality of desired semiconductor layers are laminated after depositing a GaN-based semiconductor thick film on a dissimilar substrate containing a substance other than a GaN-based semiconductor as a main component is produced, and then the dissimilar substrate is removed. , The GaN-based semiconductor thick film is also included in the category of GaN-based substrates.

【0021】

The "width" of a ridge stripe means the width at the bottom of the ridge stripe and is measured along a direction orthogonal to the longitudinal direction of the ridge stripe. The bottom of the ridge stripe refers to the deposition start side of the semiconductor layer. The width is defined in this way because the width may differ between the bottom and the top of the ridge stripe due to the convenience of the manufacturing method.

【0022】

(Embodiment 1) First, the present inventors investigated to what extent the problem occurred in the laser device having the conventional structure shown in FIG. When the present inventors have produced a laser element having a structure similar to that shown in FIG. 11 and oscillate the laser to a region where the light output is high, there are 5 elements in which a kink appears within a range of 0 mW to 40 mW. It occurred as often as 60%. One of the applied products of GaN-based semiconductor lasers is a light source of an optical information recording device. When a laser element is used for such an application, an optical output of several mW to 40 mW is required, and it has been found that it is necessary to improve the yield of an element that does not cause kink within an optical output range of 40 mW or less.

【0023】

Embodiment 1 based on the above investigation will be described below with reference to the drawings. In addition, in each figure of this application, the same reference numeral is attached to the same part or the corresponding part. In the perspective view of FIG. 1, the plan view of FIG. 2, and the cross-sectional view of FIG. 3, the GaN-based semiconductor laser device according to the first embodiment is schematically illustrated. The dotted line in FIG. 1 represents the dielectric film 113 hidden under the p electrode 115. In FIG. 2, only the portion corresponding to the mesa portion 116 is shown, and the region adjacent to the portion is not shown. Further, in order to make the features of the first embodiment easy to understand, in FIG. 2, only the portion of the p electrode 115 in contact with the p-GaN contact layer 110 is drawn.

【0024】

In manufacturing the laser device of the first embodiment, first, a GaN substrate 101 having a thickness of 100 to 500 μm (for example, 400 μm) having a (0001) main surface for crystal growth is washed, and then hydrogen (H) is charged in the MOCVD apparatus.₂) Perform high temperature cleaning at about 1100 ° C in the atmosphere. Then cool down and H₂Carrier gas and silane (SiH)₄), Ammonia (NH₃), And trimethylgallium (TMG) are introduced into the reaction chamber to grow an n-GaN buffer layer 102 with a thickness of 10 nm to 10 μm (eg 100 nm) under a substrate temperature of about 600 ° C. Since the buffer layer 102 is provided for the purpose of alleviating the surface strain of the GaN substrate 101 and improving (flattening) surface morphology and unevenness, it may be omitted if the GaN substrate 101 has excellent crystallinity. ..

【0025】

Then N₂And NH₃Raise the substrate temperature to about 1050 ° C while introducing, and then add N carrier gas.₂From H₂TMG and SiH instead₄Is introduced to grow the n-type GaN contact layer 103 to a thickness of 0.1 to 10 μm (for example, 4 μm).

【0026】

After that, TMG and trimethylaluminum (TMA) were introduced in a fixed ratio, and n-type Al having a thickness of 0.5 to 1.0 μm (for example, 0.9 μm) was introduced._0.1Ga_0.9The n-AlGaN clad layer 104 is formed by depositing the N layer. Then, the supply of TMA is stopped and TMG is introduced to grow the n-type GaN guide layer 105 to a thickness of 50 to 200 nm (for example, 100 nm).

【0027】

Next, stop the supply of TMG and change the carrier gas to H.₂From N again₂Instead, lower the substrate temperature to 700 ° C, introduce trimethylindium (TMI) and TMG, and in_vGa_1-vA barrier layer (not shown) consisting of N (0 v 1) is grown. Subsequently, the supply of TMI is increased to a predetermined amount, and In_wGa_1-wA quantum well layer (not shown) consisting of N (0 w 1) is grown. By repeating this process, an InGaN multiple quantum well active layer 106 composed of an alternating laminated structure of an InGaN barrier layer and an InGaN well layer (barrier layer / well layer / ... well layer / barrier layer) is formed. The composition ratio and film thickness of InGaN that forms the barrier layer and the well layer are designed so that the emission wavelength is in the range of 370 to 430 nm, and 2 to 6 well layers (3 layers are most preferable) are formed. ..

【0028】

After the formation of the InGaN multiple quantum well active layer 106, the supply of TMI and TMG was stopped, the substrate temperature was raised to 1050 ° C again, and the carrier gas was N.₂From H again₂Instead of TMG, TMA, and the p-type doping agent biscyclopentadienyl magnesium (Cp)₂Mg) is introduced and p-Al with a thickness of 0 to 20 nm (for example, 10 nm) is introduced._0.2Ga_0.8By depositing N, the p-AlGaN anti-evaporation layer 107 is formed. This evaporation prevention layer may be omitted in some cases. Next, the supply of TMA is stopped and the supply amount of TMG is adjusted to grow the p-GaN optical guide layer 108 having a thickness of 50 to 200 nm (for example, 100 nm). Subsequently, TMA is introduced at a constant rate to adjust the flow rate of TMG, and p-type Al having a thickness of 0.5 to 1.0 μm (for example, 0.5 μm) is used._0.1Ga_0.9The p-AlGaN clad layer 109 is formed by depositing the N layer.

【0029】

After that, the supply of TMA is stopped and the supply amount of TMG is adjusted to grow the p-GaN contact layer 110 having a thickness of 0.01 to 10 μm (for example, 0.1 μm). Once this growth is over, TMG and Cp₂The supply of Mg is stopped, the substrate temperature is lowered to room temperature, and the obtained wafer is taken out from the MOCVD apparatus.

【0030】

Subsequently, the obtained wafer is processed to be a laser element. First, when forming the p-electrode portion, a striped resist pattern having a width of 4 μm is formed on the p-type contact layer 110 along the <1-100> direction of the GaN substrate 101, and the ridge stripe portion 111 is formed by RIE. ..

【0031】

After that, the resist is once peeled off, and a resist pattern including the width W1 = 3 μm of the wide part of the current injection window 114 and the width W2 = 1.9 μm of the narrow part is newly formed on the ridge stripe 111, and SiO₂By depositing the film, a dielectric film 113 for current constriction is formed. Next, the resist is peeled off, a window portion 114 is provided on the dielectric film 113 to partially expose the p-type GaN contact layer 110, and the p-electrode 115 is formed by vapor deposition in the order of Pd / Mo / Au. As the p electrode material, Pd / Pt / Au, Pd / Au, or Ni / Au may also be used. Next, after forming the protective film of the resist, the mesa portion 116 is formed by the dry etching method to expose a part of the n-type GaN contact layer 102, and the exposed portion is vapor-deposited in the order of Ti / Al. To form the n electrode 117. As the n-electrode material, Hf / Al, Ti / Mo, or Hf / Au may also be used.

【0032】

A resonator end face is produced by cleaving the wafer produced up to the n electrode, and further divided in parallel in the longitudinal direction of the resonator to obtain a laser element chip. At this time, the cavity length is set to, for example, 650 μm.

【0033】

In FIGS. 1 and 2 of the first embodiment, for example, the width W0 of the ridge stripe 111 is set to 4 μm, the width W1 of the wide portion of the current injection window 114 is set to 3 μm, and the width W2 of the narrow portion is set to 1.9 μm. To. The number of narrow portions of the current injection window 114 is 3, and the length L1 of this narrow portion is set to 30 μm, and the length L2 of the transition portion from the wide portion to the narrow portion is set to 10 μm.

【0034】

In the GaN-based laser device 100 as shown in FIG. 3, the horizontal light field corresponds to the ridge stripe 111 due to the difference in the effective refractive index between the portion corresponding to the ridge stripe 111 and the portions on both sides thereof. Confined in the portion, a so-called real refractive index waveguide is realized. Then, with this GaN-based laser, horizontal transverse mode oscillation with an oscillation wavelength of 405 nm can be obtained. Further, since the narrow portion is formed in the current injection window portion 114 provided on the ridge stripe 111, the kink level can be increased by about 10 mW or more as compared with the conventional case.

【0035】

When the narrow portion of the current injection window 114 is not provided, the peak wavelength shifts when the light output of the laser is increased, or a mode including a plurality of peak wavelengths is established. However, in the narrow portion of the current injection window portion 114, light is absorbed without gain being obtained in the large gap between the window portion and the side end of the waveguide, so that the central portion in the width direction of the waveguide is used. Only the basic mode with a single peak can be set up, and the basic mode can be set up stably for the entire waveguide. This makes it possible to increase the yield of laser elements that do not generate kink up to 40 mW to about 80%.

【0036】

Furthermore, the threshold voltage of this GaN-based laser device can be made about 10% lower than that of a GaN-based laser device that has a narrow striped waveguide and a window with a uniform width so as to have a similar kink level. is there.

【0037】

In order to obtain a GaN-based laser device having such an effect, the total length of the narrow portion of the current injection window 114 is designed to be 1/2 or less of the resonator length. If the narrow portion has a longer length than this, the operating voltage of the element becomes high due to the influence of the narrow portion, which is not preferable. In the present embodiment, the length of each narrow portion is set to a constant L1, but the length of each narrow portion may be different from each other. Further, as long as the condition that the total length of the narrow portion is 1/2 or less of the cavity length is satisfied, the ratio of the narrow portion length L1 and the transition portion length L2 may be changed. In extreme cases, L2 = 0 may be set. Further, the transition portion from the wide portion to the narrow portion does not have to be a straight line, and may be a curved line.

【0038】

The width W0 of the ridge stripe 111 is designed so that 1 μm W0 4 μm. If W0 is less than 1 μm, the area that can be taken as the current injection part is limited small from the beginning, which causes an increase in the operating voltage. On the contrary, if W0 is made larger than 4 μm, the width of the ridge waveguide becomes wider and it becomes easier to establish a mode including a plurality of peaks.

【0039】

The width W1 of the wide portion and the width W2 of the narrow portion of the current injection window 114 are designed so as to satisfy the conditions of 1 μm W1 4 μm, 0.3 μm W1-W2 3.5 μm, and 0 μm <W2. In order to obtain the effect of preventing kink, the value of W1-W2 needs to be about 0.3 μm, but when W2 becomes 0, the mode cannot be set. In addition, in consideration of increasing the light absorption effect described above and preventing the operating voltage of the element from rising, if the total length of the narrow portion is long, set the value of W1-W2 to a small value, and vice versa. You can set a large value for W1-W2. At this time, the total length of the narrow portions may be increased by increasing the number of narrow portions, but if the number of narrow portions increases, the change in the ridge stripe width per unit length of the ridge stripe changes. It becomes larger, the propagating mode is scattered, and the threshold voltage rises. Since the number of narrow portions accompanied by an increase in the threshold value is about 10 or more, the number of narrow portions may be set to about 10 or less.

【0040】

Although FIGS. 1 and 2 are drawn so as to have a gap between the wide portion of the current injection window 114 and the side surface of the ridge stripe 111, this gap may not be provided. Further, in FIGS. 1 and 3, the side surface of the ridge stripe 111 is drawn so as to be perpendicular to the main surface of the GaN-based semiconductor layer, but the side surface may be inclined.

【0041】

Further, in a GaN-based laser device in which As or P is mixed in the active layer, the transverse mode is likely to be disturbed due to the local fluctuation of the composition ratio of As or P. In this case as well, the narrowness of the current injection window 114 is narrow. It is possible to raise the kink level by the presence of the part.

【0042】

(Embodiment 2) FIG. 4 is similar to FIG. 2, but schematically illustrates the GaN-based semiconductor laser device 200 according to the second embodiment. FIG. 3 can be referred to as a cross-sectional view of the GaN-based semiconductor laser device 200.

【0043】

The first difference between the second embodiment and the first embodiment is that the ridge stripe width is 2.5 μm. In this case, since the ridge stripe width is narrower than that of the first embodiment, it is more effective in improving the kink level.

【0044】

The second difference between the second embodiment and the first embodiment is that the current injection window portion 114 is manufactured with a wide portion width W1 = 2.5 μm and a narrow portion width W2 = 1.2 μm. .. Further, in the second embodiment, as shown in FIG. 4, the p electrode 115 is provided with an effective narrow portion on the laser beam emitting surface side and the reflecting surface side. The length L1 of the narrow portion is 50 μm, and the length L2 of the transition portion from the wide portion to this narrow portion is 20 μm.

【0045】

The third difference between the second embodiment and the first embodiment is that the resonator end face of the laser is formed by a dry etching method.

【0046】

The fourth difference between the second embodiment and the first embodiment is that the resonator length of the laser is set to 450 μm.

【0047】

The kink level of the GaN-based laser device 200 configured as described above is the same as in the case of the first embodiment, and the yield of the device in which kink does not occur up to 40 mW is about 80% or more as in the case of the first embodiment. Become. Further, the threshold voltage of the element of the second embodiment is also the same as that of the first embodiment. Further, in the element of the second embodiment, since the narrow portion of the current injection window portion 114 is present on the light emitting end face, the horizontal far field pattern (FFP) of the emitted laser light becomes wide. Such a laser element can be preferably used in an optical recording / reproduction device or the like.

【0048】

It is generally known that the FFP becomes an elliptical shape that is long in the vertical direction because the end face of the active region on the laser beam emitting surface is much wider in the direction parallel to the semiconductor junction surface than in the vertical direction. However, by narrowing down the part where the current is injected near the end face of the resonator, the region where the gain is generated by the current injection is also narrowed down, so that the substantial width of the active layer can be narrowed in the direction parallel to the junction surface, and the ellipse. The horizontal direction of the FFP pattern of the shape can be widened to approach a circle.

【0049】

In the second embodiment, the narrow portions of the current injection window 114 are provided at two locations, the laser beam emitting side and the reflecting side, but may be provided at a larger number of locations, or only on the emitting surface side. It may be provided in.

【0050】

(Embodiment 3) FIGS. 5 and 6 are similar to FIGS. 2 and 3, respectively, but schematically illustrate the GaN-based semiconductor laser device 300 according to the third embodiment.

【0051】

The first difference between the third embodiment and the first and second embodiments is that the ridge stripe 111 having a width W0 = 3 μm is embedded in the embedded layer 118, and the window portion for current injection in the dielectric film 113 on the ridge stripe. 114 plays the role of current constriction, on which a second p-GaN contact layer 119 and p electrode 115 are formed.

【0052】

The second difference between the third embodiment and the first and second embodiments is that the current injection window 114 is manufactured with a wide portion width W1 = 2.2 μm and a narrow portion width W2 = 1.3 μm. Is. Further, in the third embodiment, as shown in FIG. 5, narrow portions of the current injection window portion 114 are provided on the laser beam emitting surface side and the reflecting surface side. The length L1 of the narrow portion is 60 μm, and the length L2 of the transition portion from the wide portion to the narrow portion is 30 μm.

【0053】

In order to manufacture the laser element of the third embodiment, the same process as in the case of the first embodiment is performed until the ridge stripe 111 is formed. Then SiO covering the ridge stripe 111₂With the mask (not shown) attached, the MOCVD method was used again to n-type Al._0.1Ga_0.9The N-embedded layer 118 is deposited until its top surface is thick enough to match the top surface of the ridge stripe 111. At this time, the upper surface of the embedded layer 118 is adjusted so as to be within ± 0.1 μm from the top surface of the ridge stripe 111. If adjusted to this range, the subsequent formation of the window portion 114 becomes easy.

【0054】

Next, SiO covering the ridge stripe 111₂The mask is peeled off to form a resist pattern having a wide portion width W1 = 2.2 μm and a narrow portion width W2 = 1.3 μm on the top surface of the ridge stripe 111, and SiO₂To form a dielectric film 113 for current constriction. Further, the second p-GaN contact layer 119 is grown to a thickness of 0.2 μm by the MOCVD method, and the p electrode 115 is formed on the second p-GaN contact layer 119. After that, the obtained wafer may be pseudo-cleavage to form a resonator end face, and the element chip may be divided by dicing.

【0055】

The third difference between the third embodiment and the first and second embodiments is that the resonator length of the laser is set to 550 μm.

【0056】

The kink level of the GaN-based laser device 300 configured as described above is the same as in the case of the first embodiment, and the yield of the device in which kink does not occur up to 40 mW is about 80% or more as in the case of the first embodiment. Become. Further, also in the third embodiment, since the narrow portion of the window portion for current injection exists on the light emitting end face, the same effect as that of the second embodiment can be obtained. As in the case of the second embodiment, in the third embodiment, the narrow portions of the current injection window portion are provided at two locations, the laser light emitting side and the reflecting side, but may be further provided at a plurality of locations. , May be provided only on the exit surface side.

【0057】

(Embodiment 4) FIGS. 7, 8, and 9 are similar to FIGS. 1, 2, and 3, respectively, but schematically illustrate the GaN-based laser device 400 according to the fourth embodiment. ..

【0058】

The first difference between the fourth embodiment and the first, second, and third embodiments is that an n-type conductive GaN substrate 201 having a (0001) plane as a main surface is used as a substrate for a GaN-based semiconductor laser. That is what has been done. Furthermore, the buffer layer is also omitted.

【0059】

The second difference between the fourth embodiment and the first, second, and third embodiments is that the n electrode 117 is formed on the back surface of the n-GaN substrate 201. The n-electrode 117 may be formed after the p-electrode 115 is formed and the total thickness of the wafer is adjusted to 50 to 160 μm. As a result, as can be seen from FIG. 7, the current required for the laser operation is injected from the front surface side and the back surface side of the laser element.

【0060】

The third difference between the fourth embodiment and the first, second, and third embodiments is that the ridge stripe 111 is formed with a width W0 = 3 μm, and the current injection window 114 has a wide portion width W1 = 2.2 μm. It is formed with a narrow width W2 = 1.8 μm.

【0061】

The fourth difference between the fourth embodiment and the first, second, and third embodiments is that the length L1 of the narrow portion of the current injection window 114 is 20 μm, and the length of the transition portion from the wide portion to the narrow portion. The L2 is set to 80 μm. Also in the fourth embodiment, the position where the narrow portion of the current injection window 114 is provided is the same as in the second embodiment.

【0062】

The fifth point that Embodiment 4 differs from Embodiments 1, 2, and 3 is that the resonator formed by cleavage has a length of 500 μm.

【0063】

In the GaN-based laser device of the fourth embodiment as described above, the same horizontal and transverse mode oscillation as in the first embodiment can be obtained. Further, since the current injection window 114 is provided on the ridge stripe 111 and the n-GaN substrate 201 is used, the kink level is compared with the conventional one because the current path is symmetrical with respect to the lateral direction of the ridge stripe. It is possible to increase the yield by about 15 mW, and the yield of the laser that does not generate kink up to an output of 40 mW can be further increased as compared with the case of the first embodiment. With respect to the threshold voltage of the GaN-based laser of the fourth embodiment, the same effect as that of the first embodiment can be obtained. Further, with respect to the horizontal far field pattern (FFP) of the emitted laser light, the same effect as that of the second embodiment can be obtained.

【0064】

(Embodiment 5) FIG. 10 is similar to FIG. 2, but schematically illustrates the GaN-based semiconductor laser 600 according to the fifth embodiment. Note that FIGS. 1 and 3 can be referred to as perspective views and cross-sectional views of the GaN-based laser device 600, respectively. However, in that case, the reference numeral 101 in FIGS. 1 and 3 should be read as 401.

【0065】

The first difference between the fifth embodiment and the first, second, third, and fourth embodiments is that the main surface of the (0001) plane and the sapphire substrate 401 having a thickness of 400 μm are used. .. Along with this, the longitudinal direction of the ridge stripe 111 is formed parallel to the <11-20> direction or the <1-100> direction of the sapphire substrate.

【0066】

The second difference between Embodiment 5 and Embodiments 1, 2, 3, and 4 is that the ridge stripe 111 is formed with a width W0 = 2.0 μm, and the current injection window 114 has a wide portion width W1 =. It is formed with a width of 2.0 μm and a narrow part W2 = 1.5 μm.

【0067】

The third difference between the fifth embodiment and the first, second, third, and fourth embodiments is that the length L1 of the narrow portion of the current injection window 114 is 80 μm, and the transition portion from the wide portion to the narrow portion. The length L2 of is set to 20 μm, and the number of narrow parts is set to 2.

【0068】

The fourth difference between the fifth embodiment and the first, second, third, and fourth embodiments is that the method for manufacturing the laser element is different. First, when forming the p-electrode portion, a first resist having a wide portion width W1 = 2.0 μm and a narrow portion width W2 = 1.5 μm along the <1-100> or <11-20> direction of the sapphire substrate. Form a pattern and SiO₂To form a dielectric film 113 for current constriction. After that, a second resist pattern having a uniform width of 2.0 μm is aligned and formed so as to overlap the first resist pattern, and after removing a predetermined portion of the dielectric film 113 by acid treatment, dry etching is performed. A ridge stripe portion 111 having a width of 2 μm is formed. Subsequently, after re-depositing the dielectric film 113 to prevent current leakage, the first and second resists covering the ridge stripe 111 are removed to form the p electrode 115. The production method not mentioned other than the above is the same as in the case of the first embodiment.

【0069】

In the GaN-based laser element 600 of the fifth embodiment as described above, the same horizontal and transverse mode oscillation as in the first embodiment can be obtained. Further, the kink level of the GaN-based laser element 600 is the same as in the case of the first embodiment, and the yield of the element in which the kink does not occur up to 40 mW is about 80% or more as in the case of the first embodiment. Further, the threshold voltage of the element of the fifth embodiment is also the same as that of the first embodiment.

【0070】

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, in the above-described embodiment, the ridge stripe structure and the embedded hetero (BH) structure have been described as the optical waveguide structure of the semiconductor laser device, but the self-aligned structure (SAS) structure and the channeled subsystem planar (CSP) have been described. ) It will be apparent to those skilled in the art that the present invention can be applied to a laser device having a structure or the like.

【0071】

Further, in the above-described embodiment, a GaN substrate, an n-type GaN substrate, and a sapphire substrate have been described as substrates for the GaN-based semiconductor laser element, but a spinel substrate, a SiC substrate, a ZnO substrate, a GaP substrate, or the like may be used. Alternatively, a substrate on which a GaN-based semiconductor base layer is grown on these substrates, or a GaN-based semiconductor thick-film substrate in which a GaN-based semiconductor thick film is grown on these substrates and then the substrate is removed, and further, Ga and N. A GaN-based semiconductor substrate or the like containing elements other than the above may be used.

【0072】

Further, in the above-described embodiment, SiO is used as the dielectric film material.₂Was explained, but TiO₂, Zirconia, Ta₂O₅, Or Al₂O₃Etc., or a conductive semiconductor layer opposite to the conductive GaN-based semiconductor in contact with the dielectric film can be used as a substitute for the dielectric film.

【0073】

Furthermore, it goes without saying that in each of the above-described embodiments, the conductive type of each semiconductor layer forming the laser structure may be reversed.

【0074】

[Effect of the invention]

As described above, according to the present invention, a narrow portion is provided in a part of the current injection path to the active layer without narrowing the width of the striped waveguide of the GaN-based semiconductor laser device and increasing the operating voltage. This makes it possible to stabilize the transverse mode oscillation. Then, it is possible to provide a GaN-based laser element suitable for application to an optical pickup or the like with a high yield.

[Simple explanation of drawings]

[Figure 1]

It is a schematic perspective view of the GaN-based semiconductor laser device according to Embodiment 1 of this invention.

[Figure 2]

It is a schematic plan view corresponding to the GaN-based semiconductor laser device of FIG.

[Fig. 3]

It is a schematic cross-sectional view corresponding to the GaN-based semiconductor laser device of FIG.

[Fig. 4]

It is a schematic plan view of the GaN-based semiconductor laser device according to the second embodiment of the present invention.

[Fig. 5]

It is a schematic plan view of the GaN-based semiconductor laser device according to the third embodiment of the present invention.

[Fig. 6]

It is a schematic cross-sectional view corresponding to the GaN-based semiconductor laser device of FIG.

[Fig. 7]

It is a schematic perspective view of the GaN-based semiconductor laser device according to Embodiment 4 of this invention.

[Fig. 8]

It is a schematic plan view corresponding to the GaN-based semiconductor laser device of FIG.

[Fig. 9]

It is a schematic cross-sectional view corresponding to the GaN-based semiconductor laser device of FIG.

[Fig. 10]

It is a schematic plan view of the GaN-based semiconductor laser device according to the fifth embodiment of the present invention.

[Fig. 11]

It is a schematic perspective view of the GaN-based semiconductor laser device based on the prior art.

[Explanation of symbols]

100, 200, 300, 400, 500, 600 GaN-based semiconductor laser element, 101 GaN substrate, 201 n-GaN substrate, 401, 501 sapphire substrate, 102, 502 n-GaN buffer layer, 103, 503 n-GaN contact layer , 104, 504 n-AlGaN clad layer, 105, 505 n-GaN guide layer, 106, 506 InGaN multi-quantum well active layer, 107, 507 p-AlGaN anti-evaporation layer, 108, 508 p-GaN optical guide layer, 109, 509 p-AlGaN clad layer, 110, 510 p-GaN contact layer, 111, 511 ridge stripe, 113, 513 dielectric film, 114 window, 115, 515 p electrode, 116 mesa, 117, 517 n electrode, 118 embedded Layer, 119 Second p-GaN contact layer.