JP3790677B2 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device using a nitride-based semiconductor material, in particular, a light emitting device using Ga _x In _y Al _z B _1-xyz N (0 ≦ x, y, z, x + y + z ≦ 1) and a method for manufacturing the same. .
[0002]
[Prior art]
In recent years, there has been a growing need for visible semiconductor light emitting devices for light sources such as solid state lighting and liquid crystal projectors. Compared with a lamp light source, the semiconductor light emitting device has various advantages such as high efficiency, low power consumption, long life, brightness, no light source replacement, and compactness. In the case of an RGB3 type liquid crystal projector, if a visible semiconductor laser having a brightness exceeding 1000 lm (lumen) can be realized as a light source, a large screen projection of 100 inches or more can be achieved even in a daylight environment.
[0003]
In the case of a lamp light source liquid crystal projector currently in practical use, out of the luminous flux of 1000 lm of the lamp light source, the projected light utilization efficiency is as low as 3% or less, and the power efficiency of the lamp is also low. For this reason, it will be limited to the use of air-cooling in a dim room. When a semiconductor light emitting device (LED) is used as a light source, the luminous efficiency is about the same as that of a lamp, and the light utilization efficiency is improved to about twice that of the lamp by using a lens system that does not split light. This is a dramatic improvement over lamps, but still has limited use.
[0004]
On the other hand, the use of a semiconductor laser as the light source is expected because it can improve the light emission efficiency, improve the light utilization efficiency associated therewith, and further reduce the power consumption. However, among semiconductor lasers of red (R), green (G), and blue (B) three primary wavelengths (R: 630 nm, G: 520 nm, B: 470 nm) that can represent the most diverse colors on the chromaticity diagram, G and B are realized using second harmonic generation or using ZnSe-based materials, but these have not been put into practical use.
[0005]
In addition, it is theoretically known that a GaN semiconductor laser having a quantum well structure can oscillate any of R, G, and B, and a blue-violet light emitting laser can continuously oscillate at room temperature for several thousand hours or more. It has been realized. However, the oscillation wavelength is 400 to 450 nm, and blue light emission with a shorter wavelength is desired as a light source for high-density recording in liquid crystal projectors and optical disk systems.
In addition, the artificially produced GaN substrate has many crystal defects such as dislocations, which hinders high output and low threshold of GaN semiconductor lasers. Furthermore, due to defects in the GaN substrate, composition fluctuations are large in a multi-component laminated film such as an active layer, which makes the oscillation wavelength controllability low.
[0006]
[Problems to be solved by the invention]
GaN-based materials are expected as a light source for next-generation liquid crystal projectors and optical disk systems, but as described above, due to crystal defects in the GaN substrate, higher output, lower threshold, and oscillation wavelength controllability It is the actual situation that etc. are restricted.
[0007]
An object of the present invention is to provide a semiconductor light-emitting device using a nitride-based semiconductor, which has a low oscillation threshold current, increases output, and improves oscillation wavelength controllability, and a method for manufacturing the same.
[0008]
[Means for Solving the Problems]
The semiconductor light emitting device according to the present invention, the substrate, is formed on the substrate, a step is formed with a substantially vertical sides to the surface, a buffer layer made of a nitride-based semiconductor, the substrate on the side surface of the step A lower cladding layer epitaxially grown with a growth surface inclined with respect to the substrate, and an active layer made of a nitride-based semiconductor epitaxially grown with a growth surface inclined with respect to the substrate only on the inclined growth surface of the lower cladding layer And an upper clad layer that is epitaxially grown to cover the active layer, and a void formed so as to penetrate the upper clad layer and reach the upper surface of the step .
[0009]
The semiconductor light-emitting device according to the present invention also includes a substrate and a first conductivity type first Ga _x In _y Al _z B _1-1 formed on the substrate and having a step having a side surface substantially perpendicular to the surface. _x-y-z N (0 ≦ x, y, z, x + y + z ≦ 1) buffer layer made of a semiconductor, and epitaxial growth is performed with a growth surface inclined with respect to the substrate on the side surface of the step of the buffer layer. A lower clad layer made of a one-conductivity-type second Ga _x In _y Al _z B _1-x-yz N (0 ≦ x, y, z, x + y + z ≦ 1) semiconductor, and an inclination of the lower clad layer A third Ga _x In _y Al _z B _1-xyz N (0 ≦ x, y, z, x + y + z ≦ 1) having a growth surface that is epitaxially grown only on the grown surface and is inclined with respect to the substrate. ) An active layer made of a semiconductor, Fourth _{Ga x In y Al z B 1} -x-y-z N (0 ≦ x, y, z, x + y + z ≦ 1) based upper made of a semiconductor of the second conductivity type over the active layer epitaxially grown It has a clad layer and a gap formed so as to penetrate the upper clad layer and reach the upper surface of the step .
[0010]
The method of manufacturing a semiconductor light emitting device according to the present invention includes a step of epitaxially growing a buffer layer made of a nitride-based semiconductor layer on a substrate, a step of processing a step with a side surface substantially perpendicular to the surface of the buffer layer, and the buffer Epitaxially growing a lower cladding layer with a growth surface inclined with respect to the substrate on the side surface of the step, and a growth surface inclined with respect to the surface of the substrate only on the inclined growth surface of the lower cladding layer A step of epitaxially growing an active layer made of a nitride-based semiconductor, a step of epitaxially growing an upper clad layer covering the active layer, and forming a gap so as to penetrate the upper clad layer and reach the upper surface of the step And a process .
[0011]
According to the present invention, the active layer made of a nitride-based semiconductor is epitaxially grown on the substantially vertical side surface of the step formed on the substrate with a growth surface inclined with respect to the substrate. Thereby, even when a nitride semiconductor such as GaN with many dislocations is used, crystal defects such as threading dislocations propagating from the substrate into the active layer can be effectively avoided. When a large number of semiconductor layers are formed from a substrate under conditions of lattice mismatch, large strain stress is likely to occur. However, in the present invention, the active layer portion is epitaxially grown on the side surface of the step, so that the strain entering the active layer is also suppressed. be able to. As described above, according to the present invention, various effects on the active layer from the substrate can be suppressed, and as a result, the threshold current is low, the output is high, and the oscillation wavelength is highly controllable. A device is obtained.
[0012]
In the present invention, specifically, the step of the buffer layer is a stripe upper protrusion. For example, the protrusion is formed by dry etching the buffer layer. The active layer is formed in a stripe shape along the side surface of the stripe-like projection.
Alternatively, the step of the buffer layer can be a columnar protrusion. Such columnar protrusions are also formed by dry etching the buffer layer. In this case, the active layer is formed with a shape that goes around the columnar protrusion.
[0013]
The semiconductor light emitting device according to the present invention includes, for example, a plurality of active layers formed on a substrate, and can be formed into a chip so that the plurality of active layers are driven in parallel. Alternatively, a plurality of active layers formed on the substrate can be included, and the plurality of active layers can be formed into chips so as to be driven in series.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[Embodiment 1]
1A and 1B show a cross-sectional view and a chip plan view of a GaN-based semiconductor laser according to an embodiment of the present invention. The GaN substrate 10 is n-type GaN (Si-doped: 5 × 10 ¹⁸ / cm ³ , 80 μm) having a (0001) c-axis Ga plane as a main surface. An n-type Al _0.05 Ga _0.95 N buffer layer 11 is epitaxially grown on the GaN substrate 10. The surface of the buffer layer 11 has a step formed by processing the stripe-shaped protrusion 23 by anisotropic dry etching. The step side surface 12 is substantially perpendicular to the substrate surface.
[0015]
A SiO ₂ spacer 13 is formed on the bottom surface (groove portion) of the step. Then, using the side surface 12 of the step as a seed for crystal growth, an n-type Al _0.07 Ga _0.93 N cladding layer (Si-doped: 5 × 10 ¹⁸ / cm ³ ) 14 and an active layer 15 are sequentially epitaxially grown in the lateral direction, and further activated A p-type Al _0.07 Ga _0.93 N clad layer (Mg doped: 5 × 10 ¹⁸ / cm ³ ) 16 is epitaxially grown so as to cover the layer 15. Specifically, the active layer 15 includes an n-type GaN optical waveguide layer (Si-doped: 1 × 10 ¹⁸ / cm ³ , 0.1 μm), In _0.11 Ga _0.89 N well layer (3 nm, 3 layers) / In _0.02 Ga _0.98 SCH-MQW (Separate Confinement Heterostructure) configured as a multi-quantum well layer with an N barrier layer (6 nm) and a p-type GaN optical waveguide layer (Mg doped: 1 × 10 ¹⁸ / cm ³ , 0.1 μm) Multi-Quantum Well) active region with a lateral width of 2 μm.
[0016]
The clad layer 14 is formed with a growth surface of about 60 ° with respect to the surface of the substrate 10 by appropriately selecting the growth conditions and selectively epitaxially growing only on the side surface 12 of the step. In the figure, the clad layer 14 is also formed on the upper surface of the protrusion 23, but this is actually the one that grows laterally from the stepped side surface 12 and projects on the protrusion 23. Then, the active layer 15 is selectively epitaxially grown while maintaining the inclination on the growth surface of the cladding layer 14. Therefore, the active layer 15 is formed with a surface inclined by about θ = 60 ° with respect to the surface of the substrate 10. Even if the InGaN layer of the active layer component grows slightly on the upper surface of the cladding layer 14, it does not function as an active layer by optimizing the film thickness control of the SCH-MQW layer in the lateral direction.
[0017]
A p-type GaN contact layer (Mg doped: 5 × 10 ¹⁸ / cm ³ , 0.1 μm) 17 is epitaxially formed on the p-type AlGaN cladding layer 16. A p-side electrode 18 made of Pt / Au is formed on the p-type contact layer 16, and an n-type electrode 19 made of Ti / Pt / Au is formed on the back surface of the substrate 10. The p-type electrode 18 is connected to the AlN submount chip 21 via the AuSn solder layer 20.
[0018]
The manufacturing process of the semiconductor laser of this embodiment will be specifically described with reference to FIGS. 2A to 2D. First, as shown in FIG. 2A, an AlGaN buffer layer 11 is formed on the mirror-finished GaN substrate 10 by metal organic chemical vapor deposition (MOCVD). Here, the Al composition ratio of the AlGaN buffer layer 11 may be between 0 and the Al composition ratio of the AlGaN cladding layer formed on the AlGaN buffer layer 11, and the Al composition ratio may continuously change during this period. Alternatively, the Al composition ratio of the AlGaN buffer layer 11 may be constant in the film thickness direction, and a buffer layer whose Al composition ratio further changes may be interposed in the base.
[0019]
A SiO ₂ mask or a resist mask (not shown) is formed on the AlGaN buffer layer 11, and the AlGaN buffer layer 11 is etched by anisotropic dry etching, thereby forming stripe-shaped projections 23 at a predetermined interval as shown in FIG. 2A. Form. The stepped side surface 12 of the stripe-like projection 23 becomes a substantially vertical surface, and a spacer 13 such as SiO ₂ or SiN is buried in the bottom of the groove in order to make this a surface for the next crystal growth. However, the stripe-shaped protrusions 23 are not necessarily required, and groove processing may be used to obtain the step 12. When the depth of the groove is deeper than a certain level, the embedding of the spacer 13 can be omitted. As the spacer 13, a diffraction grating for controlling the longitudinal mode of laser oscillation may be formed.
[0020]
Next, as shown in FIG. 2B, the n-type AlGaN cladding layer 14 is epitaxially grown by MOCVD, and then the SCH-MQW active layer 15 is epitaxially grown. At this time, the AlGaN cladding layer 14 suppresses the growth in the vertical direction so that the step side surface 12 of the stripe-like projection 23 is grown mainly in an oblique direction using the seed of crystal growth. For that purpose, it is necessary to optimize the mixing ratio of hydrogen and nitrogen as carrier gas, the partial pressure of ammonia gas, and the growth temperature.
[0021]
For example, when the ratio of the nitrogen gas in the carrier gas is increased, the lateral growth rate is increased, and the main growth surface becomes nearly perpendicular to the surface of the substrate 10. When the ammonia partial pressure is increased, the threading dislocations in the vertical direction from the substrate 10 easily move in the disordered direction in the growth film, the dislocation density decreases with the growth time, and crystal defects such as point defects are hardly formed. When the growth temperature is raised, the main growth surface tends to be perpendicular to the surface of the substrate 10.
[0022]
In consideration of these matters, in this embodiment, the carrier gas mixing ratio is hydrogen: nitrogen = 2: 1, the ammonia partial pressure is 360 Torr (1/2 atm), the growth temperature is 1050 ° C., and the n-type The AlGaN cladding layer 14 and the SCH-MQW active layer 15 were epitaxially grown. Thereby, the clad layer 14 and the active layer 15 were formed with an inclination of about 60 ° with respect to the substrate 10. The clad layer 14 is grown on both sides of the protrusion 23 and is connected on the protrusion 2. The InGaN quantum well layer of the active layer 15 was grown at a growth temperature of 800 ° C. in an atmosphere containing only nitrogen gas. The stripe width of the active layer 15 formed with a slope is about 2.1 μm.
[0023]
Thereafter, as shown in FIG. 2C, a p-type AlGaN cladding layer 16 is epitaxially grown by MOCVD so as to cover the active layer 15 and the cladding layer. The clad layer 16 is grown until the gap between the stripe-shaped protrusions 23 is filled and the growth layers on both sides of the stripe-shaped protrusions 23 are combined, and eventually the surface becomes almost flat. However, some V grooves may remain. Thereafter, as shown in FIG. 2D, the p-type GaN contact layer 17 is epitaxially grown to planarize the surface almost completely.
[0024]
Thereafter, as shown in FIG. 1, the p-side electrode 18 and the solder layer 20 are formed on the GaN contact layer 17. The n-side electrode 19 is formed on the GaN substrate 10 after the back surface is polished and the thickness is adjusted to about 80 μm. Next, the wafer is cleaved with a cleavage plane parallel to the cross section of FIG. 2 so that the resonator length is 0.5 mm. 1B is coated with a highly reflective film by ECR-CVD (electron cyclotron resonance CVD) or sputtering. Specifically, the highly reflective film is a TiO2 / SiO2 film having a quarter wavelength thickness of the laser oscillation wavelength. Furthermore, after cutting in a direction perpendicular to the plane of FIG. 2 to form chips each including the active layer 15, the surface of the solder layer 20 and the AlN mount chip 21 are thermocompression bonded at 320 ° C. .
[0025]
In the semiconductor laser of this embodiment, when a forward bias voltage is applied, the current flowing from the p-side electrode 18 flows laterally through the active layer 15, and further flows downward through the protrusion 23, thereby causing the n-side electrode 19. to go into. The upper and lower cladding layers 16 and 14 are also in direct contact with the outside of the active layer 15 to form a pn junction, but the barrier is higher than the barrier between the p-type cladding layer 16 and the active layer 15, and therefore the active layer. Since the current crossing 15 becomes dominant, laser oscillation becomes possible. Specifically, continuous oscillation at room temperature with an operating voltage of 4.2 V, a threshold current of 30 mA, and an oscillation wavelength of 403 nm was observed. The lifetime of the element by driving at 80 ° C. and 50 W was 5000 hours or more. Further, the far field pattern (FFP) has a single peak at a horizontal angle of 8 ° and a vertical angle of 22 °, and beam characteristics suitable for optical disc application were obtained.
[0026]
In the laser of this embodiment, the active layer is not grown perpendicularly to the substrate surface, but is grown laterally on the side surface of the stripe-shaped protrusion. Therefore, the active layer has a low dislocation density without being affected by threading dislocations from the substrate, thereby reducing the leakage current. Further, since the MQW layer at the center of the active layer 15 is formed on the surface of the GaN optical waveguide layer having a flat Ga surface, oscillation with a low threshold current is possible. Furthermore, since the n-type AlGaN cladding layer 14 is formed on the side surface of the stripe-shaped protrusion 23, it is not affected by the lattice constant of the GaN substrate 10 and becomes a layer close to the original lattice constant, which is free standing, and is free from distortion and dislocation. There are few and it is hard to produce a crack etc. For this reason, by thickening the n-type AlGaN cladding layer 14 to some extent, the light confinement effect can be made sufficient, which leads to a reduction in the oscillation threshold value.
[0027]
In order to reduce the operating current, it is also effective to adopt an AlGaN / GaN superlattice structure for the cladding layer. The heat generated in the active layer is easily dissipated by using an AlN submount chip having a high thermal conductivity. In a normal laser, since the active layer is formed as a thin layer parallel to the substrate, the FFP has an elliptical shape that is long in the direction perpendicular to the substrate. In this embodiment, as described above, the FFP of a normal laser is used. FFP inclined by about 60 ° relative to the angle is obtained. In optical disk applications, etc., this FFP is collected in a circular shape, so there is no problem, but if the system requires an elliptical FFP perpendicular to the substrate surface, the output beam can be rotated using a diffraction grating or the like. That's fine.
[0028]
[Embodiment 2]
FIG. 3 shows a cross section of a nitride semiconductor laser according to another embodiment, corresponding to FIG. In this embodiment, a sapphire substrate 31 is used in place of the GaN substrate 10 of the previous embodiment. An n-type AlGaN buffer layer 11 is formed on the sapphire substrate 31 via an n-type GaN contact layer 32 in the same manner as in the previous embodiment. The element structure on the AlGaN buffer layer 11 is the same as that of the previous embodiment. However, since the sapphire substrate 31 is an insulator, the n-side electrode 19 is formed on the surface by performing hole etching until the n-type GaN contact layer 32 is exposed.
[0029]
Also in this embodiment, laser characteristics substantially similar to those of the previous embodiment can be obtained. Since the heat dissipation of the sapphire substrate is inferior to that of the GaN substrate, the operating current slightly increases, which may affect the characteristics in a high temperature environment. Moreover, although there is a risk that the yield may be lowered in the cleaving process or the chip forming process for forming the laser resonator, it has been confirmed that the method can basically be implemented with an insulating substrate.
[0031]
[Embodiment 3 ]
FIG. 4 shows a cross section of a nitride-based semiconductor laser according to another embodiment. In this embodiment, a high-power laser array is configured by forming a single chip including a plurality of active layers 15 formed on the n-type GaN substrate 10. The configuration and manufacturing process of each layer are the same as those in the first embodiment. However, the p-type semiconductor layer grown on the upper part of the stripe-shaped protrusion 23 is removed to form a void 51. This is for preventing a threading dislocation from the substrate 10 from entering the upper portion of the stripe-shaped protrusion 23 and causing deterioration of energization at the pn junction. The gap 51 may be embedded with an insulator such as SiO 2 or SiN.
[0032]
The n-side electrode 19 is formed in common for a plurality of laser element units each having one active layer 15. Each p-side electrode 18 is also connected to the submount 21 in common through the solder layer 20. Therefore, a plurality of laser element units are driven in parallel to obtain a high output.
[0033]
Specifically, a maximum output of 20 W or more can be obtained by configuring a laser array with about 100 active layers. However, in this case, the oscillation wavelength becomes wide multimode oscillation in the range of 396 nm to 410 nm due to fluctuations in the layer thickness and composition ratio of each element region. Such an array makes heat dissipation a problem, but this can be solved by using a Peltier forced cooler as the submount 21 instead of AlN.
[0037]
[Embodiment 4 ]
The GaN-based semiconductor laser of the type that includes a plurality of active layers and is driven in parallel as described in Embodiment 3 not only provides high output, but also has an oscillation wavelength range of 10 nm due to fluctuations in the composition of each active layer. Therefore, the present invention is effective particularly when applied to a projection type liquid crystal projector.
[0038]
FIG. 5 shows a projection type liquid crystal projector of such an embodiment. The output beams of the R, G, and B GaN-based semiconductor lasers 72a, 72b, and 72c are converted into circular beams by cylindrical lenses (or diffraction gratings) 73a, 73b, and 73c, respectively, and collimated lens systems 74a, 74b, and 74c. After collimation, the liquid crystal plates 71a, 71b and 71c for R, G and B are irradiated. Light transmitted through the liquid crystal plates 71 a, 71 b, 71 c enters the beam splitter 75 and is combined and enlarged and projected by the projection lens 76.
[0039]
Specifically, the semiconductor lasers 72a, 72b, and 72c are configured as three primary color laser arrays having center wavelengths of 630 nm, 520 nm, and 470 nm, respectively, by selecting the In composition of the InGaN quantum well layer of the active layer in the third embodiment. . By using this three-wavelength laser, the triangle on the chromaticity coordinates to be rendered can reproduce most of the colors that humans feel, but in particular, as described above, it becomes a multimode with an oscillation wavelength range of about 10 nm. Thus, the reproducible color range is further expanded.
[0040]
Specifically, if each of the R, G, and B semiconductor lasers 72a, 72b, and 72c includes 100 active layers and exceeds the maximum light output of 20 W, it can sufficiently withstand projection of 100 inches or more in daylight. This is because the light output for obtaining a luminous flux of 1000 lm is 5.5 W for red, 2.0 W for green, and 16.1 W for blue, even if the relative luminous efficiency is taken into consideration. At this time, the power consumption of the R, G, B semiconductor lasers 72a, 72b, 72c is 15 W, 8 W, and 91 W, respectively. This is a power consumption reduction of about 60% compared to about 200 W of a conventional indoor liquid crystal projector using a lamp light source. In addition, since the semiconductor laser can switch the light output by switching the amount of supply current, the brightness can be easily adjusted.
[0041]
The present invention is not limited to the above embodiment. For example, in the above embodiment, the step is formed in the buffer layer by anisotropic dry etching, but other methods can also be used. For example, a mask pattern (for example, SiO ₂ , SiN, etc.) is formed on the lower surface of the substrate or buffer layer, and Ga _x In _y Al _z B _1-xyz N (0 ≦ x , Y, z, x + y + z ≦ 1) A step can be similarly formed by selectively growing the layer. In addition to GaN and sapphire, a single crystal substrate such as GaAs, Si, SiC, diamond, or a ceramic substrate such as AlN can be used as the substrate. The present invention can be applied not only to a semiconductor laser but also to an LED.
[0042]
【The invention's effect】
As described above, according to the present invention, the active layer is epitaxially grown on the substantially vertical side surface of the step formed on the substrate with a growth surface inclined with respect to the substrate, and the influence of threading dislocation from the substrate is exerted. Therefore, a nitride-based semiconductor light-emitting device with low threshold current, high output, and high controllability of oscillation wavelength can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view and a plan view showing a structure of a semiconductor laser according to an embodiment of the present invention.
2A is a cross-sectional view showing a manufacturing step of the same embodiment; FIG.
FIG. 2B is a cross-sectional view showing a manufacturing step of the same embodiment;
FIG. 2C is a cross-sectional view showing a manufacturing step of the same embodiment;
FIG. 2D is a cross-sectional view showing a manufacturing step of the same embodiment;
FIG. 3 is a cross-sectional view of a semiconductor laser according to another embodiment.
FIG. 4 is a cross-sectional view of a semiconductor laser according to another embodiment.
FIG. 5 is a diagram showing a configuration of a projection type liquid crystal projector to which the semiconductor laser according to the present invention is applied.

Claims (10)

A substrate,
A buffer layer made of a nitride-based semiconductor formed on the substrate and having a step formed on a side surface substantially perpendicular to the surface;
A lower cladding layer epitaxially grown on a side surface of the step with a growth surface inclined with respect to the substrate;
An active layer made of a nitride semiconductor epitaxially grown with a growth surface inclined with respect to the substrate only on the inclined growth surface of the lower cladding layer ;
An upper cladding layer epitaxially grown over the active layer;
A semiconductor light emitting device comprising: a gap formed so as to penetrate the upper clad layer and reach the upper surface of the step . The semiconductor light emitting device according to claim 1, further comprising an insulating film embedded in the gap. A substrate,
A first conductivity type first Ga _x In _y Al _z B _1-xyz N (0 ≦ x, y, formed on the substrate and having a step with a side surface substantially perpendicular to the surface. z, x + y + z ≦ 1) a buffer layer made of a semiconductor,
A first conductivity type second Ga _x In _y Al _z B _1-xyz N (0 ≦ x, epitaxially grown with a growth surface inclined with respect to the substrate on the side surface of the step of the buffer layer. y, z, x + y + z ≦ 1) a lower cladding layer made of a semiconductor,
A third Ga _x In _y Al _z B _1-xyz N (0 ≦ x, y) that is epitaxially grown only on the inclined growth surface of the lower cladding layer and has a growth surface inclined with respect to the substrate. , Z, x + y + z ≦ 1) active layer made of a semiconductor,
Of the second conductivity type is epitaxially grown over the active layer fourth _{Ga x In y Al z B 1} -x-y-z N (0 ≦ x, y, z, x + y + z ≦ 1) based top of semiconductor A cladding layer;
And a gap formed so as to penetrate the upper cladding layer and reach the upper surface of the step. The semiconductor light emitting device according to claim 1, further comprising an insulating film embedded in the gap. Step of the buffer layer is a stripe-shaped protrusion, said active layer, a semiconductor light emitting device according to claim 1 or 4, wherein that are formed in a stripe shape along the side surface of the stripe-shaped projections . Include a plurality of active layers formed on said substrate, a semiconductor light emitting according to any one of claims 1 to 5 the plurality of active layers, characterized in that it is chip so as to be driven in parallel apparatus.   The semiconductor light-emitting device according to claim 1, wherein the active layer has a quantum well structure. A step of epitaxially growing a buffer layer made of a nitride-based semiconductor layer on the substrate;
Processing the step with a side surface substantially perpendicular to the surface of the buffer layer;
Epitaxially growing a lower cladding layer with a growth surface inclined with respect to the substrate on a side surface of the step of the buffer layer ;
Epitaxially growing an active layer made of a nitride-based semiconductor with a growth surface inclined with respect to the surface of the substrate only on the inclined growth surface of the lower cladding layer ;
Epitaxially growing an upper cladding layer covering the active layer;
Forming a gap so as to penetrate the upper cladding layer and reach the upper surface of the step . A method for manufacturing a semiconductor light emitting device, comprising: 9. The method of manufacturing a semiconductor light emitting device according to claim 8, further comprising a step of embedding an insulating film in the gap.  A projection display device comprising a combination of the semiconductor light-emitting device according to claim 1 and an optical system.