JP2011091251A - Nitride semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the stress applied to a nitride semiconductor layer from a substrate, and to improve the planarity of the nitride semiconductor layer and reduce the generation of cracks, in a nitride semiconductor light-emitting device in which the nitride semiconductor layer is laminated on a nitride semiconductor substrate. <P>SOLUTION: A first recess part 11, having a stripe-shaped aperture, is provided on a surface 10a of a substrate 10 constituted of a nitride semiconductor, and further, a second recess part 13, having an aperture and depth smaller than the first recess part 11, is provided on the entire surface 10a of the substrate 10, including the base of the first recess part 11. Furthermore, the second recess part 13 is planarized in a first semiconductor layer 30 on the lower layer side of a second semiconductor layer 40 having an active layer, as well as, a nitride semiconductor layer 20, constituted of the first semiconductor layer 30 and the second semiconductor layer 40, is layered on the surface 10a of the substrate 10 so that a recess part 41 is formed at a location corresponding to the recess part 11 on an upper-end face of the second semiconductor layer 40. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor light emitting device used for a laser device, a light emitting diode device, or the like.

Nitride semiconductor light emitting devices are expected to be used as light sources for optical disc devices such as Blu-ray (registered trademark), light sources for displays, and other light sources for exposure.
A nitride semiconductor light emitting device is manufactured by using a nitride semiconductor substrate as a growth substrate and laminating a nitride semiconductor layer on the surface thereof.
In general, nitride semiconductor light-emitting devices have a problem of low manufacturing yield. One of the reasons is that the lattice constant of the nitride semiconductor substrate and the lattice constant of the nitride semiconductor layer stacked on the surface do not completely match, or because of crystal distortion due to dislocation defects in the nitride semiconductor substrate. In other words, tensile strain is generated in the nitride semiconductor layer, and cracks are generated in the nitride semiconductor layer. In particular, when a mixed crystal having a high aluminum (Al) composition ratio is used for the nitride semiconductor layer, or even when the Al composition ratio is low, cracks are more likely to occur.
In order to solve such a problem, in Patent Document 1 (see paragraphs 0016 to 0019 and FIG. 1), a band-like groove is formed in a region including a dislocation concentration region (high dislocation density region) of a nitride semiconductor substrate. By stacking a nitride semiconductor layer on the surface of the nitride semiconductor substrate, the nitride semiconductor substrate is nitrided due to the difference in lattice constant between the nitride semiconductor substrate and the nitride semiconductor layer and tensile strain caused by dislocation of the nitride semiconductor substrate. A nitride semiconductor light emitting device is described that relieves stress applied to a nitride semiconductor layer and reduces the occurrence of cracks.

  Patent Document 2 (see paragraphs 0021 to 0024 and FIG. 3) describes a semiconductor light emitting device in which a multiple pattern structure is formed on the surface of a substrate such as sapphire and a nitride compound semiconductor is grown thereon. ing.

JP 2005-294416 A JP 2007-31784 A

  In Patent Document 1, by forming a groove in a region including a high dislocation density region of a nitride semiconductor substrate, stress applied to the nitride semiconductor layer stacked on the nitride semiconductor substrate can be reduced. Edge growth in which the nitride semiconductor layer rises occurs at the edge portion of the groove provided in the semiconductor substrate.

Here, edge growth will be described with reference to FIG. FIG. 10 is a schematic cross-sectional view showing a state in which a nitride semiconductor layer is stacked on a nitride semiconductor substrate in a conventional example.
As shown in FIG. 10, a nitride semiconductor substrate 210 in the conventional example in which a strip-like groove 211 extending in the direction perpendicular to the paper surface of FIG. 10 is provided along the high dislocation density region 210H is nitrided on the surface thereof. When the physical semiconductor layer 220 is stacked, an edge growth 221 in which the nitride semiconductor is raised and stacked is generated above the edge portion 213 of the groove 211.
When such edge growth 221 occurs, the generation of cracks cannot be sufficiently suppressed. Further, when the edge growth 221 occurs, the film thickness of the resist formed on the nitride semiconductor layer is likely to be non-uniform in the nitride semiconductor layer processing step, so that sufficient etching processing accuracy cannot be obtained. Due to these problems, a stable manufacturing yield of the nitride semiconductor light emitting device cannot be expected.

  Note that the multiple pattern structure formed on the substrate of the semiconductor light emitting device in Patent Document 2 is for efficiently extracting light emitted from the active layer to the outside of the semiconductor light emitting device. It is not intended to reduce the occurrence of cracks and edge growth in the nitride semiconductor layer, and to improve reliability and manufacturing yield.

  The present invention has been made in view of such problems, and an object of the present invention is to reduce the occurrence of cracks and edge growth in the nitride semiconductor layer, and to provide a highly reliable nitride semiconductor light emitting device and a high yield thereof. It is to provide a manufacturing method.

  In order to achieve the above object, a nitride semiconductor light emitting device according to claim 1 is a nitride semiconductor light emitting device including a substrate made of a nitride semiconductor and a nitride semiconductor layer stacked on the surface of the substrate. A first recess in the shape of a band formed on the surface of the substrate, and a plurality of second recesses formed on the bottom surface of the first recess and the protrusions that are the surface of the substrate other than the first recess, and nitriding The physical semiconductor layer has a first semiconductor layer and a second semiconductor layer having at least an active layer, and the first semiconductor layer is laminated so that a recess is formed at a position corresponding to the first recess on the upper end surface thereof. And configured.

According to such a configuration, the nitride semiconductor light-emitting element is configured by the nitride semiconductor layer stacked on the substrate provided with the first recess, and thus the substrate and the first semiconductor layer which is the lower layer portion of the nitride semiconductor layer, The strain applied to the first semiconductor layer in the region above the convex portion is relaxed by dividing the distortion due to the difference in lattice constant between the first concave portion and the first concave portion.
In addition, by providing the second recess, the lateral growth of the first semiconductor layer is promoted, and the vertical growth of the nitride semiconductor that causes the edge growth is suppressed, so that the occurrence of edge growth is reduced.
Furthermore, since the active layer is formed on the first semiconductor layer in which the stress applied from the substrate is relieved, the nitride semiconductor light emitting element performs a stable light emitting operation.
Moreover, since the 1st recessed part and the 2nd recessed part scatter the leakage light to a board | substrate, the stray light of the orthogonal | vertical direction in a nitride semiconductor light-emitting device is reduced.

  The nitride semiconductor light emitting device according to claim 2 is configured such that the first semiconductor layer is composed of a plurality of layers of nitride semiconductors in the nitride semiconductor light emitting device according to claim 1.

According to this configuration, the nitride semiconductor is stacked as a plurality of layers on the substrate on which the first recess and the second recess are formed.
Thereby, although the first semiconductor layer conventionally has a multi-layer structure in which cracks are likely to occur, the stress applied from the substrate to the first semiconductor layer is effectively relieved, and the occurrence of cracks is reduced.

  The nitride semiconductor light emitting device according to claim 3 is the nitride semiconductor light emitting device according to claim 1 or 2, wherein the upper end surface of the first semiconductor layer in the upper region of the convex portion is flattened. Configured.

According to this configuration, in the nitride semiconductor light emitting device, the second recess is embedded by the first semiconductor layer which is the lower layer of the nitride semiconductor layer, and the unevenness due to the second recess is flattened on the upper end surface of the first semiconductor layer. As described above, the first semiconductor layer is stacked on the surface of the substrate. Therefore, the active layer is formed on a flat surface that is flattened by embedding the second recess.
Thereby, the active layer has good uniformity of the emission mode in the plane, and emits light with uniform intensity and wavelength.

  The nitride semiconductor light-emitting device according to claim 4 is the nitride semiconductor light-emitting device according to any one of claims 1 to 3, wherein the second recess is parallel to the extending direction of the band-shaped first recess. And an opening that extends.

  According to this configuration, when the nitride semiconductor layer is stacked, the nitride semiconductor layer grows in the edge direction of the first recess, and the nitride semiconductor grows in the edge growth of the band-shaped first recess. The lateral growth to the belt-like second recess extending along the direction is effectively suppressed, and the occurrence of edge growth is effectively reduced.

  The nitride semiconductor light emitting device according to claim 5 is the nitride semiconductor light emitting device according to any one of claims 1 to 3, wherein the plurality of second recesses are intermittent without extending in a specific direction. It comprised so that it might have an opening.

  According to such a configuration, when the nitride semiconductor layer is stacked, the second recess is provided with intermittent growth of the nitride semiconductor layer in which the nitride semiconductor grows at the edge of the first recess. The occurrence of edge growth can be effectively reduced by the lateral growth.

  The nitride semiconductor light emitting device according to claim 6 is the nitride semiconductor light emitting device according to any one of claims 1 to 5, wherein the substrate has a high dislocation density region having a relatively high dislocation defect density. And a low dislocation density region having a dislocation defect density lower than that of the high dislocation density region, and the first recess is provided in the region having the high dislocation density region.

According to this configuration, the convex portion of the substrate is formed in the low dislocation density region other than the first concave portion including the high dislocation density region. Therefore, when the nitride semiconductor layer is stacked, strain due to the difference in lattice constant between the substrate and the nitride semiconductor layer is accumulated in the nitride semiconductor stacked in the first recess, and the dislocations in the high dislocation density region The influence of the defect is stopped in the first recess.
As a result, it is possible to prevent the influence caused by strain and dislocation defects generated when the nitride semiconductor layers are stacked from spreading to the nitride semiconductor layer stacked in the region above the convex portion of the substrate.

  The nitride semiconductor light emitting device according to claim 7 is the nitride semiconductor light emitting device according to any one of claims 1 to 6, wherein the surface of the substrate is a C plane of the nitride semiconductor, The extending direction of the first recess was configured to be perpendicular to the M-plane of the nitride semiconductor.

  According to such a configuration, the wall surface of the belt-shaped first recess is formed by the A plane orthogonal to the M plane, and the M plane is not exposed. Since there is no exposure of the M surface, the occurrence of cracks from the wall surface of the first recess is reduced. Further, when the nitride semiconductor light emitting element has a laser element structure, the resonator end face for laser oscillation can be formed by cleaving the M plane. Laser oscillation using

  The nitride semiconductor light emitting device according to claim 8 is the nitride semiconductor light emitting device according to claim 7, wherein the wall surface of the second recess is formed of a surface not parallel to the M-plane of the nitride semiconductor.

  According to such a configuration, since the second recess is provided so that the M surface is not exposed, generation of cracks from the wall surface of the second recess is prevented.

  The nitride semiconductor light emitting device according to claim 9 is the nitride semiconductor light emitting device according to any one of claims 1 to 8, wherein the first semiconductor layer includes a nitride semiconductor containing Al. The configuration.

  According to this configuration, the first semiconductor layer includes the nitride semiconductor containing Al having a large lattice constant difference from the nitride semiconductor normally used as the substrate, and the edge growth at the edge portion of the first recess is performed. The stress applied from the substrate to the first semiconductor layer is relaxed while suppressing the occurrence of.

  The nitride semiconductor light emitting device according to claim 10 is the nitride semiconductor light emitting device according to claim 9, wherein the second recess is embedded by a nitride semiconductor containing Al of the first semiconductor layer. Configured.

According to such a configuration, a layer made of a nitride semiconductor containing Al having a large lattice constant difference from a nitride semiconductor normally used as a substrate is grown and stacked so as to fill the second recess.
This effectively relieves the stress on the layer from the substrate due to strain based on the difference in lattice constant from the substrate.

  The nitride semiconductor light-emitting device according to claim 11 is the nitride semiconductor light-emitting device according to any one of claims 1 to 10, wherein the second semiconductor layer is formed in the first recess at the upper end surface thereof. The layers were laminated so that the concave portions were formed at the corresponding positions.

  According to such a configuration, the second semiconductor layer includes the nitride semiconductor layer stacked on the first semiconductor layer in which the recess is formed at a position corresponding to the first recess. Distortion due to the difference in lattice constant between the semiconductor layer and the first semiconductor layer is divided by a recess formed at a position corresponding to the first recess of the first semiconductor layer, so that the first semiconductor layer and the first semiconductor layer are separated from each other. The stress applied to the second semiconductor layer in the region above the convex portion from the substrate is relaxed.

  The nitride semiconductor light emitting device according to claim 12 is the nitride semiconductor light emitting device according to claim 11, wherein the nitride semiconductor light emitting device is divided along a recess formed in an upper end surface of the second semiconductor layer. Configured.

  According to this configuration, the nitride semiconductor light emitting element is divided along the recess formed in the upper end surface of the second semiconductor layer, that is, along the first recess. Since the concave portion based on the first concave portion formed in the nitride semiconductor layer serves as a cutting allowance for the nitride semiconductor light emitting device chip, the active layer in the chip is provided in a region not affected by the concave and convex portions by the first concave portion. Become. As a result, the nitride semiconductor light emitting device has good emission mode uniformity and emits light with uniform intensity and wavelength.

  The nitride semiconductor light emitting device according to claim 13 is the nitride semiconductor light emitting device according to any one of claims 1 to 12, wherein the second semiconductor layer emits laser light in a region above the convex portion. For this reason, a resonator is provided.

  According to this configuration, the nitride semiconductor light emitting element has a laser element structure, and the resonator is provided in a region avoiding the recess of the nitride semiconductor layer based on the first recess. As a result, the nitride semiconductor light emitting device oscillates with a stable intensity and wavelength.

  According to the first aspect of the present invention, since the stress applied to the nitride semiconductor layer from the substrate is relieved, the occurrence of cracks in the nitride semiconductor layer is reduced, and as a result, the nitride semiconductor light-emitting device due to the occurrence of cracks Therefore, a highly reliable nitride semiconductor light emitting device can be obtained. Further, since the occurrence of edge growth is reduced, the processing accuracy of a device fabricated on the nitride semiconductor layer is improved, and a nitride semiconductor light emitting element with stable quality can be obtained. Furthermore, a stable quality nitride semiconductor light-emitting device having good light emission intensity and wavelength uniformity from the active layer can be obtained. Further, since stray light is reduced, the intensity of light emitted from the active layer and the uniformity of wavelength can be improved. Moreover, since the critical film thickness with respect to cracks can be increased, the film thickness of the nitride semiconductor layer can be increased, or a nitride semiconductor having a high Al composition ratio can be used.

According to the second aspect of the present invention, since the generation of cracks is reduced while the first semiconductor layer is constituted by a plurality of layers, a nitride semiconductor light emitting device having a high degree of freedom in materials and the like is obtained. It is done.
According to the third aspect of the present invention, a stable quality nitride semiconductor light emitting device having good light emission intensity and wavelength uniformity from the active layer can be obtained.
According to the invention described in claim 4 or claim 5, since the occurrence of edge growth is effectively reduced, a nitride semiconductor light emitting device having a reliable and stable quality can be obtained.
According to the invention described in claim 6, in the case of using a substrate having a high dislocation density region, the generation of edge growth is reduced while preventing the generation of cracks due to the spread of dislocation defects. Stable quality nitride semiconductor light emitting devices can be obtained.
According to the seventh aspect of the present invention, since the generation of cracks is reduced, a highly reliable nitride semiconductor light emitting device can be obtained.
According to the invention described in claim 8, since the occurrence of cracks from the wall surface of the second recess is prevented, the occurrence of edge growth can be reduced without generating new cracks. A nitride semiconductor light emitting device with high reliability and stable quality can be obtained.

According to the ninth aspect of the present invention, even when the first semiconductor layer includes an Al-containing nitride semiconductor having a large difference in lattice constant from the nitride semiconductor constituting the substrate, generation of cracks or Since the occurrence of edge growth can be reduced, a nitride semiconductor light emitting device with a high degree of freedom of materials can be obtained.
According to the invention described in claim 10, since the stress applied from the substrate to the layer made of the nitride semiconductor containing Al that generates particularly large strain is effectively relaxed and the generation of cracks is reduced, The composition ratio can be increased.
According to the eleventh aspect of the present invention, since the stress applied to the second semiconductor layer in the upper region of the convex portion from the substrate through the first semiconductor layer and through the first semiconductor layer can be relaxed, A highly reliable nitride semiconductor light-emitting device with reduced generation can be obtained.
According to the twelfth aspect of the present invention, there can be obtained a nitride semiconductor light emitting device having a stable quality with good light emission intensity and wavelength uniformity from the active layer.
According to the thirteenth aspect of the present invention, there can be obtained a nitride semiconductor light emitting device having a stable quality in which the intensity and wavelength uniformity of the laser oscillation light from the resonator is good.

It is typical sectional drawing which shows the mode of the state which laminated | stacked the nitride semiconductor layer on the nitride semiconductor substrate in 1st Embodiment which concerns on this invention. It is the typical top view which looked at the nitride semiconductor substrate in a 1st embodiment concerning the present invention from the upper part. 1 is a schematic perspective view of a nitride semiconductor substrate according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a nitride semiconductor light emitting device in a first embodiment according to the present invention. It is explanatory drawing for demonstrating the crystal orientation and crystal plane of the nitride semiconductor which concern on this invention. It is typical sectional drawing which shows the manufacturing process of the nitride semiconductor light-emitting device in 1st Embodiment concerning this invention, (a) is the nitride semiconductor substrate before a process, (b) is a 1st recessed part formation process, (c ) Shows a second recess forming step, (d) shows a first semiconductor layer forming step, and (e) shows a second semiconductor layer forming step. It is the typical top view which looked at the nitride semiconductor substrate in a 2nd embodiment concerning the present invention from the upper part. It is typical sectional drawing of the nitride semiconductor light-emitting device in 3rd Embodiment concerning this invention. It is a typical sectional view of the nitride semiconductor light emitting element in a 4th embodiment concerning the present invention. It is typical sectional drawing which shows the mode of the state which laminated | stacked the nitride semiconductor layer on the nitride semiconductor substrate in a prior art example.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings as appropriate.
<Configuration>
First, referring to FIGS. 1 to 3, a configuration of a nitride semiconductor substrate (hereinafter simply referred to as a substrate) 10 and a nitride semiconductor layer 20 stacked on a surface 10 a of the substrate 10 according to the first embodiment of the present invention. Will be described.

  As shown in FIGS. 1 to 3, the substrate 10 according to the first embodiment includes a band-shaped first recess 11 having a width W2 and a depth D1 on the surface 10 a and the first recess 11 on the surface 10 a of the substrate 10. A first hill portion (convex portion) 12 having a width W1, which is a region, is formed. Further, the entire region of the surface 10a of the substrate 10, that is, the bottom surface of the first recess 11 and the surface of the first hill portion 12, the first recess 11 having a width W5 (<W2) and a depth D2 (<D1). A second recess 13 is formed in which grooves having openings extending in a direction parallel to the strip-shaped extending direction are arranged in a stripe pattern. The second recess 13 has a smaller width and depth than the first recess 11 (W5 <W2, D2 <D1). Moreover, the adjacent 2nd recessed parts 13 are formed across the 2nd hill part 14 of width W4.

  When the nitride semiconductor layer 20 having a lattice constant different from that of the substrate 10 is stacked on the surface 10 a of the substrate 10, the first concave portion 11 is distorted due to a difference in lattice constant between the substrate 10 and the nitride semiconductor layer 20. It is provided in order to relieve the stress applied to the nitride semiconductor layer 20 from the substrate 10.

  This stress is determined by the difference between the lattice constant between the substrate 10 and the nitride semiconductor layer 20 and the area where both are in contact. By providing the first recess 11, it is possible to reduce the area where the surface 10 a of the substrate 10 and the nitride semiconductor layer 20 are continuously in contact with each other while being distorted. Can be relaxed. That is, when the nitride semiconductor layer 20 is formed, the nitride semiconductor is grown in the lateral direction of the substrate 10 (the inner side of the first recess 11) and stacked, so that the nitride grown laterally in the first recess 11 Distortion accumulates in the physical semiconductor. For this reason, the strain in the contact portion between the substrate 10 and the nitride semiconductor layer 20 other than the first recess 11 is divided by the first recess 11. As a result, since the continuous area decreases on the same surface that is in contact with the substrate 10 and the nitride semiconductor layer 20 while being distorted, particularly above the first hill 12 that is a region other than the first recess 11. The stress applied from the substrate 10 to the nitride semiconductor layer 20 stacked in the region is relieved.

  Further, the substrate 10 includes a high dislocation density region 10H in which dislocation defects of the nitride semiconductor crystal penetrating from the back surface 10b to the front surface 10a of the substrate 10 are generated at a high density, and a low dislocation density region 10L with few dislocation defects. It is repeated alternately. The first recess 11 is formed in a region having a width W2 (W2> W3) so as to completely include the high dislocation density region 10H having the width W3 and including a part of the adjacent low dislocation density region 10L. Has been. Further, the entire first hill portion 12 having the width W1 is formed in the low dislocation density region 10L.

  By forming the first recess 11 so as to include the high dislocation density region 10H in which dislocation defects are concentrated, the dislocation defect spreads to the portion of the nitride semiconductor layer 20 stacked in the upper region of the first hill portion 12. Can be prevented.

In the first embodiment, the first recess 11 is formed in a region including the high dislocation density region 10H, but the first recess 11 is also formed in the low dislocation density region 10L intermediate between the adjacent high dislocation density regions 10H. The recess 11 may be formed. In this case, the first recess 11 formed in the low dislocation density region 10L need not completely include the high dislocation density region, and may be formed with a width smaller than the width W2.
Alternatively, the first recesses 11 may be formed at appropriate intervals using the substrate 10 made of a low dislocation density nitride semiconductor without the high dislocation density region 10H.

In the substrate 10, the number of dislocations (dislocation density) per unit area of the low dislocation density region 10L is 1 × 10 ⁷ / cm ² or less, preferably 5 × 10 ⁶ / cm ² or less, more preferably 1 × 10 ⁶ / cm ² or less. The high dislocation density region 10H is a region having a higher dislocation density than the low dislocation density region 10L, and the dislocation density is not particularly limited.
The dislocation density can be measured by CL (cathode luminescence) observation.

The substrate 10 is a substrate made of a nitride semiconductor such as GaN, AlGaN, AlN, GaInN, AlGaInN, and AlBGaInN, and has a composition that exhibits good lattice matching with the nitride semiconductor layer 20 formed on the substrate 10. The one is selected. The substrate 10 may be doped with n-type impurities such as Si, Ge, and O. When impurities are doped, the concentration thereof is not particularly limited, but for example, about 5 × 10 ¹⁵ / cm ^{3 to} 5 × 10 ²¹ / cm ³ is appropriate. Furthermore, the shape of the substrate 10 is a disk shape or a square plate shape. In the manufacturing process, the size of the wafer serving as the substrate 10 is 1 inch (2.54 cm) or more, preferably 2 inches (5.08 cm) or more. Further, the thickness of the wafer is preferably 50 μm or more.
Furthermore, the substrate 10 may have a structure of two or more layers. For example, a nitride semiconductor layer laminated on a different substrate or a semiconductor layer having two or more semiconductor layers may be used. A so-called template substrate may be used. Further, another metal substrate may be bonded after the nitride semiconductor layer is stacked on the substrate.
The material of the substrate 10 is preferably selected in consideration of light absorption by wavelength. For example, in order to extract light efficiently, a substrate that absorbs less light in that wavelength region is selected. From such a viewpoint, if the emission (oscillation) wavelength is in the ultraviolet region, it is preferable to use AlN rather than GaN.

  The depth D1 of the first recess 11 is usually about 0.5 μm to 10.0 μm, preferably 1.0 μm to 6.0 μm. The first recess 11 is formed so as to include the high dislocation density region 10H so that its width W2 is wider than the width W3 of the high dislocation density region 10H (W2> W3).

  Moreover, what is necessary is just to match | combine the space | interval of 1st recessed parts 11, ie, width W1, with the space | interval of the high dislocation density area | region 10H, when using the board | substrate 10 which has the high dislocation density area | region 10H. When using the substrate 10 composed of only the low dislocation density region 10L, the stress relaxation effect can be obtained by providing at least one first recess 11 in the wafer. This effect increases as the width W1 is reduced. However, the area of the first hill portion 12 for forming the nitride semiconductor light emitting element is narrowed, and the number of elements formed per wafer is not reduced too much. The width W1 can be, for example, about 100 μm to 20 mm so that at least one element can be formed on the hill portion 12.

The second recess 13 is formed as a recess smaller than the first recess 11 on the bottom surface of the first recess 11 and the surface of the first hill portion 12.
By providing the first recess 11, edge growth in which the nitride semiconductor layer 20 swells occurs in the region above the edge portion of the first recess 11. In this embodiment, in order to reduce this edge growth, the 2nd recessed part 13 is provided.

  The depth D2 of the second recess 13 is usually about 0.1 μm to 1 μm, preferably 0.1 μm to 0.5 μm. The width W5 of the second recess 13 is about 1 μm to 10 μm. Further, the interval between the second recesses 13, that is, the width W 4 of the second hill portion 14 can be set to be approximately the same as the width W 5 of the second recess 13.

  By providing the second recess 13 and promoting the lateral growth to fill the second recess 13 with a nitride semiconductor material, the vertical growth of the nitride semiconductor layer 20 at the edge portion of the first recess 11 is suppressed. In addition, the amount of rising edge growth can be reduced. In addition, by growing the nitride semiconductor laterally so as to fill the second recess 13, the stress applied from the substrate 10 to the nitride semiconductor layer 20 in the laterally grown layer can be relaxed.

Further, the surface 10a of the substrate 10 on which the nitride semiconductor layer 20 is laminated is preferably a (0001) plane (C plane) in the hexagonal system of the nitride semiconductor, as shown in FIG.
Further, the end surface of the first recess 11 (the surface parallel to the cross section of the substrate 10 shown in FIG. 1) is the (1-100) plane (M plane), so that it is formed on the nitride semiconductor layer 20. When the resonator 42 (see FIG. 4) is formed using a ridge structure described later, the resonator end face can be formed by cleavage.

  Further, when the C plane is the surface (main surface) 10a of the substrate 10, the nitride semiconductor layer 20 is grown in the lateral direction, which is the spreading direction of the substrate surface, so that the dislocations are perpendicular to the crystal orientation <0001>. appear. That is, dislocation occurs in the direction of crystal orientation <11-20> or <1-100>. In the region where the nitride semiconductor layer 20 is grown in the lateral direction, dislocations are generated in these crystal orientations, so that strain applied to the crystals can be divided and stored in the dislocation portions. Further, as the width of the growth region in the lateral direction is larger, the crystal growth rate X in the vertical direction (perpendicular to the surface 10a of the substrate 10) is smaller than the crystal growth rate Y in the lateral direction (X <Y). And the effect which suppresses distortion becomes large, so that ratio Y / X is large.

The nitride semiconductor layer 20 is laminated on the surface 10a of the substrate 10, and a nitride semiconductor for constituting a nitride semiconductor light emitting element is appropriately laminated. For example, the nitride semiconductor light emitting device 1 shown in FIG. 4 is a nitride semiconductor laser device, and the nitride semiconductor layer 20 includes an underlayer 50 (first n-type semiconductor layer) and an n-type cladding layer 60 ( Second n-type semiconductor layer), n-type light guide layer 70 (third n-type semiconductor layer), active layer 80, p-type cap layer 90 (first p-type semiconductor layer), p-type light guide layer 100 (Second p-type semiconductor layer), p-type cladding layer 110 (third p-type semiconductor layer), and p-type contact layer 120 (fourth p-type semiconductor layer). Here, for convenience of explanation, the active layer 80 that generates light is not included, the lower layer than the active layer 80 is the first semiconductor layer 30, and the upper layer including the active layer 80 is the second semiconductor layer 40.
Hereinafter, the description will be continued with reference to FIG.

  The first semiconductor layer 30 is configured by sequentially laminating a base layer 50, an n-type cladding layer 60, and an n-type light guide layer 70 on the surface 10 a of the substrate 10. In the upper end surface 30 a of the first semiconductor layer 30 stacked in the upper region of the first recess 11, a recess 31 is formed at a position corresponding to the first recess 11. The second recess 13 is embedded in the first semiconductor layer 30, and the upper end surface 30 a in the upper region of the first hill portion 12 is flattened.

A first recess 11 is formed on the surface 10 a of the substrate 10, and a nitride semiconductor is stacked to such an extent that a recess 31 is formed at a position corresponding to the first recess 11 on the upper end surface 30 a of the first semiconductor layer 30. Therefore, the first semiconductor layer 30 stacked on the surface 10a side of the substrate 10 is relieved of stress caused by distortion between the first semiconductor layer 30 and the substrate 10. Moreover, since the 1st recessed part 11 is formed so that the high dislocation density area | region 10H where a dislocation defect concentrates may be included, the dislocation defect to the 1st semiconductor layer 30 laminated | stacked on the upper area | region of the 1st hill part 12 is carried out. Can be prevented. Furthermore, since the second recess 13 is formed, the occurrence of edge growth in which the first semiconductor layer 30 rises at the edge portion of the first recess 11 is reduced.
In particular, the upper end surface 30 a of the first semiconductor layer 30 stacked in the upper region of the first hill portion 12 of the substrate 10 is a flat surface without leaving the influence of the first recess 11 and the second recess 13.

  Whether each layer of the nitride semiconductor layer 20 is divided into the first semiconductor layer 30 is determined depending on whether the second recess 13 is buried below the active layer 80 and at least on the upper end surface of the first semiconductor layer 30. For convenience, it is determined by whether or not it is flattened. That is, at least a lower layer than the layer including the layer in which the second recess 13 is planarized is divided into the first semiconductor layer 30. The layer above the layer where the second recess 13 is planarized and below the active layer 80 may be divided into either the first semiconductor layer 30 or the second semiconductor layer 40. Therefore, for example, when the second recess 13 is filled and planarized by the upper end surface of the lowermost underlayer 50 as in the first embodiment shown in FIG. The semiconductor layer 40 may be divided into two semiconductor layers 40, and the lower layer from the n-type cladding layer 60 and the lower layer from the n-type light guide layer 70 adjacent to the active layer 80 may be divided into the first semiconductor layer 30. In other words, the second recess 13 only needs to be flattened up to the uppermost layer of the first semiconductor layer 30, and may be flattened at a lower layer, for example, the lowermost layer.

  In the second semiconductor layer 40, an active layer 80, a p-type cap layer 90, a p-type light guide layer 100, a p-type cladding layer 110, and a p-type contact layer 120 are sequentially stacked on the upper end surface 30 a of the first semiconductor layer 30. Configured. On the upper end surface 40 a of the second semiconductor layer 40, a recess 41 is formed at a position corresponding to the recess 31 of the first semiconductor layer 30 as a lower layer, that is, a position corresponding to the first recess 11 of the substrate 10. In addition, since the concave portion based on the second concave portion 13 is flattened on the upper end surface 30a of the first semiconductor layer 30, the second semiconductor layer 40 is based on the second concave portion 13 over the entire region in the thickness direction. A recess does not occur.

On the upper end surface 30 a of the first semiconductor layer 30 on which the second semiconductor layer 40 is stacked, a recess 31 is formed at a position corresponding to the first recess 11. For this reason, also in the 2nd semiconductor layer 40, the distortion by the difference in a lattice constant between lower layers is reduced, and the stress received from the board | substrate 10 through a lower layer is relieve | moderated.
In addition, since the second recess 13 is embedded and planarized in the upper end surface 30a of the first semiconductor layer 30, the active layer 80, which is the lowermost layer of the second semiconductor layer 40 stacked on the upper end surface, and Furthermore, the flatness of the upper layer is ensured. For this reason, in-plane light emission distribution with good uniformity is obtained, and since the uniformity of the light emission mode is good, the unity of the light emission wavelength is also good.

  As described above, the first concave portion 11 and the second concave portion 13 are provided on the surface 10a of the substrate 10, and the nitride semiconductor layer 20 is laminated thereon, thereby suppressing the occurrence of cracks in the nitride semiconductor layer 20. be able to. Moreover, the film thickness of each layer constituting the nitride semiconductor layer 20 can be increased within the allowable range of the number of cracks. In particular, it is useful when a nitride semiconductor having a high Al composition ratio and a large difference in lattice constant from the nitride semiconductor normally used as the substrate 10 is stacked.

  Next, the configuration of the nitride semiconductor light emitting device 1 of the first embodiment of the present invention will be described with reference to FIG. 4 (refer to FIGS. 1 to 3 as appropriate).

(Configuration of nitride semiconductor light emitting device)
In the nitride semiconductor light emitting device 1 of the first embodiment shown in FIG. 4, a nitride semiconductor layer 20 is stacked on the surface 10 a of the substrate 10 made of a nitride semiconductor. The upper end surface of the nitride semiconductor layer 20 is covered with a protective film 160 except for a part thereof, and the wall surface of the nitride semiconductor layer 20 is covered with a protective film 170 except for a part thereof. A part of the upper end surface of the nitride semiconductor layer 20 is in ohmic contact with the p-side electrode 130, and the p-side electrode 130 is electrically connected to the p-side pad electrode 140. Further, on the back surface 10b of the substrate 10, the n-side electrode 150 is in ohmic contact with the substrate 10 and both are electrically connected.

The substrate 10 is cut from the nitride semiconductor substrate 10 shown in FIG. 1 to FIG. 3 by forming the nitride semiconductor light emitting device 1 into chips, and is formed on both sides with the first hill portion 12 as the center. One recess 11 is formed. In addition, a plurality of second recesses 13 arranged in a stripe pattern are formed on the surface 10 a of the substrate 10, that is, on the surface of the first hill portion 12 and the bottom surface of the first recess 11.
A nitride semiconductor layer 20 is stacked on the surface 10 a of the substrate 10, and the substrate 10 is connected to the nitride semiconductor layer 20 by an underlayer 50. In addition, the substrate 10 in the first embodiment is conductive and is electrically connected to the n-side electrode 150 provided on the back surface 10b side.

The nitride semiconductor layer 20 includes a first semiconductor layer 30 in which an underlayer 50, an n-type cladding layer 60, and an n-type light guide layer 70 are stacked in order from the substrate 10 side, an active layer 80, and a p-type cap layer 90. , A p-type light guide layer 100, a p-type cladding layer 110, and a p-type contact layer 120 are stacked to form a second semiconductor layer 40.
Further, for example, a buffer layer (not shown) is appropriately formed between the substrate 10 and the underlayer 50, and a crack prevention layer (not shown) is appropriately formed between the underlayer 50 and the n-type cladding layer 60. May be. Further, some of these layers may be omitted as appropriate.

The underlayer 50 is a layer for electrically connecting the nitride semiconductor layer 20 and the conductive substrate 10. The underlayer 50 preferably has a composition larger than the band gap energy of the active layer 80, and Al _a Ga _1-a N (0 ≦ a <0.3) is an example. This underlayer 50 may also be used as the n-type cladding layer 60. For example, when the oscillation wavelength is in the ultraviolet region of about 370 nm, about Al _a Ga _1-a N (0 ≦ a <0.15) is preferable, and when not using the n-type cladding layer 60, Al _a Ga _{About 1-a} N (0 ≦ a <0.05) is preferable. Further, a crack preventing layer (not shown) containing In may be formed on the underlayer 50.
Further, in the case where the underlayer 50 is a layer made of a nitride semiconductor containing Al, by embedding the second recess 13 with this layer, the nitride layer containing Al is contained while the first recess 11 is included. The stress applied to the nitride semiconductor layer 20 from the substrate 10 can be more effectively reduced while suppressing the occurrence of edge growth at the edge portion. Since the Al composition ratio can be increased in a layer below the active layer 80, the effect of the present invention becomes more remarkable.
For example, when the oscillation wavelength is in the ultraviolet region of about 370 nm and the Al layer is contained in the underlayer 50, and when the n-type cladding layer 60 is not used, Al _a Ga _1-a N (0 <a <0. 05), when the n-type cladding layer 60 is also used, it is preferably about Al _a Ga _1-a N (0.05 <a <0.15). Further, when the oscillation wavelength is about 488 nm, it is preferably about Al _a Ga _1-a N (0 <a <0.1) when also used as the n-type cladding layer 60.

The n-type cladding layer 60 is a layer that injects electrons into the active layer 80 via the n-type light guide layer 70. The n-type cladding layer 60 preferably contains Al. Further, it may be a single layer or a multilayer layer (superlattice structure). The n-type impurity concentration is not particularly limited, but is preferably 1 × 10 ¹⁷ to 1 × 10 ²⁰ / cm ³ , and the n-type impurity concentration may be inclined in the film thickness direction. Further, it may function as a clad layer for confining electrons by providing a composition gradient of Al.

The n-type light guide layer 70 is provided as a layer in which electrons injected from the n-type clad layer 60 are confined in the active layer 80 and light generated in the active layer 80 is not confined. The n-type light guide layer 70 is formed by growing Al _a Ga _1-a N (0 ≦ a ≦ 1). The film thickness of the n-type light guide layer 70 is not particularly limited, and an arbitrary film thickness can be selected. For example, the film thickness can be about 0.15 μm. This layer can be formed of a single layer or a multilayer layer (superlattice structure). Further, an n-type impurity may be doped. However, the n-type light guide layer 70 may be omitted depending on the composition and thickness of the active layer 80. In addition, when the laser oscillation wavelength is a wavelength band of 440 nm or more, the n-type light guide layer 70 is preferably made of In _a Ga _1-a N (0 ≦ a ≦ 1).

  In addition, in the upper end surface 30a of the n-type light guide layer 70 that is the uppermost layer of the first semiconductor layer 30, the first recess 11 provided in the surface 10a of the substrate 10 is not embedded and the recess 31 remains. On the other hand, the 2nd recessed part 13 is embedded, and the upper area | region of the 1st hill part 12 of the upper end surface 30a is planarized.

The active layer 80 is injected from the n-type cladding layer 60 via the n-type light guide layer 70 and from the p-type cladding layer 110 via the p-type light guide layer 100 and the p-type cap layer 90. It is a layer that recombines with holes to generate light. The active layer 80 may be either a single (SQW) or multiple quantum well structure (MQW). For example, _a well layer composed of Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, a + b ≦ 1), and Al _c In _d Ga _1-cd N (0 ≦ and a quantum well structure including a barrier layer of c ≦ 1, 0 ≦ d ≦ 1, c + d ≦ 1). The semiconductor layer used for the active layer 80 may be any of undoped, n-type impurity doped, and p-type impurity doped, but is preferably undoped or n-type impurity doped. Thereby, a high-power nitride semiconductor light emitting device 1 can be obtained. Furthermore, the well layer may be undoped and the barrier layer may be n-type impurity doped. Thereby, the output and luminous efficiency of the light emitting element can be increased. In addition, by including Al in the well layer, it is possible to obtain a wavelength range that is difficult for a conventional InGaN well layer, specifically, a wavelength near 365 nm, which is the band gap energy of GaN, or shorter. .

For example, when the barrier layer is doped with an n-type impurity, the concentration is preferably at least 5 × 10 ¹⁶ / cm ³ or more. Further, in the high-power nitride semiconductor light-emitting element 1, 5 × 10 ¹⁷ / cm ³ or more and 1 × 10 ²⁰ / cm ³ or less are appropriate. When the n-type impurity is doped in the barrier layer, all the barrier layers in the active layer 80 may be doped, or a part may be doped and a part may be undoped.

The p-type cap layer 90 is a layer that prevents the carriers injected into the active layer 80 from overflowing even if the band gap is large, the temperature of the nitride semiconductor light emitting device 1 rises, and the injected charge density increases. The p-type cap layer 90 is preferably made of Mg-containing Al _a Ga _1-a N (0 ≦ a ≦ 1) and has a thickness of about 100 mm through which holes can pass through the tunnel effect. However, the p-type cap layer 90 may be omitted depending on the composition and film thickness of the active layer 80.

The p-type light guide layer 100 is a layer in which holes injected from the p-type cladding layer 110 into the active layer 80 are confined in the active layer 80 and light generated in the active layer 80 is not confined. The p-type light guide layer 100 is formed of Al _a Ga _1-a N (0 ≦ a ≦ 1). The p-type light guide layer 100 is preferably grown as undoped, but may be doped with Mg. Similarly to the n-type light guide layer 70, it can be formed of a single layer or a multilayer film layer (superlattice structure). Furthermore, the p-type light guide layer 100 can be omitted depending on the composition, film thickness, etc. of the active layer 80. In addition, when the wavelength of laser oscillation is a wavelength band of 440 nm or more, the n-type light guide layer 70 is preferably made of In _a Ga _1-a N (0 ≦ a ≦ 1).

  The p-type light guide layer 100 and the p-type cladding layer 110 and the p-type contact layer 120 form a linear ridge structure extending in the direction perpendicular to the paper surface of FIG. This ridge structure constitutes the optical waveguide of the resonator 42.

The p-type cladding layer 110 is a layer that injects holes into the active layer 80 via the p-type light guide layer 100 and the p-type cap layer 90. The p-type cladding layer 110 is not particularly limited as long as it has a composition larger than the band gap energy of the active layer 80 and can confine holes in the active layer 80. As an example, Al _a Ga _1-a N (0 ≦ a <1). The p-type impurity concentration of the p-type cladding layer 110 is suitably 1 × 10 ¹⁸ to 1 × 10 ²¹ / cm ³ . When the p-type impurity concentration is in the above range, the bulk resistance can be reduced without reducing the crystallinity. The p-type cladding layer 110 may be a single layer or a multilayer film layer (superlattice structure). In the case of a multilayer film layer, it may be a multilayer film layer composed of the aforementioned Al _a Ga _1-a N and a nitride semiconductor having a smaller band gap energy. For example, as a nitride semiconductor having a small band gap energy, as in the case of the n-type cladding layer 60, In _a Ga _1-a N (0 ≦ a <1), Al _b Ga _1-b N (0 ≦ b <1). In addition, when the p-type cladding layer 110 is a multilayer film composed of a layer having a large band gap energy and a layer having a small band gap energy, p-type impurities are added to at least one of the layer having a large band gap energy and the layer having a small band gap energy. You may dope. When doping both the layer with large band gap energy and the layer with small band gap energy, the doping amount may be the same or different.

  The p-type cladding layer 110 forms a ridge structure that constitutes the optical waveguide of the resonator 42 together with the upper portion of the p-type light guide layer 100 and the p-type contact layer 120.

The p-type contact layer 120 is a layer whose upper end surface is in ohmic contact with the p-side electrode 130 and is electrically connected to the p-side electrode 130. The p-type contact layer 120 forms a ridge structure that constitutes the optical waveguide of the resonator 42 together with the upper part of the p-type light guide layer 100 and the p-type cladding layer 110. Further, the upper end surface of the p-type contact layer 120 is in ohmic contact with the p-side electrode 130.
Examples of the p-type contact layer 120 include Al _a Ga _1-a N (0 ≦ a <1) containing a p-type impurity.

The resonator 42 is a resonator for confining light generated in the active layer 80 and causing laser oscillation. The resonator 42 in the first embodiment constitutes a Fabry-Perot resonator.
The resonator 42 uses a ridge structure formed by the upper part of the p-type light guide layer 100, the p-type cladding layer 110, and the p-type contact layer 120 as an optical waveguide. A reflective film (not shown) made of, for example, a dielectric film made of Al ₂ O ₃ or the like is formed on the end face on the near side in the direction perpendicular to the paper surface of FIG. 4 of this ridge structure. This reflection film functions as a half mirror, and the end surface on the near side becomes a light emission side end surface that emits a part of the light confined in the resonator 42 to the outside. In addition, a reflection film (not shown) in which SiO ₂ and ZrO ₂ are alternately laminated on a dielectric film made of, for example, Al ₂ O ₃ is formed on the end surface of the ridge structure in the vertical direction on the paper surface. ing. This end surface on the heel side becomes the light reflection side end surface of the resonator 42.

  The resonator 42 is provided in the upper region of the first hill portion 12 and is formed so as not to be affected by unevenness based on the first recess 11 of the substrate 10. For this reason, there is little variation in the wavelength and intensity of laser oscillation, and the resonator 42 with stable quality can be formed. As a result, the nitride semiconductor light emitting device 1 can be manufactured with a high yield.

The p-side electrode 130 is a positive electrode for supplying power to the nitride semiconductor layer 20. The p-side electrode 130 is laminated on the p-type contact layer 120 and the protective film 160, is in ohmic contact with the upper end surface of the p-type contact layer 120, and is further connected to the upper p-side pad electrode 140. . The p-side electrode 130 only needs to be in ohmic contact with the upper end surface of the p-type contact layer 120 and is not stacked on the protective film 160 but only on the upper end surface of the p-type contact layer 120. Also good.
The p-side electrode 130 can be formed, for example, by laminating a metal or alloy such as Ni or Au, or laminating these by sputtering or vapor deposition.

The p-side pad electrode 140 is an electrode pad that is connected to an external power source (not shown) by an Au wire (not shown) or the like and supplies power to the p-side electrode 130.
The p-side pad electrode 140 can be formed, for example, by laminating a metal or alloy such as Ni, Ti, or Au, or by laminating these using a sputtering method or a vapor deposition method.

The n-side electrode 150 is a negative electrode for supplying power to the nitride semiconductor layer 20. The n-side electrode 150 is formed on the back surface 10 b of the conductive substrate 10.
The n-side electrode 150 can be formed, for example, by laminating a metal or alloy such as V, Pt, Au, or the like by sputtering or vapor deposition.

The protective film 160 is an insulating protective film that covers the upper end surface of the nitride semiconductor layer 20 excluding the upper end surface of the p-type contact layer 120. The protective film 160 is formed by a sputtering method, a vapor deposition method, or the like using an insulating material such as SiO ₂ .

The protective film 170 is an insulating protective film that covers the side surfaces of the nitride semiconductor layer 20, and is formed using an insulating material such as SiO _{2 in the same} manner as the protective film 160.

  In the first embodiment, the nitride semiconductor layer 20 is configured by the n-type semiconductor layer on the substrate 10 (lower layer) side, but the p-type semiconductor layer may be configured on the substrate 10 side.

<Operation>
Next, the operation of the nitride semiconductor light emitting device (nitride semiconductor laser device) 1 in the first embodiment of the present invention will be described with reference to FIG.

  By applying a forward voltage to the nitride semiconductor layer 20 with the p-side electrode 130 (p-side pad electrode 140) as a positive electrode and the n-side electrode 150 as a negative electrode, the n-type cladding layer 60 to the n-type light guide layer 70 are applied. Then, electrons are injected into the active layer 80 via holes and holes are injected from the p-type cladding layer 110 into the active layer 80 via the p-type light guide layer 100 and the p-type cap layer 90. In the active layer 80, the injected electrons and holes recombine to generate light.

The light generated in the active layer 80 is confined in the resonator 42 due to the difference in the refractive index of each layer of the nitride semiconductor layer 20, and the reflection films provided on both end surfaces of the resonator 42 in the direction perpendicular to the plane of FIG. (Not shown) partly feeds back to contribute to laser oscillation. Inside the resonator 42, only light having a wavelength determined by the length of the resonator 42 or the like exists. A part of the light in the resonator 42 is emitted to the outside through a reflecting film formed as a half mirror on the resonator end surface on the near side in the direction perpendicular to the paper surface of FIG. . The emitted light is used for various purposes as laser light.
<Manufacturing method>
Next, a method for manufacturing the nitride semiconductor light-emitting element 1 according to the first embodiment of the present invention will be described with reference to FIG. 6 (see FIGS. 1 to 4 as appropriate).

  The manufacturing method of the nitride semiconductor light emitting device 1 according to the first embodiment includes a nitride semiconductor light emitting device 1 including a substrate 10 made of a nitride semiconductor and a nitride semiconductor layer 20 stacked on the surface 10a of the substrate 10. The first recess forming step, the second recess forming step, the first semiconductor layer forming step which is a lower layer portion of the nitride semiconductor layer 20 that does not include the active layer 80, and the nitride semiconductor layer 20 And a second semiconductor layer forming step which is an upper layer portion including the active layer 80.

  First, in the first recess forming step, the groove-shaped first recess 11 is formed on the surface 10a of the substrate 10, and in the second recess forming step, the bottom surface of the first recess 11 and the substrate 10 other than the first recess 11 are formed. A second concave portion 13 having a depth and an opening width smaller than those of the first concave portion 11 is formed in the first hill portion 12 which is the surface.

  Next, in the first semiconductor layer forming step, a recess 31 is formed at a position corresponding to the first recess 11 on the upper end surface 30a of the first semiconductor layer 30, and the second recess 13 is embedded to fill the first hill. The first semiconductor layer 30 is formed on the surface 10a of the substrate 10 on which the first recess 11 and the second recess 13 are formed so that the upper region of the portion 12 is planarized.

  Then, in the second semiconductor layer forming step, the second semiconductor is formed on the first semiconductor layer 30 so that the recess 41 is formed at a position corresponding to the first recess 11 on the upper end surface 40 a of the second semiconductor layer 40. Layer 40 is formed.

  A substrate is formed when the nitride semiconductor layer 20 is stacked by providing the first recess 11 and forming the nitride semiconductor layer 20 so that the recess 41 corresponding to the first recess 11 remains on the upper end surface 40 a of the nitride semiconductor layer 20. The strain caused by the difference in lattice constant between the nitride semiconductor layer 20 and the nitride semiconductor layer 20 is accumulated in the first recess 11, and as a result, the strain is divided in the first recess 11. As a result, the area in which the substrate 10 and the nitride semiconductor layer 20 are continuously in contact with each other while being distorted is reduced, so that the stress applied from the substrate 10 to the nitride semiconductor layer 20 in the upper region of the first hill portion 12 is reduced. Alleviated. In addition, since the second recess 13 is provided, the amount of rising edge growth generated at the edge of the first recess 11 is reduced, and the stress applied to the nitride semiconductor layer 20 from the substrate 10 is further relaxed. Further, since the second recess 13 is buried and flattened up to the upper end surface 30a of the first semiconductor layer 30, the active layer 80 included in the second semiconductor layer 40 is laminated flat.

By such a manufacturing method, the stress applied to the nitride semiconductor layer 20 from the substrate 10 is relieved and the generation of cracks in the nitride semiconductor layer 20 is reduced, so that the manufacturing yield is improved, and nitride semiconductor light emission due to the generation of cracks is achieved. A sudden loss of function of the element 1 can be prevented. Further, since the occurrence of edge growth is reduced, the processing accuracy of a device manufactured on the nitride semiconductor layer 20 can be improved, and the manufacturing yield can be improved. Furthermore, since the emission intensity and oscillation wavelength uniformity in the active layer 80 are good, the nitride semiconductor light emitting device 1 with stable quality can be manufactured. Moreover, since the critical film thickness with respect to a crack can be enlarged, the nitride semiconductor light-emitting element 1 can be manufactured using the nitride semiconductor with the high film thickness of the nitride semiconductor layer 20, or a high Al composition rate.
Hereinafter, each step will be described in detail.

(1st recessed part formation process)
First, in the first recess forming step, a substrate 10 made of a nitride semiconductor in which high dislocation density regions 10H and low dislocation density regions 10L as shown in FIG. The first recess 11 is formed as shown in FIG.
The first recess 11 is formed so as to include the high dislocation density region 10H so that its width W2 is wider than the width W3 of the high dislocation density region 10H (W2> W3).

  The substrate 10 having the first recess 11 on the surface 10a of the region having the high dislocation density region 10H is obtained by forming the first recess 11 after the substrate 10 is manufactured as in the first embodiment. Alternatively, the first recess 11 may be formed at the stage of manufacturing the substrate 10. Further, as the substrate 10, a low dislocation density nitride semiconductor substrate that does not have a commercially available high dislocation density region 10 </ b> H may be used.

When the first recess 11 is formed after the flat substrate 10 is manufactured as in the first embodiment, the method for forming the first recess 11 is not particularly limited. For example, a method of etching using a mask pattern corresponding to the first recess 11 or a high dislocation density using an etching selectivity between the low dislocation density region 10L and the high dislocation density region 10H without using the mask pattern. There is a method of forming the first recess 11 in the region 10H. Specifically, the high dislocation density region 10H is selected using the etching selectivity between the low dislocation density region 10L and the high dislocation density region 10H in BHF (buffered hydrofluoric acid), other acid solutions, dry etching, and the like. The first recess 11 can be formed by etching.
Since it can be divided along the first recess 11 in a later step, the cross-sectional shape of the first recess 11 should be a substantially trapezoid whose bottom is shorter than the top. ,preferable.

(Second recess forming step)
Next, as shown in FIG. 6 (c), in the second recess forming step, the first recess 11 is formed on the entire surface 10 a of the substrate 10, that is, on the bottom surface of the first recess 11 and the surface of the first hill 12. A smaller second recess 13 is formed.

Note that the order of the first recess forming step and the second recess forming step may be interchanged. First, after forming the second recess 13 on the surface 10a of the substrate 10, the first recess 11 is formed by etching. Thereby, since the first recess 11 is formed while maintaining the recess shape of the second recess 13, it is possible to manufacture the substrate 10 having the configuration in which the second recess 13 is disposed on the bottom surface of the first recess 11. it can.
Further, not only the second recess 13 but also a third recess (not shown) larger than the second recess 13 may be formed in the low dislocation density region 10L. The depth and width of the third recess are preferably formed in the same manner as the first recess 11. Similarly to the first recess 11, it is preferable to have the second recess 13 on the bottom surface of the third recess.
In this way, by substantially reducing the formation interval of the first recesses 11, the strain of the nitride semiconductor layer 20 stacked on the surface 10 a of the substrate 10 is reduced, and the nitride semiconductor layer 20 is applied from the substrate 10. The effect of relieving stress can be improved.

(First semiconductor layer forming step)
Next, as shown in FIG. 6D, in the first semiconductor layer forming step, the active layer of the nitride semiconductor layer 20 is formed on the surface 10a of the substrate 10 on which the first recess 11 and the second recess 13 are formed. A first semiconductor layer 30, which is a lower layer than 80, is formed.

  The formation method of the first semiconductor layer 30 is not particularly limited, but MOVPE (metal organic chemical vapor deposition), MOCVD (metal organic chemical vapor deposition), HVPE (hydride vapor deposition), MBE (molecular beam epitaxy). Any method known as a method for growing a nitride semiconductor can be suitably used. In particular, MOCVD is preferable because it can be grown with good crystallinity. The nitride semiconductor is preferably grown by appropriately selecting various nitride semiconductor growth methods depending on the purpose of use.

  The first semiconductor layer 30 is grown under conditions that allow it to grow laterally from the wall surfaces of the first recess 11 and the second recess 13 of the substrate 10. As such specific conditions, it is preferable to grow at a reduced pressure rather than normal pressure and at 1050 ° C. or higher.

The first semiconductor layer 30 is grown so that only the second recess 13 is planarized without planarizing the first recess 11. By forming the recess 31 at a position corresponding to the first recess 11 without flattening the first recess 11, the surface 10 a of the substrate 10 and the first semiconductor layer 30 are continuously in contact with each other while being distorted. Since the area that is being reduced is reduced, the stress applied to the first semiconductor layer 30 from the substrate 10 can be relaxed.
In addition, by providing the second recess 13 and embedding the second recess 13 with a nitride semiconductor material by lateral growth, distortion based on the difference in lattice constant between the substrate 10 and the first semiconductor layer 30 is also caused. This reduces the stress applied to the first semiconductor layer 30 from the substrate 10.

  Furthermore, by stacking the first semiconductor layer 30 on the surface 10a of the substrate 10 under conditions that allow easy growth in the lateral direction, the edge growth that can be formed above the edge portion of the first recess 11 can be reduced. By reducing the edge growth, the stress applied from the substrate 10 to the first semiconductor layer 30 is relaxed. Moreover, since the film thickness distribution of the nitride semiconductor layer 20 in the wafer surface is improved by reducing the edge growth, the adhesion of an etching mask or the like at the edge portion is improved. The processing accuracy of 1 is improved. For this reason, while suppressing generation | occurrence | production of a crack, the nitride semiconductor light-emitting device 1 can be produced with stable quality.

Further, the second recess 13 can be embedded and planarized in the underlayer 50, for example, or the planarization can be completed in the n-type cladding layer 60 and the n-type light guide layer 70.
Further, a crack prevention layer (not shown) may be formed between the base layer 50 and the n-type cladding layer 60. As the crack prevention layer, an In-containing nitride semiconductor represented by a general formula of In _x Ga _1-x N (0 <x ≦ 1) can be preferably used, acting as an in-plane buffer layer, Can be more effectively suppressed.

(Second semiconductor layer forming step)
Thereafter, as shown in FIG. 6E, the second semiconductor layer 40 is formed on the upper end surface 30 a of the first semiconductor layer 30 in the second semiconductor layer forming step. The second semiconductor layer 40 is a layer including the active layer 80.
Each layer constituting the second semiconductor layer 40 can be stacked by the same method as the first semiconductor layer 30.

  In the second semiconductor layer forming step, the recess 41 is preferably formed at a position corresponding to the recess 31 of the second semiconductor layer 40. Thereby, stress applied to each layer of the second semiconductor layer 40 including the active layer 80 from the substrate 10 through the first semiconductor layer 30 can be relaxed.

The second recess 13 is embedded in the first semiconductor layer 30, and each layer of the second semiconductor layer 40 including the active layer 80 is on a flat surface in the region above the first hill portion 12 of the substrate 10. It will be laminated.
For this reason, it is possible to reduce unevenness in the emission intensity in the plane of the active layer 80 of the second semiconductor layer 40, variation in the wavelength of laser oscillation in the resonator 42 formed by processing the second semiconductor layer 40, and the like. it can.

  Through the above manufacturing process, a nitride semiconductor multilayer structure in which the nitride semiconductor layer 20 is laminated on the surface 10a of the substrate 10 is formed.

(Light emitting element formation process)
Next, with reference to FIG. 4, the light emitting element formation process which forms the nitride semiconductor light emitting element 1 from the laminated structure of the nitride semiconductor mentioned above is demonstrated.

First, the nitride semiconductor layer 20 is etched in a region corresponding to the region above the first recess 11 of the substrate 10 to the middle of the base layer 50.
Next, the ridge structure is formed by etching the upper region from the middle of the p-type contact layer 120, the p-type cladding layer 110, and the p-type light guide layer 100, leaving the central portion in the horizontal direction in FIG.
Next, an insulating protective film 160 is formed on the upper end surface of the nitride semiconductor layer 20 excluding the upper end surface of the p-type contact layer 120 by sputtering or the like.
Then, the p-side electrode 130 made of a metal material is formed by sputtering or the like so as to contact the upper end surface of the p-type contact layer 120, that is, the upper end surface of the ridge structure.
Next, an insulating protective film 170 is formed on the side surface of the nitride semiconductor layer 20 exposed partway through the underlayer 50 by sputtering or the like.
Then, a p-side pad electrode 140 made of a metal material is formed on the p-side electrode 130 by sputtering or the like. Further, an n-side electrode 150 made of a metal material is formed on the back surface 10b side of the substrate 10 by sputtering or the like.

  Then, after performing a process such as alloying of the electrode by heat treatment, it is divided and / or cleaved into square or polygonal chips each having a side of about 150 to 1000 μm along the first recess 11, and the divided or cleaved surface A nitride semiconductor light-emitting device 1 is obtained by forming a reflection film (not shown) on the end face of the resonator 42 of FIG.

Second Embodiment
Next, referring to FIG. 7 (refer to FIGS. 1 and 4 as appropriate), the configuration of the substrate 10A in the second embodiment of the present invention will be described.

  The substrate 10A in the second embodiment shown in FIG. 7 is intermittently formed without extending in a specific direction, instead of the second recess 13 having a band-like opening, with respect to the substrate 10 of the first embodiment shown in FIG. The second concave portion 13A that is open automatically is formed in the entire region of the surface of the substrate 10A. In the example shown in FIG. 7, the opening shape of the second recess 13A is a regular hexagon.

  In the second embodiment, the second recess 13A is a bottomed hole in the shape of a regular hexagonal column having a regular hexagonal opening. The opening diameter and depth of the regular hexagonal second recess 13A can be equal to the width W5 and the depth D2 of the second recess 13 in the first embodiment shown in FIG.

  As in the case of using the substrate 10 shown in FIG. 1, a nitride semiconductor layer (not shown) is stacked on the substrate 10A on which the second recess 13A having an opening that is interrupted without extending in a specific direction is formed. By doing so, it is possible to prevent edge growth from occurring in the nitride semiconductor layer (not shown) in the region above the edge portion of the first recess 11 formed in the substrate 10A. As a result, it is possible to reduce the occurrence of cracks in the nitride semiconductor layer (not shown) and to process the nitride semiconductor layer (not shown) with stable accuracy because of good adhesion of resist and the like, with high yield. A nitride semiconductor light emitting device (not shown) can be manufactured.

  Further, the opening shape of the second recess 13A is not limited to a regular hexagon, and may be a triangle, a quadrangle, a polygon, a circle, or the like. Note that the intermittent opening without extending in a specific direction is not limited to a circle or a square, but also includes an ellipse, a rectangle, a parallelogram, and the like. This means that it does not include “sequentially extending over the entire area such as length and width”.

  In the example shown in FIG. 7, the plurality of second concave portions 13A are arranged so as to be regularly aligned with the square sides of the regular hexagon in the vertical direction. However, the present invention is not limited to this. It may be arranged densely in the length direction of the opening of the first recess 11 and sparsely arranged in the vertical direction. Further, it may be arranged randomly rather than regularly.

  Here, the surface of the substrate 10A is a C surface, and the second recess 13A has an M surface perpendicular to the vertical direction of the paper surface in FIG. 7, but the wall surface of the second recess 13A includes an M surface or an M surface. The surface is preferably formed so as to reduce the exposure of the surface having an angle close to the surface. In particular, it is more preferable to form a (11-20) plane (A plane, see FIG. 5) orthogonal to the M plane or a plane having an angle close to the A plane.

  On the other hand, when a horizontally long groove with many exposed M faces is formed as a small concave portion corresponding to the second concave portion 13A, it is effective in reducing edge growth at the edge portion of the first concave portion 11, An effect may not be obtained in suppressing the occurrence of cracks.

  Further, instead of the substrate 10 of the nitride semiconductor light emitting device 1 shown in FIG. 4, a nitride semiconductor light emitting device (not shown) can be configured using the substrate 10A in the second embodiment. Since the configuration other than the substrate 10A is the same as that of the nitride semiconductor light emitting device 1 shown in FIG. 4, the description of the configuration is omitted.

  The operation of the nitride semiconductor light emitting device (not shown) configured using the substrate 10A in the second embodiment shown in FIG. 7 is the same as that of the nitride semiconductor light emitting device 1 shown in FIGS. The description is omitted.

  The manufacturing method of the nitride semiconductor light emitting device (not shown) configured using the substrate 10A in the second embodiment shown in FIG. 7 is the same as that of the nitride semiconductor light emitting device 1 in the first embodiment shown in FIG. The method is the same as the second recess forming step shown in FIG. 6C except that a mask opened in a regular hexagon is used in place of the mask opened in a stripe pattern for forming the second recess 13. Since there is, explanation is omitted.

<Third Embodiment>
Next, with reference to FIG. 8, the nitride semiconductor light emitting devices 1B ₁ and 1B _{2 according to} the third embodiment of the present invention will be described.

In the first embodiment shown in FIG. 4, one nitride semiconductor light emitting element 1 is formed on one first hill portion 12 sandwiched between first recesses 11 provided on the substrate 10. In the third embodiment shown in FIG. 8, two nitride semiconductor light emitting devices ₁ </ _b > B ₁ , 1 </ _b > B ₂ are attached to _one first hill portion 12 sandwiched between first recesses 11 disposed on the substrate 10. To form.

The substrate 10 can be the same as that of the first embodiment, but the substrate 10 for each chip of the nitride semiconductor light emitting devices 1B ₁ , 1B ₂ is laterally sandwiched between the first recesses 11 in FIG. The direction is divided by using the first recess 11 and the intermediate region 12a of the first hill portion 12 as a cutting margin.

The substrate 10 has the strip-shaped first recesses 11 arranged in stripes at appropriate intervals so that the stress applied to the nitride semiconductor layer 20 stacked on the surface 10a from the substrate 10 is relieved. Use. A plurality of second recesses 13 are formed in the entire area of the surface 10 a of the substrate 10, that is, in the bottom surface of the first recess 11 and the surface of the first hill portion 12. Then, two nitride semiconductors are formed for each first hill portion 12 from a laminated structure of nitride semiconductors stacked on the first hill portion 12 sandwiched between the first recesses 11 and the stress applied from the substrate 10 being relaxed. Light emitting elements 1B ₁ and 1B ₂ are formed. Accordingly, it is possible to reduce the area of the first recess 11 in the wafer which is the source of the substrate 10, the number of chip nitride semiconductor are formed light-emitting element 1B _1, 1B ₂ per wafer can be increased.
Since the other configuration is the same as that of the nitride semiconductor light emitting device 1 of the first embodiment shown in FIG. 4, detailed description of the configuration is omitted.

The operations of the nitride semiconductor light emitting devices 1B ₁ and 1B ₂ in the third embodiment shown in FIG. 8 are the same as those of the nitride semiconductor light emitting device 1 in the first embodiment shown in FIG. .

Next, a method for manufacturing the nitride semiconductor light emitting devices 1B ₁ and 1B _{2 according} to the third embodiment shown in FIG. 8 will be described.
In the method for manufacturing the nitride semiconductor light emitting devices 1B ₁ and 1B _{2 according to} the third embodiment, the process up to the step of producing a nitride semiconductor laminated structure in which the nitride semiconductor layer 20 is laminated on the surface 10a of the substrate 10 (first concave portion) Since the formation process to the second semiconductor layer formation process are the same as the manufacturing method of the nitride semiconductor light emitting device 1 of the first embodiment shown in FIG. 6, the description of these processes is omitted.

Next, with reference to FIG. 8, a stacked structure of a nitride semiconductor, it is described light-emitting element forming step of forming a nitride semiconductor light emitting device 1B _1, 1B _2.

  First, with respect to the nitride semiconductor layer 20, the region corresponding to the region above the first recess 11 of the substrate 10 and the region including the intermediate region 12 a serving as a cutting allowance in the first hill portion 12 are partway through the foundation layer 50. Etch.

  Next, a step of forming a ridge structure in the upper region from the middle of the p-type contact layer 120, the p-type cladding layer 110, and the p-type light guide layer 100, and the nitride semiconductor layer 20 excluding the upper end surface of the p-type contact layer 120 A step of forming an insulating protective film 160 on the upper end surface, a step of forming a p-side electrode 130 so as to be in contact with the upper end surface of the p-type contact layer 120, and the nitride semiconductor layer 20 exposed partway through the underlayer 50. The step of forming the insulating protective film 170 on the side surface, the step of forming the p-side pad electrode 140 on the p-side electrode 130, and the step of forming the n-side electrode 150 on the back surface 10b side of the substrate 10 are the first step. Since it is the same as that of embodiment, detailed description is abbreviate | omitted.

Then, after performing a process such as alloying of the electrode by heat treatment, it is divided and / or cleaved into quadrangular or polygonal chips along the intermediate region 12a of the first concave portion 11 and the first hill portion 12. Alternatively, a reflective film (not shown) is formed on the end face of the resonator 42 portion of the cleavage plane, so that the nitride semiconductor light emitting devices 1B ₁ and 1B ₂ are obtained.

In the third embodiment, two nitride semiconductor light emitting devices 1B ₁ and 1B ₂ are formed in one first hill portion 12 sandwiched between the first recesses 11 disposed on the substrate 10. However, the present invention is not limited to this, and three or more nitride semiconductor light emitting elements can be formed in one first hill portion 12 sandwiched between the first recesses 11.
In addition, the second recess 13 formed in the substrate 10 is not limited to a recess having a groove, that is, a strip-shaped opening, and instead of the second recess 13, the second recess 13 has an opening such as a regular hexagon in the second embodiment. The second recess 13A may be formed.

<Fourth embodiment>
Next, with reference to FIG. 9 (refer to FIG. 1 as appropriate), the structure of the nitride semiconductor light emitting device 1C according to the fourth embodiment of the present invention will be described. The nitride semiconductor light emitting elements ₁ , 1B ₁ , 1B _{2 and the} like of the _{first to} third embodiments are configured as laser elements, but the nitride semiconductor light emitting element 1C of the fourth embodiment is an LED (light emitting diode) element. It is the composition.

<Configuration>
In the nitride semiconductor light emitting device 1C of the fourth embodiment shown in FIG. 9, a nitride semiconductor layer 20C composed of a first semiconductor layer 30C and a second semiconductor layer 40C is stacked on a surface 10a of a substrate 10 composed of a nitride semiconductor. ing. The first semiconductor layer 30C includes a base layer (first n-type semiconductor layer) 50C and an n-type contact layer (second n-type semiconductor layer) 180. The second semiconductor layer 40C includes the active layer 80 and the p-type. It consists of a semiconductor layer 190.

  The upper end surface of the nitride semiconductor layer 20C (the upper end surface of the p-type semiconductor layer 190) is in ohmic contact with the p-side electrode 130C, and the p-side electrode 130C is electrically connected to the p-side pad electrode 140C. A recess 21 is provided in a part of the upper end surface of the nitride semiconductor layer 20 </ b> C, and the bottom surface of the recess 21 is an exposed surface 180 a of the n-type contact layer 180. An n-side electrode 150C is provided on the exposed surface 180a of the n-type contact layer 180, and the n-side electrode 150C and the n-type contact layer 180 are in ohmic contact.

Next, the configuration of each unit will be described.
The substrate 10 in the fourth embodiment can be the same as the substrate 10 in the first to third embodiments. The substrate 10 in the fourth embodiment shown in FIG. 9 is divided along the intermediate region 12a (see FIG. 8) of the first recess 11 and the first hill portion 12 in the same manner as the substrate 10 in the third embodiment. Is.

  The first semiconductor layer 30 </ b> C is an n-type semiconductor layer including the base layer 50 </ b> C and the n-type contact layer 180.

In the fourth embodiment, the second recess 13 is embedded in the base layer 50C, and the upper end surface of the base layer 50C in the upper region of the first hill portion 12 is flattened. An example of the underlayer 50C is Al _a Ga _1-a N (0 ≦ a ≦ 1). The underlayer 50 may also be used as the n-type contact layer 180.

The n-type contact layer 180 is a layer that receives power supplied from the n-side electrode 150 </ b> C that is in ohmic contact and injects electrons into the active layer 80.
The n-type contact layer 180 includes, for example, a GaN layer doped with Si as an n-type impurity, an n-type contact layer made of Si-doped GaN, and an n-type cladding layer made of n-type AlGaN in this order. It can be a layered structure. Further, the n-type cladding layer in the case of a two-layer structure can be configured using the same material as that of the n-type cladding layer 60 in the first embodiment shown in FIG.

  The n-type contact layer 180 may also be used as the base layer 50C. In this case, the second recess 13 is embedded in the n-type contact layer 180, and the upper end surface in the upper region of the first hill portion 12, that is, the upper end surface of the first semiconductor layer 30C may be flat. .

The active layer 80 is a layer that generates light through recombination of electrons injected from the n-type contact layer 180 and holes injected from the p-type semiconductor layer 190. The active layer 80 is stacked on the first semiconductor layer 30 </ b> C that is flattened by embedding the second recess 13. For this reason, unevenness of the emission intensity in the plane of the active layer 80 is reduced.
Since the active layer 80 can have the same configuration as the active layer 80 in the first embodiment, a detailed description thereof is omitted.

The p-type semiconductor layer 190 is a layer whose upper end surface is in ohmic contact with the p-side electrode 130 </ b> C, receives power supplied from the p-side electrode 130 </ b> C, and injects holes into the active layer 80.
The p-type semiconductor layer 190 is, for example, a laminate of a GaN doped with Mg as a p-type impurity, an n-type cladding layer made of n-type AlGaN, and a p-type contact layer made of GaN doped with Mg in this order. It can be a layered structure. Further, the p-type cladding layer and the p-type contact layer in the case of the two-layer structure are configured using the same materials as the p-type cladding layer 110 and the p-type contact layer 120 in the first embodiment shown in FIG. You can also

  The p-side electrode 130C is a positive electrode for supplying power to the nitride semiconductor layer 20C. The p-side electrode 130C is a translucent full-surface electrode that is in ohmic contact with almost the entire region of the upper end surface of the p-type semiconductor layer 190, and a p-side pad electrode 140C provided on a part of the upper end surface of the p-side electrode 130C. And are electrically connected.

Since the nitride semiconductor light emitting device 1C of the fourth embodiment is configured to extract light also from the electrode arrangement surface side, the p-side electrode 130C has translucency at the wavelength of light emitted from the active layer 80. Is preferred. Examples of materials having both translucency and conductivity include, for example, ITO (indium tin oxide), ZnO, a metal thin film in which Ni and Au are stacked in this order from the p-type semiconductor layer 190 side, Ag, Ni, Au, and the like. A thin film of these metals or an alloy thereof can be used.
The p-side electrode 130C can be formed by stacking the above-described materials by, for example, a sputtering method or a vapor deposition method.

The p-side pad electrode 140C is provided on a part of the upper end surface of the p-side electrode 130C, is connected to an external power source (not shown) by an Au wire (not shown), etc., and supplies power to the p-side electrode 130C. It is an electrode pad for.
The p-side pad electrode 140C can be configured using the same material as the p-side pad electrode 140 in the first embodiment shown in FIG.

The n-side electrode 150C is a negative electrode for supplying power to the nitride semiconductor layer 20C. The n-side electrode 150 </ b> C is formed on the exposed surface 180 a of the n-type contact layer 180 and is in ohmic contact with the n-type contact layer 180.
The n-side electrode 150C can be configured using the same material as the n-side electrode 150 in the first embodiment shown in FIG.

  Further, like the nitride semiconductor light emitting device 1 in the first embodiment shown in FIG. 4, the upper end surface and side surfaces of the nitride semiconductor light emitting device 1C excluding the p-side pad electrode 140C and the n-side electrode 150C are insulated. You may make it coat | cover with a protective film.

  In addition, the configuration of the nitride semiconductor light emitting device 1C is sufficient if the second recess 13 is embedded and planarized at least on the upper end surface of the first semiconductor layer 30C on which the active layer 80 is stacked. Other light emitting diode element configurations such as a layer configuration of the layer 20C and electrode arrangement may be employed.

<Operation>
Next, the operation of the nitride semiconductor light emitting device (nitride semiconductor light emitting diode device) 1C according to the fourth embodiment of the present invention will be described with reference to FIG.

  By applying a forward voltage to the nitride semiconductor layer 20C using the p-side electrode 130C (p-side pad electrode 140C) as a positive electrode and the n-side electrode 150C as a negative electrode, electrons are transferred from the n-type contact layer 180 to the active layer 80. While being injected, holes are injected from the p-type semiconductor layer 190 into the active layer 80. In the active layer 80, the injected electrons and holes recombine to generate light.

  The light generated in the active layer 80 passes through the nitride semiconductor layer 20C, the translucent p-side electrode 130C, and the substrate 10, and is extracted outside the nitride semiconductor light emitting device 1C.

<Manufacturing method>
Next, with reference to FIG. 9, a method for manufacturing the nitride semiconductor light emitting device 1C in the fourth embodiment will be described.
In the method for manufacturing the nitride semiconductor light emitting device 1C according to the fourth embodiment, the manufacturing process until the nitride semiconductor multilayer structure is formed on the substrate 10 uses the material constituting each layer of the nitride semiconductor layer 20C. Thus, the manufacturing process can be the same as that of the first embodiment shown in FIG.

  At this time, the first semiconductor layer 30C is grown so that only the second recess 13 is planarized without planarizing the first recess 11. That is, the recess 31 (see FIG. 6) is formed at a position corresponding to the first recess 11 without flattening the first recess 11. In addition, the second semiconductor layer 40C is preferably grown such that a recess 41 (see FIG. 6) is formed at a position corresponding to the recess 31 (see FIG. 6) of the first semiconductor layer 30C.

  Next, in the light emitting element forming step, a p-side electrode 130C made of a light-transmitting conductive material such as ITO is formed on the upper end surface of the nitride semiconductor layer 20C by sputtering or the like.

  Subsequently, in the nitride semiconductor layer 20C including the layer of the p-side electrode 130C, the region corresponding to the upper region of the first recess 11 of the substrate 10 and the first hill portion 12 are formed as in the third embodiment. The intermediate region 12a (see FIG. 8) is etched partway through the underlayer 50C. Further, in order to form the n-side electrode 150C for the nitride semiconductor layer 20C, a part of the nitride semiconductor layer 20C is etched until the n-type contact layer 180 is exposed.

Next, an n-side electrode 150C made of a metal material is formed on the exposed surface 180a of the n-type contact layer 180 by sputtering or the like. Further, a p-side pad electrode 140C made of a metal material is formed on a part of the p-side electrode 130C by sputtering or the like.
When the same material is used for the p-side pad electrode 140C and the n-side electrode 150C, these may be formed in the same process.

  Then, after performing a process such as alloying of the electrode by heat treatment, a rectangular or polygonal shape having a side of about 150 to 1000 μm along the intermediate region 12a (see FIG. 8) of the first concave portion 11 and the first hill portion 12. By dividing and / or cleaving the chip, a nitride semiconductor light emitting device 1C is obtained.

Next, examples and comparative examples for confirming the effects of the present invention will be described with reference to FIGS. 1 and 4 as appropriate.
Example 1
In this example, a laminated structure in which the nitride semiconductor layer 20 having the configuration shown in FIG. 4 is laminated on the substrate 10 using the substrate 10 shown in FIG. 1 is manufactured by the following method.
As the substrate 10, a GaN substrate having a C-plane as a main surface (surface 10a) and alternately having high dislocation density regions 10H and low dislocation density regions 10L is used.

First, the first recess 11 is formed in the surface 10 a of the substrate 10. Then, a mask made of SiO ₂ is patterned on the low dislocation density region 10L corresponding to the first hill portion 12. At this time, a region including the high dislocation density region 10H is an opening of the mask. Thereafter, etching is performed by RIE (reactive ion etching) using Cl ₂ gas to form a first recess 11 having a width W2 of 60 μm and a depth D1 of 2.4 μm. Next, a second recess 13 smaller than the first recess 11 is formed in the same manner as the first recess 11 on the bottom surface of the first recess 11 and the surface of the first hill portion 12 which is the low dislocation density region 10L. The width W5 of the second recess 13 is 3 μm, and the width W4 of the second hill portion 14 that is the interval between the adjacent second recesses 13 is 3 μm. The depth D2 is 0.4 μm. Both the first concave portion 11 and the second concave portion 13 are formed by arranging stripes extending in the direction in which the opening is perpendicular to the M-plane. That is, the A surface is exposed on the wall surfaces of the first concave portion 11 and the second concave portion 13 arranged in stripes, and the M surface is not exposed. Further, the C surface is exposed on the bottom surfaces of the first recess 11 and the second recess 13. The substrate 10 on which the first recess 11 and the second recess 13 are formed is transported to the MOCVD apparatus, and the nitride semiconductor layer 20 is formed.

First, a base layer 50 made of Si-containing Al _0.02 Ga _0.98 N is grown as a first n-type semiconductor layer on the substrate 10 to a thickness of 2.0 μm.

A crack prevention layer (not shown) made of Si-containing In _0.05 Ga _0.95 N is grown as a second n-type semiconductor layer on the underlayer 50 to a thickness of 0.15 μm.

An n-type cladding layer 60 made of Si-containing Al _0.11 Ga _0.89 N is grown to a thickness of 1.0 μm as a third n-type semiconductor layer on the crack prevention layer (not shown).

Next, an n-type light guide layer 70 made of undoped Al _0.05 Ga _0.95 N is grown as a fourth n-type semiconductor layer on the n-type cladding layer 60 to a thickness of 0.14 μm.

An active layer 80 having a three-layer structure is formed on the n-type light guide layer 70. In the active layer 80, first, a barrier layer made of Si-containing Al _0.11 Ga _0.89 N is grown to a thickness of 105 mm. Subsequently, a well layer made of undoped GaN is grown to a thickness of 175 mm. Finally, a barrier layer made of undoped Al _0.11 Ga _0.89 N is grown to a thickness of 75 mm to form an active layer 80 having a single quantum well structure (SQW) having a thickness of 355 mm.

A p-type cap layer 90 made of Mg-containing Al _0.20 Ga _0.80 N is grown as a first p-type semiconductor layer on the active layer 80 to a thickness of 130 Å.

A p-type light guide layer 100 made of undoped Al _0.05 Ga _0.95 N is grown as a second p-type semiconductor layer on the p-type cap layer 90 to a thickness of 0.15 μm.

A p-type cladding layer 110 is formed on the p-type light guide layer 100 as a third p-type semiconductor layer. In the p-type cladding layer 110, first, an A layer made of undoped Al _0.14 Ga _0.86 N is grown to a thickness of 80 mm, and then Mg-doped Al _0.06 Ga _0.94 N is made thereon. The B layer is grown to a thickness of 80 mm. This is repeated 28 times, and the A layer and the B layer are alternately laminated to form a multilayer film (superlattice structure) having a layer thickness of 0.45 μm.

Finally, a p-type contact layer 120 made of Mg-doped GaN is grown on the p-type cladding layer 110 as a fourth p-type semiconductor layer to a thickness of 150 mm.
As described above, a stacked structure in which the nitride semiconductor layer 20 is grown on the substrate 10 is formed.

(Example 2)
As Example 2, a stacked structure of the nitride semiconductor layer 20 is produced using the substrate 10A shown in FIG. The second recess 13A having a regular hexagonal opening in the substrate 10A has a regular hexagonal side length of 3 μm and a depth of 0.4 μm, and an interval between adjacent second recesses 13A of 2 μm.
The substrate is manufactured in the same manner as in Example 1 except for the difference in the shape of the second recess 13A of the substrate 10A.

(Comparative Example 1)
As a comparative example 1, a laminated structure of the nitride semiconductor layer 20 is manufactured using a substrate in the related art in which the second recess 13 is not formed instead of the substrate 10 in the first embodiment. The substrate is manufactured in the same manner as in Example 1 except for the difference in substrate.

(Experimental result)
With respect to the laminated structures of the above-described examples and comparative examples, the nitride semiconductor layer 20 was observed with an optical microscope, and the results of counting the number of cracks in a range of 20 mm long × 500 μm wide are shown below. However, the number of cracks is shown as a percentage based on the case of Comparative Example 1 which is a conventional technique.
Example 1 62%
Example 2 77%
Comparative Example 1 100%

As shown in the experimental results, the occurrence of cracks is suppressed in Example 1 and Example 2 as compared to Comparative Example 1 which is a conventional technique.
Further, by manufacturing a nitride semiconductor light emitting element (nitride semiconductor laser element) using the stacked structure of Example 1 and Example 2, a highly reliable device can be obtained.

(Example 3)
Further, as an example of the fourth embodiment shown in FIG. 9, a nitride semiconductor light emitting device (nitride semiconductor light emitting diode device) is manufactured.

In Example 3, an AlN substrate made of a low dislocation density nitride semiconductor that does not have a high dislocation density region where dislocation defects are concentrated is used as the substrate 10. First, a 4 μm-thick underlayer 50C made of undoped GaN is formed as a first n-type semiconductor layer on the surface 10a of the substrate 10 manufactured in the same manner as in Example 1.
Next, as the second n-type semiconductor layer, an n-type contact layer 180 having a thickness of about 2 μm made of Si-containing Al _0.07 Ga _0.93 N is formed.

Next, as the active layer 80, a barrier layer made of Si-doped Al _0.1 Ga _0.9 N and a well layer made of undoped In _0.05 Ga _0.95 N are used as the first barrier layer / First well layer / second barrier layer / second well layer / third barrier layer / third well layer / fourth barrier layer / fourth well layer / fifth barrier layer / fifth well layer / sixth barrier layer Laminate in order. At this time, the first barrier layer to the fifth barrier layer are formed with a thickness of 200 mm, the sixth barrier layer with a thickness of 400 mm, and the first well layer to the fifth well layer with a thickness of 150 mm. However, only the sixth barrier layer is made of undoped Al _0.1 Ga _0.9 N.

Further, the p-type semiconductor layer 190 has a three-layer structure and is sequentially stacked on the active layer 80.
First, as a first p-type semiconductor layer, a p-type cladding layer having a thickness of 220 mm made of Mg-doped Al _0.3 Ga _0.7 N is formed.
Next, a first p-type contact layer made of Al _0.07 Ga _0.93 N and having a thickness of 0.1 μm is formed as the second p-type semiconductor layer.
Then, a 0.02 μm-thick second p-type contact layer made of Mg-doped Al _0.07 Ga _0.93 N is formed as the third p-type semiconductor layer.
As described above, a stacked structure in which the nitride semiconductor layer 20C is grown on the substrate 10 is formed. Thereafter, a part of the nitride semiconductor multilayer structure including the layer of the p-side electrode 130 </ b> C is etched to expose the n-type contact layer 180.

A p-side electrode 130C made of Ni, Ag, Ti, or Pt is formed on the second p-type contact layer.
Then, the p-side pad electrode 140C and the n-side electrode 150C are formed of a metal material on the p-side electrode 130C and the exposed surface 180a of the n-type contact layer 180, respectively.

Further, an insulating protective film made of SiO ₂ is formed on the exposed surface of the nitride semiconductor light emitting device 1C other than the p-side pad electrode 140C and the n-side electrode 150C.

  Thereafter, the element is divided by dicing to obtain a nitride semiconductor light emitting element 1C having a size of about 1 mm × about 1 mm.

  As shown in Example 3, a nitride semiconductor light-emitting element 1C having a light-emitting diode element configuration is manufactured using the substrate 10 provided with the first concave portion 11 and the second concave portion 13, whereby a highly reliable device and can do.

  As described above, according to the present invention, by providing the second recess in the nitride semiconductor substrate, edge growth occurs in the nitride semiconductor layer stacked on the substrate, compared to the case where only the first recess is provided. Is reduced, and stress applied to the nitride semiconductor layer from the substrate is relieved. For this reason, the generation of cracks can be reduced, the processing accuracy is improved, and a nitride semiconductor light emitting device that operates stably can be manufactured.

The nitride semiconductor light emitting device according to the present invention can be used as an optical disk light source, a display light source, an exposure light source, and the like.
Further, as a nitride semiconductor laser element, which is one of the embodiments of the nitride semiconductor light emitting element of the present invention, a diffraction grating is provided inside for feedback, in addition to the one having a Fabry-Perot resonator that feeds back at the end face. The present invention can be applied to a device having a DBR (Distributed Bragg Reflector).

₁ , 1B ₁ , 1B ₂ , 1C Nitride semiconductor light emitting device 10, 10A Substrate 10H High dislocation density region 10L Low dislocation density region 12 First hill (convex portion)
13, 13A Second recessed portion 14, 14A Second hill portion 20, 20C Nitride semiconductor layer 30, 30C First semiconductor layer 30a Upper end surface 31 Recessed portion 40, 40C Second semiconductor layer 40a Upper end surface 41 Recessed portion 42 Resonator 50, 50C Underlayer 60 n-type cladding layer 70 n-type light guide layer 80 active layer 90 p-type cap layer 100 p-type light guide layer 110 p-type cladding layer 120 p-type contact layer 130, 130C p-side electrode 140, 140C p-side pad electrode 150, 150C n-side electrode 160 protective film 170 protective film 180 n-type contact layer 190 p-type semiconductor layer

Claims (13)

A nitride semiconductor light emitting device comprising a substrate made of a nitride semiconductor and a nitride semiconductor layer laminated on the surface of the substrate,
A band-shaped first recess formed on the surface of the substrate;
A plurality of second concave portions formed on the bottom surface of the first concave portion and the convex portion which is the surface of the substrate other than the first concave portion;
The nitride semiconductor layer includes a first semiconductor layer stacked on a surface of the substrate;
A second semiconductor layer having at least an active layer stacked on the first semiconductor layer,
The first semiconductor layer is stacked such that a recess is formed at a position corresponding to the first recess on an upper end surface of the first semiconductor layer;
A nitride semiconductor light emitting device characterized by the above.   The nitride semiconductor light emitting device according to claim 1, wherein the first semiconductor layer includes a plurality of nitride semiconductor layers.   3. The nitride semiconductor light emitting device according to claim 1, wherein an upper end surface of the first semiconductor layer in a region above the convex portion is flattened. 4.   4. The nitride semiconductor light-emitting device according to claim 1, wherein the plurality of second recesses have openings extending in parallel with an extending direction of the belt-shaped first recess. 5. element.   4. The nitride semiconductor light emitting element according to claim 1, wherein the plurality of second recesses have openings that are intermittently extended without extending in a specific direction. 5. The substrate has a high dislocation density region having a relatively high dislocation defect density, and a low dislocation density region having a dislocation defect density lower than that of the high dislocation density region,
6. The nitride semiconductor light emitting device according to claim 1, wherein the first recess is provided in a region including the high dislocation density region.   The surface of the substrate is a C-plane of the nitride semiconductor, and the extending direction of the strip-shaped first recess is perpendicular to the M-plane of the nitride semiconductor. The nitride semiconductor light-emitting device according to claim 1.   The nitride semiconductor light emitting device according to claim 7, wherein a wall surface of the second recess is a surface that is not parallel to the M-plane of the nitride semiconductor.   9. The nitride semiconductor light emitting device according to claim 1, wherein the first semiconductor layer includes a nitride semiconductor containing aluminum.   The nitride semiconductor light emitting device according to claim 9, wherein the second recess is filled with a nitride semiconductor containing the aluminum of the first semiconductor layer.   11. The first semiconductor layer according to claim 1, wherein the second semiconductor layer is laminated so that a recess is formed at a position corresponding to the first recess on an upper end surface of the second semiconductor layer. The nitride semiconductor light-emitting device according to claim 1.   The nitride semiconductor light emitting device according to claim 11, wherein the nitride semiconductor light emitting device is divided along the recess formed in an upper end surface of the second semiconductor layer.   13. The nitride semiconductor light emitting element according to claim 1, wherein the second semiconductor layer has a resonator for laser oscillation in a region above the convex portion.

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