Semiconductor light-emitting device and manufacturing method thereof

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a semiconductor light emitting device such as an LED (Light Emitting Diode) or an LD (Laser Diode), and particularly relates to a semiconductor light emitting device having a roughened light extraction surface and a method for manufacturing the same.

【0002】

[Conventional technology]

Conventionally, a high-brightness LED is configured by forming a light emitting portion having a double heterostructure or the like on a semiconductor substrate and forming a current diffusion layer on the light emitting portion. Therefore, when a high-brightness LED is packaged with resin, the upper part of the current diffusion layer has a structure covered with a transparent resin for element protection.

【0003】

In such a structure, the critical angle between the current diffusion layer (refractive index: 3.1 to 3.5) and the transparent resin (refractive index: about 1.5) is 25 to 29 degrees. Of the light directed from the light emitting portion to the transparent resin side, the light whose incident angle with respect to the interface between the current diffusion layer and the transparent resin is larger than the above critical angle is totally reflected. Due to this effect, the probability that the light generated inside the LED is emitted to the outside is significantly reduced. At present, the probability that the light generated inside the LED is emitted to the outside (light extraction efficiency) is about 20%.

【0004】

There is also a method of improving the light extraction efficiency by forming a high refractive index film on the upper part of the current diffusion layer and increasing the critical angle. However, even if this method was used, the efficiency improvement was as low as about 20%.

【0005】

[Problems to be Solved by the Invention]

In this way, in conventional LEDs packaged with transparent resin, most of the light incident on the interface from an oblique direction is totally reflected at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. However, there is a problem that the light extraction efficiency is lowered. Moreover, this problem is not limited to LEDs, and the same can be said for surface-emitting LDs.

【0006】

The present invention has been made in consideration of the above circumstances, and an object of the present invention is the light extraction efficiency due to the influence of total internal reflection of light at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. It is an object of the present invention to provide a semiconductor light emitting device and a method for manufacturing the same, which can prevent the decrease in light intensity and improve the light extraction efficiency.

【0007】

[Means for solving problems]

(Structure) In order to solve the above problems, the present invention adopts the following configuration.

【0008】

That is, the present invention is provided on a substrate having a main surface, a semiconductor multilayer film including a light emitting layer formed on the main surface of the substrate, and a light extraction surface side of the semiconductor multilayer film on the opposite side of the substrate. A surface-emitting semiconductor light emitting device including a plurality of cone-shaped protrusions, and the intersection angle between the bottom surface and the side surface of the plurality of protrusions is set to 30 degrees or more and 70 degrees or less. It is characterized by being done.

【0009】

Further, the present invention is a semiconductor light emitting element including a substrate having a main surface and a semiconductor multilayer film including a light emitting layer formed on the main surface of the substrate, and the substrate of the semiconductor multilayer film. The light extraction surface on the opposite side of the surface is roughened so as to have a large number of uneven shapes, and the distance (height of the unevenness) between the top and bottom of each unevenness on the roughened surface is 50 nm or more. The present invention is characterized in that the wavelength is set to be equal to or lower than the emission wavelength of the light emitting layer, and the present invention includes a substrate having a main surface, a semiconductor multilayer film including a light emitting layer formed on the main surface of the substrate, and the above. A semiconductor light emitting element comprising an antireflection film provided on the light extraction surface side of the semiconductor multilayer film opposite to the substrate and roughened so that the surface has a plurality of uneven shapes. The distance (height of the unevenness) between the top and the bottom of each unevenness of the antireflection film is set to 50 nm or more and equal to or less than the emission wavelength of the light emitting layer.

【0010】

Further, the present invention partially comprises a substrate having a main surface, a semiconductor multilayer film including a light emitting layer formed on the main surface of the substrate, and a light extraction surface side of the semiconductor multilayer film opposite to the substrate. An antireflection film provided on the side of the semiconductor multilayer film on the light extraction surface side of the semiconductor multilayer film except for the first electrode and roughened so that the surface has a large number of uneven shapes. A semiconductor light emitting element including a second electrode formed on the entire back surface side of the substrate, and the distance (height of the unevenness) between the top and the bottom of the unevenness of the antireflection film is It is characterized in that it is set to 50 nm or more and equal to or less than the emission wavelength in the light emitting layer.

【0011】

Further, the present invention comprises a first conductive type compound semiconductor substrate, a double electrode structure portion formed by forming a first conductive type clad layer, an active layer, and a second conductive type clad layer on the substrate. A second conductive type current diffusion layer formed on the second conductive type clad layer of the double electrode structure portion, a second conductive type contact layer formed on the current diffusion layer, and the contact layer. It is provided with an upper electrode selectively formed on the surface, a lower electrode formed on the back surface side of the substrate, and an antireflection film formed on a portion of the contact layer where the electrode is not formed. In a semiconductor light emitting element, the surface of the antireflection film is roughened into a shape having a large number of irregularities, and the distance (height of the irregularities) between the top and bottom of the irregularities due to the rough surface processing is 50 nm or more. It is characterized in that it is set to be equal to or lower than the emission wavelength of the light emitting layer.

【0012】

(Action) According to the present invention, by providing a plurality of cone-shaped protrusions on the light extraction surface side of the semiconductor multilayer film, incident light is incident at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. Can reduce the probability of total internal reflection. Then, by setting the intersection angle between the bottom surface and the side surface of the protrusion to be larger than 30 degrees, it is possible to significantly improve the light extraction efficiency.

【0013】

Here, the above-mentioned value of the crossing angle of 30 degrees was found by the diligent studies and experiments of the present inventors, and when the crossing angle is smaller than 30 degrees, the effect of improving the light extraction efficiency is not so much recognized. When the crossing angle was 30 degrees or more, the light extraction efficiency was improved by 10% or more. In addition, if the crossing angle exceeds 70 degrees, the light extraction efficiency will decrease and the production will become difficult. Therefore, by setting the intersection angle between the bottom surface and the side surface of the protrusion to 70 degrees or less at 30 degrees or more, instead of simply roughening the light extraction surface, it is possible to realize a significant improvement in light extraction efficiency. Become.

【0014】

Further, according to the present invention, by providing an antireflection film having a roughly formed surface on the light extraction surface side of the semiconductor multilayer film, all the incident light is emitted at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. The probability of reflection can be reduced. Then, by setting the surface roughness of the antireflection film to 50 nm or more, more preferably 200 nm or more and an emission wavelength or less, the light extraction efficiency can be significantly improved. Further, by setting the refractive index of the antireflection film between the transparent resin used when packaging this element and the uppermost layer of the semiconductor multilayer film, the effect of improving the light extraction efficiency can be further enhanced.

【0015】

Here, in the conventional structure, the refractive index of the semiconductor multilayer film is about 3.5, whereas the refractive index of the transparent resin for resin encapsulation is about 1.5, and there is a large difference in refractive index. In this case, the critical angle of total reflection in the light from the semiconductor multilayer film side to the transparent resin side becomes small. In the present invention, the critical angle of total reflection can be increased by forming an antireflection film having a refractive index intermediate between the semiconductor multilayer film and the transparent resin (refractive index is 1.5 to 3.5). This makes it possible to improve the light extraction efficiency. Moreover, by roughening the surface of the antireflection film, it is possible to further improve the light extraction efficiency.

【0016】

BEST MODE FOR CARRYING OUT THE INVENTION

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

【0017】

(First Embodiment) FIGS. 1 (a) to 1 (c) are cross-sectional views showing an element structure and a manufacturing process of a green LED according to the first embodiment of the present invention.

【0018】

First, as shown in FIG. 1 (a), AsH is used as a raw material gas for group V elements on an n-type GaAs substrate 10 having a thickness of 250 μm.₃The n-type GaAs buffer layer 11 having a thickness of 0.5 μm is grown by the MOCVD method using the above. After that, PH was used as a raw material gas for group V elements.₃By the MOCVD method using₃Partial pressure is 200Pa, total pressure is 5x10³Under the condition of Pa, n-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 12 and 1.0 μm thick non-doped In_0.5(Ga_0.55Al_0.45)_0.5The P active layer 13 is sequentially grown.

【0019】

Then, PH₃The partial pressure is reduced to 10Pa and the total pressure is 5 × 10.³1.0 μm thick p-type In by MOCVD method without changing Pa_0.5Al_0.5Grow the P-clad layer 14. After that, AsH was used as a raw material gas for group V elements.₃A p-type GaAs contact layer 16 having a thickness of 0.1 μm is grown by the MOCVD method using the above. Here, each epitaxial layer from the buffer layer 11 to the contact layer 16 grows continuously in the same chamber.

【0020】

When growing the p-type InAlP clad layer 14 as described above, PH in the MOCVD method₃When the partial pressure is set sufficiently low (20 Pa or less), the surface of the epitaxial growth film becomes rough. Specifically, as shown in FIG. 2, a cone-shaped protrusion 20 is formed on the growth surface of the InAlP clad layer 14. Then, the angle of the protrusion 20 with respect to the substrate surface, that is, the intersection angle α between the bottom surface and the side surface of the protrusion 20 is larger than 30 degrees.

【0021】

Here, PH during growth of InAlP clad layer 14₃When the partial pressure exceeds 20 Pa, the surface roughness of the clad layer 14 is reduced, and there is a high possibility that the crossing angle of 30 degrees or more at the protrusions cannot be realized. On the other hand, PH₃When the partial pressure is lower than 1 Pa, the surface roughness of the clad layer 14 becomes too large, and the crystallinity of the clad layer 14 also deteriorates. Therefore, the PH during growth of the InAlP clad layer 14₃The desirable range of voltage division was 1 to 20 Pa.

【0022】

Next, as shown in FIG. 1 (b), an ITO film 17 as a transparent electrode is formed on a part of the GaAs contact layer 16 by a sputtering method. Subsequently, a p-side electrode (Au containing Zn) 23 is formed on the ITO film 17. More specifically, after the current block layer 21 and the GaAs layer 22 are grown on the ITO film 17, they are selectively etched so that they remain in the center of the chip. Then, after forming the AuZn electrode 23 on the entire surface, the electrode 23 is patterned so as to remain on the GaAs layer 22 and a part on the ITO film 17.

【0023】

FIG. 3 is a plan view showing an example of the pattern of the p-side electrode 23. This electrode pattern has a circular pad portion 23a provided in the center of the element for adhering a bonding wire or the like, a peripheral portion 23b provided in the peripheral portion of the element, and a connecting portion connecting the pad portion 23a and the peripheral portion 23b. It consists of 23c.

【0024】

Next, as shown in FIG. 1 (c), the back surface of the GaAs substrate 10 is polished to a thickness of 100 μm, and then the n-side electrode 25 (Au containing Ge) is formed on the back surface of the substrate. Then, a heat treatment step of 450 ° C. for 15 minutes is performed in an Ar atmosphere. Subsequently, the substrate 10 on which the layers 11 to 22 and the electrodes 23 and 25 are formed is scribed into chips. Then, for each chip, the resin package is assembled so that the light extraction surface side is covered with a transparent resin (not shown).

【0025】

Although only one chip portion is shown in FIG. 1, a plurality of the constituent portions of FIG. 1 are actually formed on one substrate 10 in order to form a plurality of chips at the same time. Then, by scribe the substrate 10 at the final stage, the substrate 10 is separated into a plurality of chips.

【0026】

Thus, according to the present embodiment, PH occurs when the p-type InAlP clad layer 14 grows.₃By setting the partial pressure lower than usual, a cone-shaped protrusion 20 can be formed on the surface of the clad layer 14. By forming the protrusions 20, it is possible to reduce the probability that the incident light is totally reflected at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. In particular, the PH during growth of the InAlP clad layer 14₃By setting the partial pressure to 1 to 20 Pa, the angle α of the surface cone can be set to 30 degrees or more.

【0027】

Here, FIG. 4 shows the relationship between the angle α formed by the surface of the substrate of the protrusion 20 and the resin incident probability (light extraction efficiency). In FIG. 4, the horizontal axis shows the angle and the vertical axis shows the light extraction efficiency. The light extraction efficiency is 1 when the surface is flat without the protrusion 20. When the angle α was 30 degrees or more, an improvement of 10% or more was observed. On the contrary, when the angle α became too large, the efficiency decreased, and when it exceeded 70 degrees, it became 10% or less. Therefore, the desirable range of the angle α is 30 degrees or more and 70 degrees or less.

【0028】

By adopting the protrusion structure as in this embodiment, as shown in FIG. 4, the light extraction efficiency has been improved to 1.15 times that of the conventional one. In this way, it is extremely effective for LEDs to be able to increase the light extraction efficiency without changing the basic device structure.

【0029】

When the angle α formed by the protrusion 20 with the substrate surface is set to 30 degrees or more, not all the protrusions need to satisfy this, and most (for example, 90% or more) satisfy this. Just do it. By the way, even if you try to make all the protrusions so that the angle α is 30 degrees or more and 70 degrees or less, some parts where the angle α is smaller than 30 degrees or more than 70 degrees may appear. , There is no problem if the ratio of this part is sufficiently low.

【0030】

As described above, in the present embodiment, the light extraction efficiency is not simply roughened, but the intersection angle α between the bottom surface and the side surface of the protrusion 20 is set to 30 degrees or more and 70 degrees or less. Will be able to achieve a significant improvement in.

【0031】

If the period of the protrusion 20 formed on the light extraction surface side becomes extremely small, the effect of improving the light extraction efficiency decreases. According to the experiments by the present inventors, a sufficient effect was observed when the period of the protrusion 20 of the protrusion was 0.5 μm or more. Further, the current block layer 21 and the GaAs layer 22 on the transparent electrode 20 are not always necessary, and the same effect has been confirmed even if the metal electrode 23 is formed directly on the transparent electrode 20.

【0032】

(Second Embodiment) FIG. 5 is a cross-sectional view showing an element structure of a green LED according to a second embodiment of the present invention.

【0033】

In this embodiment, the growth layers of n and p are reversed from those in the first embodiment, and the basic configuration and manufacturing method are the same as those in the first embodiment.

【0034】

0.5 μm thick p-type GaAs buffer layer 31,0.6 μm thick p-type In on p-type GaAs substrate 30_0.5Al_0.5P-clad layer 32,1.0 μm thick non-doped InGaAlP active layer 33,1.0 μm thick n-type In_0.5Al_0.5The P-clad layer 34 and the 0.1 μm-thick n-type GaAs contact layer 36 are grown by the MOCVD method, and the ITO film 37 of the transparent electrode is formed on the P-clad layer 34 by sputtering.

【0035】

Here, as in the first embodiment, when the n-type InAlP clad layer 34 is grown, PH in the MOCVD method is used.₃Make the partial pressure sufficiently low (20 Pa or less). As a result, a cone-shaped protrusion is formed on the surface of the n-type InAlP clad layer 34 as in the first embodiment, and the angle α of this protrusion with respect to the substrate surface becomes larger than 30 degrees.

【0036】

Further, the current block layer 41 and the GaAs layer 42 are selectively formed on the ITO film 37, and the n-side electrode 43 made of AuGe is formed on the GaAs layer 42 and a part of the ITO film 37. Then, a p-side electrode 45 made of ZnAu is formed on the back surface of the GaAs substrate 30.

【0037】

Even with such a configuration, the cone-shaped protrusions provided on the surface of the n-type InAlP clad layer 34 can increase the probability of light incident on the transparent resin for packaging, and the first embodiment The same effect as is obtained.

【0038】

(Third Embodiment) FIGS. 6 (a) and 6 (b) are cross-sectional views showing an element structure and a manufacturing process of a green LED according to a third embodiment of the present invention.

【0039】

First, as shown in FIG. 6A, a 0.6 μm-thick n-type In was placed on an n-type GaAs substrate 50 having a thickness of 250 μm by the MOCVD method._0.5Al_0.5P-clad layer 52, 1.0 μm thick non-doped In_0.5(Ga_0.55Al_0.45)_0.5P active layer 53, 1.0 μm thick p-type In_0.5Al_0.5The P-clad layer 54, the 3.0 μm-thick n-type InGaP current diffusion layer 55, and the 0.1 μm-thick p-GaAs contact layer 56 are grown in the above order. For these epitaxial growth, the MOCVD method was used as in the first embodiment.

【0040】

Next, by introducing a new annealing step (temperature equal to or higher than the epitaxial temperature (600 ° C or higher)) for changing the epitaxial surface shape, the surface of the current diffusion layer 55 is roughened to form protrusions. .. After that, the p-side electrode 63 is formed on the current diffusion layer 55, and the n-side electrode 65 is further formed on the back surface of the substrate 50, and then the exposed p-GaAs layer 56 is removed to show FIG. 6 (b). The structure shown is realized.

【0041】

Here, the surface roughness in the above annealing step will be described in more detail. As the gas used in the annealing step, an inert gas such as hydrogen and a group V gas (for example, AsH) different from the group V element (for example, P) constituting the epitaxial film (group III-V compound, for example, InGaAlP)₃) Is introduced. Then, the group V element (P) of the epitaxial surface layer is re-evaporated. Further, as the next step, an epitaxial step (film type: transparent film (for example, GaP)) is introduced on the rough surface.

【0042】

As a result, as shown in FIG. 7, P is removed from the surface of the InGaP current diffusion layer 55, resulting in a rough surface. Then, a transparent GaP layer 58 is grown on this rough InGaP57. The target surface shape is a structure in which a plurality of convex cones are connected from the mirror surface (Rmax = 5 nm) state, which is the shape of the conventional epitaxial surface, as a structure for improving the luminous efficiency. Here, the intersection angle between the bottom surface and the vertical cross section is an angle larger than 30 degrees.

【0043】

Even with such a configuration, the conical protrusions provided on the surface of the current diffusion layer 55 on the light extraction side can increase the resin incident probability of light, and have the same effect as that of the first embodiment. Is obtained.

【0044】

The p-GaAs contact layer 56 does not have to be removed except for the electrode portion, but it is desirable to remove the p-GaAs contact layer 56 when it absorbs light having an emission wavelength.

【0045】

(Fourth Embodiment) FIG. 8 is a cross-sectional view showing an element structure of a surface emitting LD according to a fourth embodiment of the present invention.

【0046】

First, a 0.5 μm-thick n-type GaAs buffer layer 71 is grown on a 250 μm-thick n-type GaAs substrate 70, and n-In is formed on the n-type GaAs buffer layer 71._0.5Al_0.5A DBR reflective layer 78 having a laminated structure of P / n-GaAs is grown. Subsequently, an n-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 72, non-doped In_0.5(Ga_0.55Al_0.45)_0.5P / In_0.5Ga_0.5MQW active layer 73 of P, and p-type In with a thickness of 0.6 μm_0.5Al_0.5The P-clad layer 74 is grown to form a double heterostructure. Then, p-In_0.5Al_0.5After growing the DBR reflective layer 79 having a laminated structure of P / p-GaAs, p-type In with a thickness of 1.0 μm_0.5Al_0.5A P-current diffusion layer 76 and a 0.1 μm-thick p-type GaAs contact layer 77 are grown.

【0047】

Here, the epitaxial films from the buffer layer 71 to the contact layer 77 grow continuously in the same chamber by using the MOCVD method, and the type and pressure of the gas used are conditions under which each layer grows satisfactorily. However, when forming the current diffusion layer 76, PH is the same as in the first embodiment.₃The partial pressure is sufficiently reduced (eg 10 Pa) so that the growth surface is rough.

【0048】

Next, after forming a resist pattern on the contact layer 77, the laser ridge is formed by etching the resist pattern to the n-type clad layer 72 with a mask. Subsequently, after forming the insulating film 81 so as to remove the upper surface of the ridge, the p-side electrode (Au containing Zn) is vapor-deposited. Then, the upper electrode 83 is formed by removing the portion of the p-side electrode located at the center of the ridge using a resist mask and further removing the p-GaAs contact layer 77. Subsequently, after polishing the GaAs substrate 70 to a thickness of 100 μm, an n-side electrode (Au containing Ge) 85 is formed. Next, heat treatment is performed at 450 ° C. for 15 minutes in an Ar atmosphere. Subsequently, the substrate 70 is scribed to form a chip. After that, the resin package is assembled.

【0049】

In the present embodiment configured in this way, PH occurs when the p-type current diffusion layer 76 grows.₃By reducing the partial pressure, unevenness can be formed on the surface of the p-type current diffusion layer 76, and the angle of the surface cone can be made larger than 30 degrees. Therefore, as in the first embodiment, it is possible to improve the light extraction efficiency. The laser of this embodiment emits red light, but the above effect has been confirmed for semiconductor lasers other than red.

【0050】

The p-GaAs contact layer 77 does not have to be removed, but it is preferable to remove it when it absorbs light having an emission wavelength.

【0051】

(Fifth Embodiment) FIGS. 9 (a) to 9 (c) are cross-sectional views showing an element structure and a manufacturing process of a green LED according to a fifth embodiment of the present invention.

【0052】

First, as shown in FIG. 9A, AsH is used as a raw material gas for group V elements on an n-type GaAs substrate 110 having a thickness of 250 μm.₃An n-type GaAs buffer layer 111 having a thickness of 0.5 μm is grown by the MOCVD method using. Subsequently, PH is used as a raw material gas for III-element elements.₃By the MOCVD method using₃Partial pressure is 200Pa, total pressure is 5x10³Under the condition of Pa, n-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 112, 1.0 μm thick non-doped InGaAlP active layer 113, 1.0 μm thick p-type In_0.5Al_0.5The P-clad layer 114 and the 1.0 μm-thick p-type InGaP current diffusion layer 115 are sequentially grown. After that, AsH was used as a raw material gas for group V elements.₃A 0.1 μm-thick p-type GaAs contact layer 116 is grown by the MOCVD method using. Here, each epitaxial layer from the buffer layer 111 to the contact layer 116 grows in the same batch.

【0053】

Next, as shown in FIG. 9B, the antireflection film 117, which is a feature of the present embodiment, is formed. That is, TiO on the polyimide resin₂The antireflection film 117 having a refractive index of 2.0 formed by adding the above is formed on the contact layer 116 by spin coating, and then the surface of the antireflection film 117 is pressed with a mold having irregularities equal to or lower than the emission wavelength. Shape it. As a result, the surface roughness (PV value (max-min)) of the antireflection film 117 is set to be equal to or lower than the emission wavelength. Here, the PV value is the distance (height) between the peak and the valley at each unevenness.

【0054】

Next, a resist mask (not shown) is formed on the antireflection film 117, the antireflection film 117 of the electrode forming portion is removed by RIE, and then the resist mask is removed. Subsequently, as shown in FIG. 9 (c), an electrode material (Au containing Zn) is vapor-deposited on the antireflection film 117 and the exposed contact layer 116, and then patterning is performed using a resist mask (not shown). As a result, the upper electrode (p-side electrode) 118 is formed. The pattern of the p-side electrode 118 is the same as that shown in FIG.

【0055】

Next, the back surface of the GaAs substrate 110 is polished to a thickness of 100 μm, and then the lower electrode 119 (Au containing Ge) to be the n-side electrode is formed. Then, a heat treatment step of 450 ° C. for 15 minutes is performed in an Ar atmosphere. Subsequently, the substrate 110 is scribed to form a chip. Then, after the assembly wire bonding, the resin is sealed with an epoxy resin (n = about 1.5).

【0056】

As described above, according to the present embodiment, by roughening the surface of the antireflection film 117, the light extraction efficiency is improved from about 20% in the conventional case to about 30%. That is, the light extraction efficiency has been improved to 1.5 times that of the conventional one. It is extremely effective for LEDs to be able to increase the light extraction efficiency by this amount without changing the basic device structure.

【0057】

FIG. 10 is a diagram showing the relationship between the PV value and the light extraction efficiency. As the PV value increases, the extraction efficiency improves. When the PV value is 50 nm, the light extraction efficiency is about 1.5 times, and when the PV value is 200 nm or more, the light extraction efficiency is about 2 times, which is almost constant. FIG. 11 is a diagram showing the relationship between the PV value and the light extraction efficiency before and after the emission wavelength. Sufficient light extraction efficiency is obtained when the wavelength is shorter than that of the emission wavelength of 640 nm, but when the wavelength is higher than that, the light extraction efficiency decreases sharply. Therefore, the desired range of PV values is 50 nm or more (more preferably 200 nm or more) and shorter than the emission wavelength.

【0058】

When the PV value is 50 nm or more (more preferably 200 nm or more) and the emission wavelength or less, it is not always necessary to satisfy this for all irregularities, and it is sufficient to satisfy this for most (for example, 90% or more). .. That is, even if an attempt is made to form the wavelength at 200 nm PV emission wavelength, unevenness that deviates from this may appear in some parts, but if this is a sufficiently low ratio, there is no problem.

【0059】

FIG. 12 is a diagram showing the relationship between the refractive index and the light extraction efficiency when the surface of the antireflection film is roughened as in the present embodiment. This indicates the ratio of light output from the other surface of the antireflection film when light is incident on one main surface of the antireflection film at an incident angle of -90 degrees to +90 degrees. Based on a refractive index of 1.5 (same as the underlying semiconductor layer), the light extraction efficiency increases by about 50% when the refractive index is 2.0 (this embodiment), and increases by about 100% when the refractive index is 2.5. I understand.

【0060】

FIG. 13 is a diagram showing the relationship between the refractive index and the light extraction efficiency when the surface of the antireflection film is flat. In this case, when the refractive index is 2.0, the increase is only 8%, and when the refractive index is 2.5, the increase is only 9%. From this, it can be seen that in order to improve the light extraction efficiency, it is essential not only to increase the refractive index of the antireflection film but also to roughen the surface of the antireflection film.

【0061】

According to the experiments by the present inventors, from the viewpoint of improving the light extraction efficiency, a sufficient effect can be obtained by setting the surface roughness (PV value (max-min)) of the antireflection film to the emission wavelength λ or less. I'm checking. Furthermore, it has been confirmed that a more reliable effect can be obtained by using a conical shape or a polygonal shape (triangular pyramid, quadrangular pyramid, hexagonal pyramid, etc.) having a period of 0.5λ or less as the surface shape of the antireflection film.

【0062】

As described above, according to the present embodiment, by providing the antireflection film having a rough surface on the light extraction surface side of the semiconductor multilayer film, the film is incident at the boundary between the uppermost layer of the semiconductor multilayer film including the light emitting layer and the transparent resin. The probability of total internal reflection of light can be reduced. Then, by setting the surface roughness of the antireflection film to be equal to or lower than the emission wavelength, it is possible to significantly improve the light extraction efficiency. Further, by setting the refractive index of the antireflection film between the transparent resin used when packaging this element and the uppermost layer of the semiconductor multilayer film, the effect of improving the light extraction efficiency can be further enhanced.

【0063】

Here, in the conventional structure, the refractive index of the semiconductor multilayer film is about 3.5, whereas the refractive index of the transparent resin for resin encapsulation is about 1.5, and there is a large difference in refractive index. In this case, the critical angle of total reflection in the light from the semiconductor multilayer film side to the transparent resin side becomes small. In the present embodiment, the critical angle of total reflection can be increased by forming an antireflection film having a refractive index intermediate between the semiconductor multilayer film and the transparent resin (refractive index is 1.5 to 3.5). As a result, the light extraction efficiency can be improved. Moreover, by roughening the surface of the antireflection film, it is possible to further improve the light extraction efficiency.

【0064】

The emission wavelength of the LED is not limited to green, and the above effect has been confirmed for visible light products other than green. Further, it has been confirmed that the shape of the unevenness below the wavelength in the antireflection film improves the light extraction efficiency in any of the structures shown in FIGS. 14 (a) to 14 (e).

【0065】

In addition to InGaAlP, the same effect has been confirmed for InGaAlAs, AlGaAs, and GaP as LED materials. Further, as the material of the antireflection film, acrylic resin and TiO₂, TaO₂, ZrO₂The same effect can be obtained with a mixture of.

【0066】

(Sixth Embodiment) FIG. 15 is a cross-sectional view showing an element structure of a green LED according to a sixth embodiment of the present invention.

【0067】

This embodiment has a structure in which p / n in the fifth embodiment is inverted, and the manufacturing method is substantially the same as that in the fifth embodiment. That is, on a p-type GaAs substrate 120 with a thickness of 250 μm, a p-type GaAs buffer layer 121 with a thickness of 0.5 μm and a p-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 122, 1.0 μm thick non-doped In_0.5(Ga_0.55Al_0.45)_0.5P active layer 123, 1.0 μm thick n-type In_0.5Al_0.5The P-clad layer 124, the 1.0 μm-thick n-type InGaP current diffusion layer 125, and the 0.1 μm-thick n-type GaAs contact layer 126 are grown and formed in the same batch.

【0068】

Then, as in the first embodiment, an antireflection film 127 having a refractive index of 2.0 is formed on the contact layer 126 by spin coating, and the surface thereof is roughened by press shaping with a mold. A part (electrode forming portion) of the antireflection film 127 is removed, and an upper electrode (n-side electrode) 128 is formed on the contact layer 126 exposed in this portion. Further, a lower electrode 129 serving as a p-side electrode is formed on the back surface of the GaAs substrate 120. The configured wafer is chipped by scribe and sealed with resin after assembling wire bonding.

【0069】

Even with such a configuration, the light extraction efficiency is improved to about 2.5 times that of the conventional one, as in the fifth embodiment. Further, it was confirmed that the same effect was obtained in visible light products other than green, and that the light extraction efficiency was further improved in any of the structures shown in FIGS. 14 (a) to 14 (e).

【0070】

(7th Embodiment) FIG. 16 is a cross-sectional view showing an element structure of a surface emitting laser according to a seventh embodiment of the present invention.

【0071】

First, a 0.5 μm-thick n-type GaAs buffer layer 131 is grown on a 250 μm-thick n-type GaAs substrate 130, and then n-In._0.5Al_0.5A multilayer reflective film 132 having a laminated structure of P / n-GaAs was grown. Subsequently, an n-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 133 and non-doped In_0.5(Ga_0.55Al₀_.45) 0.5P / In_0.5Ga_0.5MQW active layer 134 consisting of P and p-type In with a thickness of 0.6 μm_0.5Al_0.5P-clad layer 135 was grown. Then p-In_0.5Al_0.5A multilayer reflective film 136 having a laminated structure of P / p-GaAs was grown. In addition, 1.0 μm thick p-type In_0.5Al_0.5A P-current diffusion layer 137 and a 0.1 μm-thick p-GaAs contact layer 138 were grown. Here, each epitaxial layer from the buffer layer 131 to the contact layer 138 grew in the same batch.

【0072】

Next, a resist mask was formed in stripes on the contact layer 138, and then wet etching was performed from the surface to the n-type clad layer 133 to form a laser ridge. Subsequently, a 0.5 μm thick SiO is used so as to remove the upper surface of the ridge.₂The insulating film 141 was formed. Further, a p-side electrode (Au containing Zn) was vapor-deposited on the contact layer 138 and the insulating film 141, and the upper electrode 142 was formed with a resist mask. Here, the upper electrode 142 comes into contact with the peripheral portion of the upper surface of the contact layer 138, and the central portion of the upper surface of the contact layer 138 is exposed.

【0073】

Next, TiO on the polyimide resin₂An antireflection film 144 having a refractive index of 2.0 is formed by spin coating, and the surface thereof is press-shaped with a mold having irregularities below the wavelength. As a result, the surface roughness (PV value (max-min)) of the antireflection film 144 is set to be equal to or lower than the emission wavelength. Then, the unnecessary portion of the antireflection film 144 is removed.

【0074】

Next, the back surface side of the GaAs substrate 130 is polished to a thickness of 100 μm, and then the n-side electrode (Au containing Ge) 143 is formed. Further, as a heat treatment, the heat treatment is performed at 450 ° C. for 15 minutes in an Ar atmosphere. Then, the wafer is scribed into chips, and then assembled into an epoxy resin (n = about 1.5) package.

【0075】

Even with such a configuration, as in the fifth embodiment, the refractive index is intermediate between the underlying semiconductor layer and the sealing resin, and the antireflection film 144 having a roughened surface is formed. , It is possible to greatly improve the light extraction efficiency. Further, as in the fifth embodiment, it has been confirmed that the surface shape of the antireflection film improves the light extraction efficiency in any of the structures shown in FIGS. 14 (a) to 14 (e). In addition to InGaAlP, similar effects have been confirmed for InGaAlAs, AlGaAs, and GaP semiconductor materials. Further, as the material of the antireflection film, acrylic resin and TiO₂, TaO₂, ZrO₂The same effect can be obtained with a mixture of.

【0076】

(Modified Example) The present invention is not limited to the above-described embodiments. In the first and fourth embodiments, PH during growth is used as a method of roughening the crystal surface.₃I set the partial pressure to 10Pa, but PH₃The partial pressure may be appropriately set in the range of 1 to 20 Pa. Further, in the third embodiment, AsH is used as a method of roughening the crystal surface.₃Was introduced and annealed, but the gas used for this annealing is AsH.₃It is not limited to the above, and any element may contain a group V element different from the group V element constituting the semiconductor layer to be roughened and hydrogen gas. Further, as a method of roughening the crystal surface, the above-mentioned PH at the time of growth is used.₃It is not limited to reducing the partial pressure and annealing after growth, but it is also possible to randomly process the surface of the semiconductor layer with a grinder with a tip angle of 120 degrees or less.

【0077】

Further, the protrusion is not limited to a cone, and may be a pyramid such as a triangular pyramid, a quadrangular pyramid, or a hexagonal weight. The protrusions do not necessarily have to be formed on the entire surface on the light extraction surface side, but it is desirable that the ratio of the occupied area of the protrusions on the light extraction surface side is as large as possible, and a sufficient effect can be obtained if it is 50% or more. Be done.

【0078】

Here, since the light extraction efficiency is proportional to the occupied area, the light extraction effect is halved (1.1 times or less) when the occupied area of the protrusion is 50% or less. Further, when the period of the protrusion is 0.2 to 0.5 μm, the effect of improving light extraction becomes small (1.1 times or less), and when the period is 0.2 μm or less, the graded-index effect occurs.

【0079】

In the fifth to seventh embodiments, a mold having irregularities was used to roughen the antireflection film, but instead, after the antireflection film was formed, the surface was surfaced in a random direction with a grinder. You may try to ruin it. In this case, various materials other than resin-based materials can be used.

【0080】

Further, the provision that the surface roughness (PV value) is 50 nm or more and the emission wavelength or less is not necessarily limited to the antireflection film, and can be applied to other layers as long as it is on the light extraction surface side of the semiconductor multilayer film. Specifically, it can also be applied to a diffusion layer and a contact layer. That is, in the first to fourth embodiments, the surface roughness (PV value) on the uneven surface may be set to the emission wavelength or less. Further, both the regulation that the surface roughness (PV value) is equal to or higher than the emission wavelength and the regulation that α is 30 degrees or higher may be satisfied.

【0081】

Further, if the current can be sufficiently spread from the upper electrode to the active layer other than directly under the upper electrode, the current diffusion layer is not always necessary and can be omitted. Further, conditions such as the material, composition, and thickness of the semiconductor layer constituting the light emitting element can be appropriately changed according to the specifications.

【0082】

Further, in the embodiment, an example of resin-sealing using a transparent resin has been described, but the present invention is not limited to the case of resin-sealing. When not sealed with resin, air comes into direct contact with the antireflection film, but in this case as well, since the difference in refractive index between the semiconductor multilayer film and air is large, the effect of improving the light extraction efficiency by forming the antireflection film is effective. Is obtained as well.

【0083】

In addition, various modifications can be made without departing from the gist of the present invention.

【0084】

[Effect of the invention]

As described in detail above, according to the present invention, a plurality of cone-shaped projections are provided on the light extraction surface side of the semiconductor multilayer film including the light emitting layer, and the intersection angle between the side surface of the projection and the light extraction surface is determined. By setting the temperature to 30 degrees or more and 70 degrees or less, it is possible to prevent the light extraction efficiency from being lowered due to the influence of total reflection at the boundary between the uppermost layer of the semiconductor multilayer film and the transparent resin, and to improve the light extraction efficiency. It can be measured.

【0085】

Further, according to the present invention, an antireflection film is formed on the light extraction surface side of the semiconductor multilayer film including the light emitting layer, and the surface of the antireflection film is roughened to roughen the boundary between the uppermost layer of the semiconductor multilayer film and the transparent resin. It is possible to prevent the light extraction efficiency from being lowered due to the influence of the total reflection of light in the above, and it is possible to improve the light extraction efficiency.

[Simple explanation of drawings]

[Figure 1]

The cross-sectional view which shows the element structure and manufacturing process of the green LED which concerns on 1st Embodiment.

[Figure 2]

FIG. 5 is an enlarged cross-sectional view showing the shape of a protrusion formed on the light extraction surface side of the LED in FIG.

[Fig. 3]

The plan view which shows the example of the electrode pattern in the LED of FIG.

[Fig. 4]

FIG. 5 is a diagram showing the relationship between the angle α formed by the side surface of the protrusion and the surface of the substrate in the LED of FIG. 1 and the light extraction effect.

[Fig. 5]

The cross-sectional view which shows the element structure of the green LED which concerns on 2nd Embodiment.

[Fig. 6]

The cross-sectional view which shows the element structure and manufacturing process of the green LED which concerns on 3rd Embodiment.

[Fig. 7]

FIG. 5 is an enlarged cross-sectional view showing the structure near the light extraction surface in the third embodiment.

[Fig. 8]

The cross-sectional view which shows the element structure of the surface light emitting type LD which concerns on 4th Embodiment.

[Fig. 9]

The cross-sectional view which shows the element structure and manufacturing process of the green LED which concerns on 5th Embodiment.

[Fig. 10]

The characteristic diagram which shows the relationship between the height of unevenness and the light extraction efficiency in the LED of FIG.

[Fig. 11]

A characteristic diagram showing the relationship between the height of unevenness and the light extraction efficiency before and after the emission wavelength.

[Fig. 12]

The figure which shows the relationship between the refractive index and light extraction efficiency when the surface of an antireflection film is roughened.

[Fig. 13]

The figure which shows the relationship between the refractive index and light extraction efficiency when the surface of an antireflection film is flat.

[Fig. 14]

The cross-sectional view which shows the example of the rough surface shape of the antireflection film.

[Fig. 15]

The cross-sectional view which shows the element structure of the green LED which concerns on 6th Embodiment.

[Fig. 16]

The cross-sectional view which shows the element structure of the surface light emitting LD which concerns on 7th Embodiment.

[Explanation of symbols]

10 ... n-type GaAs substrate 11 ... n-type GaAs buffer layer 12 ... n-type InAlP clad layer 13 ... InGaAlP active layer 14 ... p-type InAlP clad layer 16 ... n-type GaAs contact layer 17 ... ITO film 20 ... protrusion 21 ... Current block layer 22 ... GaAs layer 23 ... AuZn electrode (p side electrode) 25 ... AuGe electrode (n side electrode) 110 ... n-type GaAs substrate 111 ... n-type GaAs buffer layer 112 ... n-type InAlP clad layer 113 ... InGaAlP active layer 114 ... p-type InAlP clad layer 115 ... p-type InGaP current diffusion layer 116 ... p-type GaAs contact layer 117 ... Anti-reflective coating 118 ... Upper electrode (p side electrode) 119 ... Lower electrode (n-side electrode) n-side electrode