JP2009135284A - Semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser element capable of improving a performance, and method of manufacturing the same. <P>SOLUTION: The semiconductor laser element 1 includes a photonic crystal layer 7 and an active layer 5. The photonic crystal layer 7 includes a high refractive index part 71 and a low refractive index part 72 having a refractive index lower than the refractive index of the high refractive index part 71. The active layer 5 is formed on one main surface side of the photonic crystal layer 7 and emits light by injecting a carrier. Each of the high refractive index part 71 and the low refractive index part 72 includes GaN. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device and a manufacturing method thereof, and more particularly to a semiconductor laser device including a two-dimensional diffraction grating and a manufacturing method thereof.

  In recent years, a photonic crystal laser using a photonic crystal as a two-dimensional diffraction grating has been developed. According to this photonic crystal laser, two-dimensional single-mode oscillation can be realized by diffracting light in various directions existing in the photonic crystal plane to generate a standing wave. Luminous efficiency can be improved compared to a three-dimensional DFB laser or the like. In addition, since this photonic crystal laser has a feature of emitting light in a direction perpendicular to the main surface of the photonic crystal, the output of the laser light can be increased. As an example of a photonic crystal laser, for example, Japanese Laid-Open Patent Publication No. 2000-332351 (Patent Document 1) discloses a semiconductor light emitting device having a two-dimensional diffraction grating of a photonic crystal layer.

  This semiconductor light emitting device includes a substrate, a two-dimensional diffraction grating that is a photonic crystal layer, an n-type confinement layer, an active layer, a p-type confinement layer, an anode electrode, and a cathode electrode. A two-dimensional diffraction grating is formed on a substrate made of InP. On the two-dimensional diffraction grating, an n-type confinement layer made of InP, an active layer having a multiple quantum well structure made of InGaAs / InGaAsP, and an InP The p-type confinement layers are stacked in this order. A circular anode electrode is formed on the upper surface of the p-type confinement layer, and a cathode electrode is formed on the lower surface of the substrate. The two-dimensional diffraction grating has a high refractive index portion made of InP or the like and a low refractive index portion. The low refractive index portion is created by periodically forming a plurality of holes on the surface of the high refractive index portion. When the hole is not filled (space), the low refractive index portion is made of air, and when the hole is filled, the low refractive index portion is made of a silicon nitride film or the like.

  The semiconductor light emitting device of Patent Document 1 is manufactured by the following method. First, a first component having a two-dimensional diffraction grating formed on a first substrate, a p-type confinement layer, an active layer, and an n-type confinement layer are formed in this order on the second substrate. A second part of the same shape is produced. Next, the second component is turned upside down, the photonic crystal of the first component and the n-type confinement layer of the second component are fusion bonded, and then the second substrate is removed. Thereafter, an anode electrode and a cathode electrode are formed.

  However, when forming a GaN-based photonic crystal laser, the manufacturing method of Patent Document 1 has a problem that it is difficult to perform fusion bonding. This is due to the low flatness of the GaN crystal surface. In view of this, International Publication No. 2006/062084 pamphlet (Patent Document 2) proposes a photonic crystal laser manufacturing method that does not require fusion bonding.

  In the manufacturing method of Patent Document 2, first, an n-type cladding layer, an active layer, a p-type cladding layer, and a photonic crystal layer are grown on the upper surface of the substrate in this order. This photonic crystal layer includes an epitaxial layer made of GaN and a low refractive index portion. Then, a layer containing a GaN component is epitaxially grown (regrown) on the epitaxial layer and grown in a direction along the upper surface of the substrate in a region immediately above the low refractive index portion. Thereafter, a layer above the photonic crystal layer is formed.

Patent Document 2 mentions that SiO ₂ , MgF ₂ , CaF ₂ , BaF ₂ , LiF, or the like is used in addition to the case where air is used as the low refractive index portion. When air is used, a plurality of holes periodically formed on the surface of the epitaxial layer are used as they are. When a material such as SiO ₂ other than air is used, a material such as SiO ₂ is used in the holes. Is formed. Furthermore, it is also described that a low refractive index portion is formed by both air and a material such as SiO ₂ by forming a material such as SiO ₂ only at the bottom of the hole.
JP 2000-332351 A International Publication No. 2006/062084 Pamphlet

  As described above, in the method described in Patent Document 2, a plurality of holes are formed on the surface of the epitaxial layer made of GaN, and air (air holes) in these holes is used as the low refractive index portion of the two-dimensional diffraction grating. ing. However, since it is difficult to form air holes in a uniform shape, it is difficult to form a two-dimensional diffraction grating with high accuracy. That is, the epitaxial growth of GaN has unique properties such as a very high migration rate. If the surface of the epitaxial layer made of GaN or the side wall of the hole is disturbed, the growth of GaN is promoted at that point, and the inside of the hole may be partially filled with GaN. As a result, the two-dimensional diffraction grating cannot be formed with high accuracy, which hinders improvement in performance of the semiconductor laser element.

Further, as described above, in the method described in Patent Document 2, a plurality of holes are formed on the surface of the epitaxial layer made of GaN, and low refractive index portions such as SiO ₂ are formed in these holes. However, in the case of forming a material such as SiO _2, the material, such as SiO ₂ there is adverse effect to other layers such as the active layer. That is, the thermal expansion coefficient of a material such as SiO ₂ described in Patent Document 2 is significantly different from the thermal expansion coefficient of GaN. For this reason, when the layer containing the GaN component is epitaxially grown on the two-dimensional diffraction grating, if the two-dimensional diffraction grating is kept at a high temperature (for example, about 1000 ° C.), the stress and strain caused by the heat are generated in the two-dimensional diffraction grating. There was a risk of occurrence. As a result, the light emission characteristics of the light emitting layer are deteriorated, which hinders improvement in performance of the semiconductor laser device.

In addition, when a low refractive index portion such as SiO ₂ is formed in the hole, there is a possibility that an element (for example, silicon) constituting the material such as SiO ₂ may diffuse into the nearby layer. As a result, the improvement of the reliability of the semiconductor laser element has been hindered.

  Accordingly, an object of the present invention is to provide a semiconductor laser device capable of improving performance and a method for manufacturing the same.

  Another object of the present invention is to provide a semiconductor laser device capable of improving reliability and a method for manufacturing the same.

  The semiconductor laser device in the present invention includes a two-dimensional diffraction grating and a light emitting layer. The two-dimensional diffraction grating has a high refractive index portion and a low refractive index portion having a refractive index lower than that of the high refractive index portion. The light emitting layer is formed on one main surface side of the two-dimensional diffraction grating, and emits light when carriers are injected. Each of the high refractive index portion and the low refractive index portion includes a gallium nitride (GaN) component.

  The method for manufacturing a semiconductor laser device of the present invention includes the following steps. A two-dimensional diffraction grating having a high refractive index portion and a low refractive index portion having a refractive index lower than that of the high refractive index portion is formed. A light emitting layer that emits light when carriers are injected is formed on one main surface side of the two-dimensional diffraction grating. Each of the high refractive index portion and the low refractive index portion includes a GaN component.

  According to the semiconductor laser device and the manufacturing method thereof of the present invention, the low refractive index portion of the two-dimensional diffraction grating is filled with a material containing a GaN component instead of an air hole. Even if the surface or the side wall is disturbed, the high refractive index portion or the low refractive index portion does not grow abnormally from that portion. For this reason, a two-dimensional diffraction grating can be formed with higher precision than in the case of air holes. In addition, since the high refractive index portion and the low refractive index portion are similar in composition and physical properties, stress and strain due to heat hardly occur in the two-dimensional diffraction grating. As a result, the performance of the semiconductor laser element can be improved.

  In addition, since the high refractive index portion and the low refractive index portion are similar in composition and physical properties, even if the elements constituting the low refractive index portion diffuse into the high refractive index portion, the influence is small. For this reason, the reliability of the semiconductor laser element can be improved.

  In the semiconductor laser device of the present invention, the difference between the refractive index of the high refractive index portion and the refractive index of the low refractive index portion is preferably 0.04 or more. As a result, the light incident on the two-dimensional diffraction grating is easily diffracted at the lattice points, so that standing waves are easily generated between the lattice points.

In the semiconductor laser device of the present invention, preferably, each of the high refractive index portion and the low refractive index portion is In _y Ga _1-y N (0 ≦ y <1) or Al _x Ga _1-x N (0 ≦ x <1). ). Since these materials are particularly similar to each other in physical properties, they are suitable as materials for a high refractive index portion and a low refractive index portion.

In the semiconductor laser device of the present invention, preferably, the high refractive index portion is made of In _y Ga _1-y N (0 ≦ y ≦ 0.15), and the low refractive index portion is made of Al _x Ga _1-x N ( 0 ≦ x ≦ 0.5). Since these materials have particularly close lattice constants, the lattice mismatch between the high refractive index portion and the low refractive index portion can be alleviated.

  In the semiconductor laser device of the present invention, preferably, the two-dimensional diffraction grating and the light emitting layer are formed on one main surface side of the substrate made of GaN. Epitaxial growth of a layer containing a GaN component on a substrate made of GaN yields a GaN crystal with low dislocation density and high flatness, thus lowering the dislocation density of the two-dimensional diffraction grating and the light emitting layer and improving flatness can do. In addition, since the substrate made of GaN has conductivity, it is possible to inject current through the substrate by attaching an electrode to the substrate, and to inject current with high current density into the light emitting layer.

  In the semiconductor laser device of the present invention, the two-dimensional diffraction grating is preferably formed at a position farther from the substrate than the light emitting layer. Thus, the light emitting layer and the two-dimensional diffraction grating are formed in this order on one main surface side of the substrate.

  In the semiconductor laser device of the present invention, the two-dimensional diffraction grating is preferably formed at a position closer to the substrate than the light emitting layer. Thereby, a two-dimensional diffraction grating and a light emitting layer are formed in this order on one main surface side of the substrate.

  In the semiconductor laser device of the present invention, preferably, the low refractive index portion is formed at a position to be a lattice point of a two-dimensional diffraction grating. As a result, light traveling in the high refractive index portion is diffracted in the low refractive index portion and travels again in the high refractive index portion. As a result, a standing wave is generated between each lattice point.

  In the semiconductor laser device of the present invention, the high refractive index portion is preferably formed at a position that is a lattice point of the two-dimensional diffraction grating. As a result, light traveling through the low refractive index portion is diffracted at the high refractive index portion and travels again through the low refractive index portion. As a result, a standing wave is generated between each lattice point.

  In the semiconductor laser device of the present invention, the two-dimensional diffraction grating preferably has a triangular or square lattice shape. The light traveling through these gratings returns to the position of the original grating point through a plurality of diffractions, so that standing waves are likely to occur between the grating points.

  Preferably in the manufacturing method, the step of forming the two-dimensional diffraction grating includes the following steps. A low refractive index portion is formed in one region for forming a two-dimensional diffraction grating. After the step of forming the low refractive index portion, the high refractive index portion is formed in another region for forming the two-dimensional diffraction grating. Thereby, the high refractive index portion can be formed after the low refractive index portion is formed.

  Preferably, in the above manufacturing method, in the step of forming the high refractive index portion, the low refractive index portion is completely covered with the high refractive index portion. Thereby, the layer adjacent to the two-dimensional diffraction grating can be continuously formed of the same material as that of the high refractive index portion.

  Preferably in the manufacturing method, the step of forming the two-dimensional diffraction grating includes the following steps. A high refractive index portion is formed in one region for forming a two-dimensional diffraction grating. After the step of forming the high refractive index portion, the low refractive index portion is formed in another region for forming the two-dimensional diffraction grating. Thereby, the low refractive index portion can be formed after the high refractive index portion is formed.

  Preferably, in the above manufacturing method, in the step of forming the low refractive index portion, the high refractive index portion is completely covered with the low refractive index portion. Thereby, the layer adjacent to the two-dimensional diffraction grating can be continuously formed of the same material as the low refractive index portion.

  Preferably in the manufacturing method, in the step of forming the light emitting layer, the light emitting layer is formed on one main surface side of the substrate. In the step of forming the two-dimensional diffraction grating, the two-dimensional diffraction grating is formed at a position farther from the substrate than the light emitting layer on one main surface side of the substrate. Thus, the light emitting layer and the two-dimensional diffraction grating are formed in this order on one main surface side of the substrate.

  Preferably in the manufacturing method, in the step of forming the light emitting layer, the light emitting layer is formed on one main surface side of the substrate. In the step of forming the two-dimensional diffraction grating, the two-dimensional diffraction grating is formed at a position closer to the substrate than the light emitting layer on one main surface side of the substrate. Thereby, a two-dimensional diffraction grating and a light emitting layer are formed in this order on one main surface side of the substrate.

  According to the semiconductor laser device and the manufacturing method thereof of the present invention, the performance of the semiconductor laser device can be improved. In addition, the reliability of the semiconductor laser element can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
1-3 is a figure which shows the structure of the semiconductor laser element in Embodiment 1 of this invention. 1 is a perspective view, FIG. 2 is a top view, and FIG. 3 is a cross-sectional view taken along line III-III in FIGS. With reference to FIGS. 1-3, the structure of the semiconductor laser element in this Embodiment is demonstrated first.

  The semiconductor laser device 1 includes a substrate 2, an n-type cladding layer 3, a guide layer 4, an active layer 5, a p-type electron block layer 6, a photonic crystal layer 7 as a two-dimensional diffraction grating, and a p-type. A clad layer 8, a p-type contact layer 9, a p-type electrode 10, and an n-type electrode 11 are provided.

  The substrate 2 has two upper surfaces 21 and a lower surface 22 that face each other. On the upper surface 21 side of the substrate 2, an n-type cladding layer 3, a guide layer 4, an active layer 5 as a light emitting layer, and a p-type electron block layer 6 are laminated in this order. These layers are adjacent to each other. A photonic crystal layer 7 is formed on the p-type electron block layer 6. The photonic crystal layer 7 is formed at a position farther from the substrate 2 than the active layer 5. Further, on the photonic crystal layer 7, a p-type cladding layer 8 and a p-type contact layer 9 are laminated in this order. The active layer 5 is sandwiched between the n-type cladding layer 3 and the p-type cladding layer 8. A p-type electrode 10 is formed on the upper surface 21 of the substrate 2, and an n-type electrode 11 is formed on the lower surface 22 of the substrate 2. The p-type electrode 10 has, for example, a circular planar shape, and is in contact with the p-type contact layer 9 at the central portion of the upper surface 91 of the p-type contact layer 9. The n-type electrode 11 is in contact with the lower surface 22 of the substrate 2, for example, the contact extends over the entire surface.

  FIG. 4 is a perspective view schematically showing the configuration of the photonic crystal layer in the first embodiment of the present invention. Referring to FIG. 4, the photonic crystal layer 7 has a high refractive index portion 71 and a low refractive index portion 72. The low refractive index portion 72 has a refractive index lower than that of the high refractive index portion 71. There are a plurality of low refractive index portions 72, which are uniformly distributed inside the high refractive index portion 71. In FIG. 4, the photonic crystal layer 7 constitutes a two-dimensional diffraction grating in the form of a triangular grating. Each of the low refractive index portions 72 is formed at a position that becomes the lattice point 13 of the triangular lattice, in other words, at the position of the apex of the regular triangle. The distances between the center of one lattice point 13 and the centers of six lattice points adjacent to this lattice point are all equal.

Each of the high refractive index portion 71 and the low refractive index portion 72 includes a GaN component. For example, In _y Ga _1-y N (0 ≦ y <1) or Al _x Ga _1-x N (0 ≦ x < 1), Al _x In _y Ga _1-xy N (0 ≦ x <1, 0 ≦ y <1, 0 ≦ x + y ≦ 1). Preferably, the high refractive index portion 71 is made of In _y Ga _1-y N (0 ≦ y ≦ 0.15), and the low refractive index portion 72 is made of Al _x Ga _1-x N (0 ≦ x ≦ 0). .5). Further, the high refractive index portion 71 and the low refractive index portion 72 may be a combination in which the difference between the refractive index of the high refractive index portion 71 and the refractive index of the low refractive index portion 72 is 0.04 or more. preferable. As a combination of the high refractive index portion 71 and the low refractive index portion 72, for example, a combination of GaN and Al _x Ga _1-x N (in this case, 0 <x <1), In _y Ga _1-y N ( In this case, a combination of 0 <y <1) and GaN, or a combination of In _y Ga _1-y N and Al _x Ga _1-x N can be given.

  1 to 3, the n-type cladding layer 3 and the p-type electron block layer 6 function as layers for injecting carriers into the active layer 5. For this reason, the n-type cladding layer 3 and the p-type electron block layer 6 are provided so as to sandwich the active layer 5. The n-type cladding layer 3 and the p-type electron blocking layer 6 both function as confinement layers that confine carriers (electrons and holes) and light in the active layer 5. That is, the n-type cladding layer 3, the active layer 5, and the p-type electron block layer 6 form a double heterojunction. For this reason, carriers contributing to light emission can be concentrated in the active layer 5. Furthermore, the p-type electron block layer 6 also functions as a block layer that blocks the entry of electrons into the photonic crystal layer 7. Thereby, it is possible to suppress non-radiative recombination of electrons and holes in the photonic crystal layer 7.

  The p-type cladding layer 8 functions as a layer for injecting carriers into the active layer 5. The p-type cladding layer 8 functions as a confinement layer for confining carriers (electrons) and light in a layer below the photonic crystal layer 7. The p-type contact layer 9 is formed to make ohmic contact with the p-type electrode 10. The guide layer 4 plays a role of confining carriers and light in the quantum well of the active layer 5.

  The substrate 2 is made of, for example, n-type GaN, SiC, or sapphire, and is particularly preferably GaN. In this case, the upper surface 21 of the substrate 2 is preferably a (0001) plane, for example. The n-type cladding layer 3 is made of, for example, n-type AlGaN, and the guide layer 4 is made of, for example, undoped GaN. The active layer 5 has a multiple quantum well structure made of, for example, InGaN / GaN, the p-type electron block layer 6 and the p-type cladding layer 8 are made of, for example, p-type AlGaN, and the p-type contact layer 9 has For example, it is made of p-type GaN.

Next, the light emission principle of the semiconductor laser element in this embodiment will be described.
When a voltage is applied between the p-type electrode 10 and the n-type electrode 11, holes are injected from the p-type electron blocking layer 6 and the p-type cladding layer 8 into the active layer 5, and the n-type cladding layer 3 to the active layer 5. Electrons are injected into. When holes and electrons are injected into the active layer 5, carrier recombination occurs and light is generated. The wavelength of the generated light is defined by the band gap of the semiconductor layer included in the active layer 5.

  Light generated in the active layer 5 is confined in the active layer 5 by the n-type cladding layer 3, the p-type electron blocking layer 6 and the p-type cladding layer 8, but part of the light is photonic as evanescent light. The crystal layer 7 is reached. When the wavelength of the evanescent light that reaches the photonic crystal layer 7 coincides with the predetermined period of the photonic crystal layer 7, a standing wave is induced at the wavelength corresponding to the period.

  Such a phenomenon can occur in the region immediately below the p-type electrode 10 and in the vicinity thereof because the active layer 5 and the photonic crystal layer 7 are two-dimensionally widened. Laser oscillation can be caused by the feedback effect of standing waves.

  The photonic crystal layer 7 (two-dimensional diffraction grating) has a property of overlapping when translated in the same period in at least two directions. Such a two-dimensional diffraction grating is formed by arranging regular triangles, squares, or regular hexagons all over the surface and providing a lattice point at each vertex. Here, a lattice formed using a regular triangle is referred to as a triangular lattice, a lattice formed using a square is referred to as a square lattice, and a lattice formed using a regular hexagon is referred to as a hexagonal lattice.

  FIG. 5 is a diagram for explaining light diffraction in a triangular lattice. The triangular lattice is filled with regular triangles whose side length is a. In FIG. 5, paying attention to a lattice point A arbitrarily selected from the plurality of lattice points 13, the direction from the lattice point A to the lattice point B is called the X-Γ direction, and from the lattice point A to the lattice point C. The direction to go is called the XJ direction. In the present embodiment, a case will be described in which the wavelength of light generated in the active layer 5 (FIG. 3) corresponds to a lattice period in the X-Γ direction.

The two-dimensional diffraction grating can be considered to include three one-dimensional diffraction grating groups L, M, and N described below. The one-dimensional diffraction grating group L includes one-dimensional gratings L ₁ , L ₂ , L _{3 and the} like provided in the Y-axis direction. The one-dimensional diffraction grating group M is composed of one-dimensional gratings M ₁ , M ₂ , M _{3 and the} like provided with an angle of 120 degrees with respect to the X-axis direction. The one-dimensional diffraction grating group N is composed of one-dimensional gratings N ₁ , N ₂ , N _{3 and the} like provided in a direction of 60 degrees with respect to the X-axis direction. These three one-dimensional diffraction grating groups L, N, and M overlap when rotated at an angle of 120 degrees around an arbitrary grating point. In each one-dimensional diffraction grating group L, N, and M, the interval between the one-dimensional gratings is d, and the interval within the one-dimensional grating is a.

  First, the lattice group L is considered. Light traveling in the direction from the lattice point A to the lattice point B causes a diffraction phenomenon at the lattice point B. The diffraction direction is defined by the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...). Here, λ is the wavelength of light in the high refractive index portion 71 (FIG. 3). When the diffraction grating is formed so as to satisfy the second-order Bragg reflection (m = ± 2), other grating points D, E, F, and θ at angles of θ = ± 60 °, ± 120 °, and G exists. There are also lattice points A and K at angles θ = 0 and 180 ° corresponding to m = 0.

  For example, light diffracted at the lattice point B in the direction of the lattice point D is diffracted according to the lattice group M at the lattice point D. This diffraction can be considered in the same manner as the diffraction phenomenon according to the grating group L. Next, the light diffracted toward the lattice point H at the lattice point D is diffracted according to the lattice group N. In this way, diffraction is sequentially performed at the lattice point H, the lattice point I, and the lattice point J. The light diffracted from the lattice point J toward the lattice point A is diffracted according to the lattice group N.

  As described above, the light traveling from the lattice point A to the lattice point B reaches the first lattice point A through a plurality of diffractions. For this reason, light traveling in a certain direction returns to the position of the original lattice point through a plurality of diffractions, so that a standing wave is generated between the lattice points. Therefore, this two-dimensional diffraction grating acts as an optical resonator, that is, a wavelength selector and a reflector.

  In the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...), The Bragg reflection direction under the condition that m is an odd number is θ = ± 90 °. This means that the diffraction becomes stronger in the direction perpendicular to the main surface of the two-dimensional diffraction grating (the direction perpendicular to the paper surface in FIG. 2). Thereby, light can be emitted (surface emission) in a direction perpendicular to the main surface of the two-dimensional diffraction grating, that is, from the upper surface 91 (FIG. 1) which is a light emission surface.

  Further, in this two-dimensional diffraction grating, considering that the above description is made at an arbitrary grating point A, the above-described light diffraction can occur at all the two-dimensionally arranged grating points. For this reason, it is considered that light propagating in each X-Γ direction is two-dimensionally coupled to each other by Bragg diffraction. In this two-dimensional diffraction grating, it is considered that the three X-Γ directions are coupled by the two-dimensional coupling to form a coherent state.

  FIG. 6 is a perspective view schematically showing another configuration of the photonic crystal layer according to the first embodiment of the present invention. In FIG. 6, the photonic crystal layer 7 constitutes a two-dimensional diffraction grating in the form of a square lattice. Each of the low refractive index portions 72 is formed at a position to be a lattice point 13 of a square lattice, in other words, at a vertex of a square. The distances between the center of one lattice point 13 and the centers of the eight lattice points adjacent to this lattice point are all equal.

  FIG. 7 is a view for explaining light diffraction in a square lattice. The square lattice is filled with squares whose side length is d. In FIG. 7, paying attention to the arbitrarily selected lattice point W, the direction from the lattice point W to the lattice point P is called the X-Γ direction, and the direction from the lattice point W to the lattice point Q is the XJ direction. Call. Here, a case where the wavelength of light generated in the active layer 5 (FIG. 3) corresponds to the lattice period in the X-Γ direction will be described.

The two-dimensional diffraction grating can be considered to include two one-dimensional diffraction grating groups U and V described below. The one-dimensional diffraction grating group U is composed of one-dimensional gratings U ₁ , U ₂ , U _{3 and the} like provided in the Y-axis direction. The one-dimensional diffraction grating group V includes one-dimensional gratings V ₁ , V ₂ , V _{3 and the} like provided in the X-axis direction. These two one-dimensional diffraction grating groups U and V overlap when rotated at an angle of 90 ° about an arbitrary grating point. In each one-dimensional diffraction grating group U and V, the interval between the one-dimensional gratings is d, and the interval within the one-dimensional grating is also d.

  First, the lattice group U will be considered. Light traveling in the direction from the lattice point W to the lattice point P causes a diffraction phenomenon at the lattice point P. The diffraction direction is defined by the Bragg condition 2d · sin θ = mλ (m = 0, ± 1,...) As in the case of the triangular grating. When the diffraction grating is formed so as to satisfy the second-order Bragg reflection (m = ± 2), there are other grating points Q and R at an angle θ = ± 90 °, and m = 0. There are also lattice points W and S at corresponding angles θ = 0 and 180 °.

  The light diffracted toward the lattice point Q at the lattice point P is diffracted according to the lattice group V at the lattice point Q. This diffraction can be considered in the same manner as the diffraction phenomenon according to the grating group U. Next, the light diffracted toward the lattice point T at the lattice point Q is diffracted according to the lattice group U. In this way, the light is sequentially diffracted. The light diffracted from the lattice point T toward the lattice point W is diffracted according to the lattice group V.

  As described above, the light traveling from the lattice point W to the lattice point P reaches the first lattice point W through a plurality of diffractions. For this reason, in the semiconductor laser device of the present embodiment, light traveling in a certain direction returns to the position of the original lattice point through a plurality of diffractions, so that a standing wave is generated between the lattice points. Therefore, this two-dimensional diffraction grating acts as an optical resonator, that is, a wavelength selector and a reflector.

Next, a method for manufacturing the semiconductor laser element in the present embodiment will be described.
First, referring to FIG. 8, a substrate 2 made of, for example, GaN, SiC, or sapphire is prepared. Then, the n-type cladding layer 3, the guide layer 4, the active layer 5, and the p-type electron block layer 6 are formed in this order using, for example, MOCVD (Metal-organic chemical vapor deposition). Is epitaxially grown on the upper surface 21 side. Although not shown, a buffer layer may be formed directly on the substrate 2 and the n-type cladding layer 3 may be formed on the buffer layer. In this case, the crystallinity of each layer can be improved by the buffer layer.

Next, referring to FIG. 9, a layer 72 a made of a low refractive index portion (for example, Al _x Ga _1-x N) is formed on the entire p-type electron block layer 6. Then, a resist 300 having a predetermined pattern is formed on the layer 72a by an electron beam lithography technique. Specifically, a resist for EB (electron beam) exposure is once applied to the entire upper surface of the layer 72a, a desired region of the resist is exposed with EB, and then the resist is developed.

  Next, referring to FIG. 10, layer 72a is etched using resist 300 as a mask. As a result, the low refractive index portion 72 is formed only in the region serving as the lattice point of the two-dimensional diffraction grating, and the layer 72a in the other region is removed. Thereafter, the resist 300 is removed.

  FIG. 11 is a perspective view schematically showing a low refractive index portion in the step shown in FIG. Referring to FIG. 11, each of the plurality of low refractive index portions 72 has a cylindrical shape, and is formed in a region to be a lattice point of a two-dimensional diffraction grating.

  Although the case where the layer 72a is etched using the resist 300 as a mask has been described above, an insulating film such as SiN or a multilayer material may be used as a mask instead of the resist 300.

  Next, after cleaning the surface of the p-type electron block layer 6, the high refractive index portion 71 is formed on the p-type electron block layer 6 by MOCVD. FIGS. 12A to 12F are schematic diagrams sequentially illustrating the growth of the high refractive index portion in the first embodiment of the present invention. 12A to 12F correspond to the A part in FIG.

  Referring to FIGS. 12A to 12F, for example, a high refractive index portion 71 made of GaN is epitaxially grown in a reduced pressure atmosphere. Then, almost no nucleation occurs on the side surface of the low refractive index portion 72, and GaN does not grow from the side surface of the low refractive index portion 72 (abnormal growth in which the growth direction is not the vertical direction). For this reason, GaN (high refractive index portion 71) is selectively epitaxially grown only from the exposed surface of the p-type electron block layer 6 and the upper surface 74 of the low refractive index portion 72 ((a) → (b)). GaN grows upward in the figure. At this time, since the escape of the source gas is large above the low refractive index portion 72, the growth rate of GaN from the surface of the p-type electron block layer 6 is higher than the growth rate of GaN from the upper surface 74 of the low refractive index portion 72. It ’s faster. The effect of this phenomenon is greater when grown under reduced pressure. When the space between the low refractive index portions 72 is completely filled with GaN, the GaN on the upper surface 74 of the low refractive index portion 72 grows in the lateral direction in the figure while continuing to grow in the upward direction in the figure ((b)). → (c)). After continuing the growth in the lateral direction in the figure until the upper surface of GaN becomes almost flat ((c) → (d) → (e)), GaN grows only in the upward direction again ((e) → (f )). Thereby, as shown in FIG. 14, the low refractive index portion 72 is completely covered with the high refractive index portion 71. Note that by suppressing the growth of GaN from the upper surface 74 of the low refractive index portion 72 or by removing GaN above the photonic crystal layer 7, as shown in FIG. GaN does not have to be formed thereon.

  Next, referring to FIG. 3, p-type cladding layer 8 and p-type contact layer 9 are epitaxially grown on photonic crystal layer 7 by using, for example, MOCVD. Thereafter, the p-type electrode 10 is formed on the upper surface 91 of the p-type contact layer 9, and the n-type electrode 11 is formed on the lower surface 22 side of the substrate 2, whereby the semiconductor laser device 1 is completed.

In the conventional case where the GaN-based material is used for the high refractive index portion of the photonic crystal layer and a substance such as SiO _{2 is used} as the low refractive index portion, the inventors of the present application have a high refractive index portion and a low refractive index portion. It was found that a large lattice mismatch occurs between the rate part and the rate part. Further, during and after the formation of the photonic crystal layer, a heat treatment at a high temperature of 1000 ° C. is applied to the photonic crystal layer, so that the thermal expansion coefficient is between the high refractive index portion and the low refractive index portion. It has been found that stress and strain due to the difference occur. Further, it has been found that these lattice mismatches, stresses, and strains deteriorate the characteristics of the active layer for laser emission and, consequently, the characteristics of the semiconductor laser element. In addition, when a substance such as SiO _{2 is used} as the low refractive index portion, an element (for example, silicon) constituting the material such as SiO ₂ diffuses to a nearby layer such as the high refractive index portion or the active layer, It has been found that the reliability of the semiconductor laser element is lowered.

  Therefore, in the semiconductor laser device 1 according to the present embodiment, each of the high refractive index portion 71 and the low refractive index portion 72 constituting the photonic crystal layer 7 is formed of a material containing a GaN component (GaN-based material). Has been. Thereby, since the crystal structure of the high refractive index portion 71 and the crystal structure of the low refractive index portion 72 are close to each other, the lattice mismatch between the high refractive index portion 71 and the low refractive index portion 72 is alleviated. In addition, since the thermal expansion coefficient of the high refractive index portion and the thermal expansion coefficient of the low refractive index portion are close to each other, stress and strain due to the difference in the thermal expansion coefficient are less likely to occur. As a result, the characteristics of the active layer 5 can be improved, and the characteristics of the semiconductor laser device 1 can be improved. In addition, since the low refractive index portion 72 is made of a material containing a GaN component, the high refractive index portion 71 and the active layer 5 are not adversely affected by the diffusion of elements in the low refractive index portion 72. As a result, the reliability of the semiconductor laser element 1 can be improved.

  Here, in general, in the photonic crystal layer, the larger the refractive index difference between the high refractive index portion and the low refractive index portion, the better the characteristics of the photonic crystal layer. In view of this, since the physical properties of the GaN-based material are similar to each other, when each of the high refractive index portion and the low refractive index portion is formed of a GaN-based material as in the present embodiment, There is a concern that the refractive index difference between the refractive index portion and the low refractive index portion becomes small, and the characteristics of the photonic crystal layer deteriorate. However, the inventors of the present application have found that the deterioration of the characteristics of the photonic crystal layer is extremely small even when each of the high refractive index portion and the low refractive index portion is formed of a GaN-based material. In particular, it was found that if the difference in refractive index between the high refractive index portion and the low refractive index portion is 0.04 or more, the light diffraction effect as a photonic crystal can be sufficiently obtained.

  Actually, a photonic crystal layer having a refractive index difference of 0.02 and a photonic crystal layer having a refractive index difference of 0.04 were prepared, and light reflection measurement was performed. As a result, the photonic crystal layer having a refractive index difference of 0.04 has a clear and sharp diffraction peak spectrum corresponding to the lattice constant of the photonic crystal, compared to the photonic crystal layer having a refractive index difference of 0.02. Observed in a direction perpendicular to the photonic crystal plane.

  In particular, in a semiconductor laser element made of a GaN-based material provided with a photonic crystal layer, the emission wavelength is short, and the existence range of evanescent light is limited. Therefore, in order to improve the characteristics of the semiconductor laser element, it is important to bring the active layer and the photonic crystal layer close to each other so that as much evanescent light as possible reaches the photonic crystal layer. For this reason as well, it is important to suppress lattice mismatch, stress, and strain of the photonic crystal layer and to prevent deterioration of the characteristics of the active layer due to these.

Further, since In _y Ga _1-y N (0 ≦ y <1) and Al _x Ga _1-x N (0 ≦ x <1) are similar in physical properties to each other, the high refractive index portion 71 and the low refractive index portion 71 are low. By forming each of the refractive index portions 72 with these materials, lattice mismatch, stress, and strain of the photonic crystal layer 7 can be further suppressed. In particular, the high refractive index portion 71 is formed of In _y Ga _1-y N (0 ≦ y ≦ 0.15), and the low refractive index portion 72 is formed of Al _x Ga _1-x N (0 ≦ x ≦ 0.5). ), The lattice constant of the high refractive index portion 71 and the lattice constant of the low refractive index portion 72 can be made closer to each other while the refractive index difference between the high refractive index portion 71 and the low refractive index portion 72 is maintained. it can.

  Further, by using the substrate 2 made of GaN, the dislocation density of the photonic crystal layer 7 and the active layer 5 can be reduced, and the flatness can be improved. Further, since the substrate made of GaN has conductivity, it is possible to inject current through the substrate by directly attaching the n-type electrode 11 to the substrate 2, and to inject current with high current density into the light emitting layer. Can do.

  Further, since the photonic crystal layer 7 is formed at a position farther from the substrate 2 than the active layer 5, the active layer 5 and the photonic crystal layer 7 are formed on the upper surface 21 side of the substrate 2 in this order. .

  Further, since the low refractive index portion 72 is formed at a position to be a lattice point of the two-dimensional diffraction grating, the light traveling in the high refractive index portion 71 is diffracted by the low refractive index portion 72 and again the high refractive index portion 71. Continue on. As a result, a standing wave is generated between each lattice point.

  The photonic crystal layer 7 has a triangular or square lattice shape. The light traveling through these gratings returns to the position of the original grating point through a plurality of diffractions, so that standing waves are likely to occur between the grating points.

  Further, the high refractive index portion 71 can be formed after the low refractive index portion 72 is formed. Further, when the low refractive index portion 72 is completely covered with the high refractive index portion 71, the layer adjacent to the photonic crystal layer 7 can be continuously formed of the same material as the high refractive index portion 71.

  Note that the configuration and manufacturing method of the semiconductor laser device 1 in the present embodiment are merely an example, and the semiconductor laser device of the present invention includes at least a two-dimensional diffraction grating and a light emitting layer, and is high in the two-dimensional diffraction grating. Each of the refractive index portion and the low refractive index portion only needs to contain a gallium nitride component.

(Embodiment 2)
In the present embodiment, a modified example of the method for manufacturing the semiconductor laser element in the first embodiment will be described.

  First, the n-type cladding layer 3, the guide layer 4, the active layer 5, and the p-type electron block layer 6 are formed on the upper surface 21 of the substrate 2 by using a manufacturing method similar to that of the first embodiment shown in FIG. Form on top.

  Next, referring to FIG. 15, a layer 71 a made of a high refractive index portion (GaN) is formed on the entire p-type electron block layer 6. Then, a resist 310 having a predetermined pattern is formed on the layer 71a by an electron beam lithography technique.

  Next, referring to FIG. 16, layer 71a is etched using resist 310 as a mask. As a result, the layer 71a in the region serving as the lattice point of the two-dimensional diffraction grating is removed, and a hole 76 is formed in this region. Thereby, the high refractive index portion 71 is formed. The Thereafter, the resist 310 is removed.

  Next, after the surface of the p-type electron block layer 6 is cleaned, the low refractive index portion 72 is formed on the p-type electron block layer 6 by MOCVD. FIGS. 17A to 17F are schematic views sequentially illustrating the growth of the low refractive index portion in the second embodiment of the present invention. 17A to 17F correspond to the portion B in FIG.

  Referring to FIGS. 17A to 17F, for example, a low refractive index portion 72 made of GaN is epitaxially grown in a reduced pressure atmosphere. Then, nucleation hardly occurs on the side surface of the high refractive index portion 71, and GaN does not grow from the side surface of the high refractive index portion 71 (abnormal growth in which the growth direction is not the vertical direction). For this reason, GaN (low refractive index portion 72) is selectively epitaxially grown only from the exposed surface of the p-type electron blocking layer 6 and the upper surface 77 of the high refractive index portion 71 ((a) → (b)). GaN grows upward in the figure. At this time, since the source gas is accumulated in the hole 76, the growth rate of GaN from the surface of the p-type electron blocking layer 6 is faster than the growth rate of GaN from the upper surface 77 of the high refractive index portion 71. The effect of this phenomenon is greater when grown under reduced pressure. When the space between the high refractive index portions 71 is completely filled with GaN, the GaN on the upper surface 77 of the high refractive index portion 71 continues to grow in the upward direction in the drawing and also grows in the lateral direction in the drawing ((b ) → (c)). After continuing the growth in the lateral direction in the figure until the upper surface of GaN becomes almost flat ((c) → (d) → (e)), GaN grows only in the upward direction again ((e) → (f )). As a result, the high refractive index portion 71 is completely covered with the low refractive index portion 72. In addition, by suppressing the growth of GaN from the upper surface 77 of the high refractive index portion 71 or by removing GaN above the photonic crystal layer 8, as shown in FIG. GaN does not have to be formed thereon.

  Thereafter, the p-type cladding layer 8, the p-type contact layer 9, the p-type electrode 10, and the n-type electrode 11 are formed using the same manufacturing method as that of the first embodiment, and the semiconductor laser shown in FIG. Element 1 is completed.

  According to the manufacturing method of the semiconductor laser device in the present embodiment, the same effect as that of the manufacturing method of the semiconductor laser device in the first embodiment can be obtained.

  In addition, the low refractive index portion 72 can be formed after the high refractive index portion 71 is formed. Furthermore, when the high refractive index portion 71 is completely covered with the low refractive index portion 72, the layer adjacent to the photonic crystal layer 7 can be continuously formed of the same material as the low refractive index portion 72.

(Embodiment 3)
FIG. 18 is a cross-sectional view showing the configuration of the semiconductor laser element according to Embodiment 3 of the present invention. FIG. 19 is a perspective view showing the configuration of the photonic crystal layer according to Embodiment 3 of the present invention. Referring to FIGS. 18 and 19, in semiconductor laser device 1a of the present embodiment, the structure of photonic crystal layer 7a is different from the structure of the photonic crystal layer of the first embodiment shown in FIG. . That is, in the photonic crystal layer 7 a in the present embodiment, there are a plurality of high refractive index portions 71 and they are uniformly distributed inside the low refractive index portion 72. Each of the high refractive index portions 71 is formed at a position that becomes the lattice point 13 of the triangular lattice, in other words, at the position of the apex of the triangle.

  Since the other configuration of the semiconductor laser element 1a is the same as that of the semiconductor laser element in the first embodiment shown in FIG. 3, the same reference numerals are given to the same members, and the description thereof will not be repeated. .

  According to the semiconductor laser device 1a in the present embodiment, the same effect as that of the semiconductor laser device in the first embodiment can be obtained.

  In addition, since the high refractive index portion 71 is formed at a position to be a lattice point of the two-dimensional diffraction grating, the light traveling through the low refractive index portion 72 is diffracted by the high refractive index portion 71 and is again low. Continue on. As a result, a standing wave is generated between each lattice point.

  In the present embodiment, the case where the high refractive index portion 71 is formed at a position that is a lattice point of a triangular lattice has been described. However, in the present invention, in addition to such a case, the high refractive index portion 71 is also provided. May be formed at a position that becomes a lattice point of a square lattice.

(Embodiment 4)
FIG. 20 is a cross-sectional view showing the configuration of the semiconductor laser element in the fourth embodiment of the present invention. Referring to FIG. 20, in the semiconductor laser element 1b in the present embodiment, the position of the photonic crystal layer 7 (vertical direction in the figure) is the position of the photonic crystal layer in the first embodiment shown in FIG. Is different. That is, the photonic crystal layer 7 in the present embodiment is formed on the n-type cladding layer 3, and the guide layer 4, the active layer 5, and the p-type electron block layer 6 are formed on the photonic crystal layer 7. Formed in order. The photonic crystal layer 7 is formed at a position closer to the substrate 2 than the active layer 5.

  Semiconductor laser device 1b in the present embodiment is manufactured by the following method. First, referring to FIG. 21, n-type cladding layer 3 is epitaxially grown on the upper surface 21 side of substrate 2. Next, the photonic crystal layer 7 is formed on the n-type cladding layer 3 using the same method as in the first embodiment shown in FIGS. The photonic crystal layer 7 is formed at a position closer to the substrate 2 than the active layer 5 on the upper surface 21 side of the substrate 2.

  Next, referring to FIG. 22, the guide layer 4, the active layer 5, and the p-type electron block layer 6 are epitaxially grown on the photonic crystal layer 7 in this order. Thereafter, a p-type cladding layer 8, a p-type contact layer 9, a p-type electrode 10, and an n-type electrode 11 are formed using the same method as in the first embodiment, and the semiconductor laser device 1b shown in FIG. 20 is completed. To do.

  According to the semiconductor laser device 1b and the manufacturing method thereof in the present embodiment, the same effects as those of the semiconductor laser device and the manufacturing method thereof in the first embodiment can be obtained.

  In addition, since the photonic crystal layer 7 is formed at a position closer to the substrate 2 than the active layer 5, the photonic crystal layer 7 and the active layer 5 are formed on the upper surface 21 side of the substrate 2 in this order. .

  In the present embodiment, the case where the low refractive index portion 72 is formed at a position that becomes a lattice point has been described. However, in the present invention, in addition to such a case, the high refractive index portion 71 has a lattice point. It may be formed in the position.

In this example, the semiconductor laser device of the first embodiment shown in FIG. 3 was manufactured and the characteristics thereof were evaluated. Specifically, using a MOCVD method, a buffer layer made of n-type GaN, a clad layer made of n-type AlGaN, and a guide made of undoped GaN are formed on the (0001) plane (front surface) of the n-type GaN substrate. A layer, an active layer having a multiple quantum well structure made of InGaN / GaN, an electron block layer made of p-type AlGaN, and a layer made of p-type Al _0.05 Ga _0.95 N were epitaxially grown. Then, after removing the substrate from the furnace in which the epitaxial growth was performed, an EB exposure resist (ZEP520, manufactured by Nippon Zeon Co., Ltd.) was applied to the entire upper surface of the layer made of p-type Al _0.05 Ga _0.95 N. Further, after exposing a desired region of the resist with an electron beam to draw a pattern, the resist was developed. Subsequently, a layer made of p-type Al _0.05 Ga _0.95 N was etched using this resist as a mask. This etching was performed by using ICP (Inductively Coupled Plasma) of Cl-based gas or HI-based gas under vertical etching conditions mainly in the milling process. Thereafter, the resist was removed using benzenesulfonic acid. As a result, a low refractive index portion made of p-type Al _0.05 Ga _0.95 N was formed at a position to be a lattice point of the two-dimensional diffraction grating. FIG. 23 is a photomicrograph of the low refractive index portion produced in Example 1 of the present invention. Referring to FIG. 23, it can be seen that a plurality of low refractive index portions having a cylindrical shape are formed reflecting the pattern of the resist. As described above, since the dry etching process mainly including the physical reaction process (milling) is easy to control, the in-plane uniformity of the lattice point shape of the two-dimensional diffraction grating can be improved. Next, a high refractive index material made of p-type GaN was epitaxially grown on the p-type electron block layer by using a low pressure MOCVD method, and the low refractive index material was embedded with the high refractive index material. Thereby, a photonic crystal layer was formed on the p-type electron block layer. For this photonic crystal layer, a square lattice with a pitch between adjacent lattice points of 160 nm was used, the filling rate was 15%, and the thickness (the height of the column of the low refractive index portion) was 100 nm. Next, a cladding layer made of p-type AlGaN and a contact layer made of p-type GaN were formed on the photonic crystal layer. Then, a p-type electrode was formed on the p-type contact layer, and an n-type electrode was formed on the back surface of the substrate. The surface morphology after epitaxial growth of the high refractive index part was good.

Subsequently, the characteristics of the obtained semiconductor laser device were evaluated. The coupling coefficient κ (kappa) between the photonic crystal layer and the active layer emission estimated based on the split width of the diffraction peak was about 120 cm ⁻¹ . Further, pulse oscillation was observed at a threshold of 8 kA / cm ² at room temperature. As a result, the semiconductor laser device obtained in this example has a longer device life and reliability than the conventional semiconductor laser device in which the low refractive index portion made of SiO ₂ is embedded with the high refractive index portion made of GaN. It turned out to be a highly functional device.

In this example, the semiconductor laser device of the fourth embodiment shown in FIG. 20 was manufactured and its characteristics were evaluated. Specifically, a buffer layer made of n-type GaN and a clad layer made of n-type AlGaN were epitaxially grown on the (0001) plane (front surface) of the n-type GaN substrate using MOCVD. Subsequently, a photonic crystal layer having a low refractive index layer made of n-type GaN and a high refractive index layer made of n-type In _0.04 Ga _0.96 N was formed by the same method as in Example 1. For this photonic crystal layer, a triangular lattice having a pitch between adjacent lattice points of 190 nm was used, the filling rate was 15%, and the thickness (the height of the column of the low refractive index portion) was 100 nm. Next, on the photonic crystal layer, a guide layer made of undoped GaN, an active layer having a multiple quantum well structure made of InGaN / GaN, an electron block layer made of p-type AlGaN, and a clad layer made of p-type AlGaN And a contact layer made of p-type GaN. Then, a p-type electrode was formed on the p-type contact layer, and an n-type electrode was formed on the back surface of the substrate. The surface morphology after epitaxial growth of the high refractive index part was good.

Subsequently, the characteristics of the obtained semiconductor laser device were evaluated. The coupling coefficient κ (kappa) between the photonic crystal layer and the active layer emission estimated based on the split width of the diffraction peak was about 150 cm ⁻¹ . Further, pulse oscillation was observed at a threshold of 7 kA / cm ² at room temperature. As a result, the semiconductor laser device obtained in this example has a longer device life and reliability than the conventional semiconductor laser device in which the low refractive index portion made of SiO ₂ is embedded with the high refractive index portion made of GaN. It turned out to be a highly functional device.

  The embodiments and examples disclosed above are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  The present invention can be used for a semiconductor laser device having a two-dimensional diffraction grating and a manufacturing method thereof.

It is a perspective view which shows the structure of the semiconductor laser element in Embodiment 1 of this invention. It is a top view which shows the structure of the semiconductor laser element in Embodiment 1 of this invention. FIG. 3 is a cross-sectional view taken along line III-III in FIGS. 1 and 2. It is a perspective view which shows typically the structure of the photonic crystal layer in Embodiment 1 of this invention. It is a figure for demonstrating the diffraction of the light in a triangular lattice. It is a perspective view which shows typically the other structure of the photonic crystal layer in Embodiment 1 of this invention. It is a figure for demonstrating the diffraction of the light in a square lattice. It is sectional drawing which shows the 1st process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. It is sectional drawing which shows the 3rd process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. It is a perspective view which shows typically the low-refractive-index part in the 3rd process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. It is a schematic diagram which shows the mode of the growth of the high refractive index part in the 4th process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. (A) is the first state, (b) is the second state, (c) is the third state, (d) is the fourth state, (e) is the fifth state, and (f) is the sixth state. Yes. It is sectional drawing which shows the 5th process of the manufacturing method of the semiconductor laser element in Embodiment 1 of this invention. In Embodiment 1 of this invention, it is a perspective view which shows typically the photonic crystal layer of the state in which the low refractive index part was completely covered by the high refractive index part. It is sectional drawing which shows the 1st process of the manufacturing method of the semiconductor laser element in Embodiment 2 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the semiconductor laser element in Embodiment 2 of this invention. It is a schematic diagram which shows the mode of the growth of the low refractive index part in the 3rd process of the manufacturing method of the semiconductor laser element in Embodiment 2 of this invention. (A) is the first state, (b) is the second state, (c) is the third state, (d) is the fourth state, (e) is the fifth state, and (f) is the sixth state. Yes. It is sectional drawing which shows the structure of the semiconductor laser element in Embodiment 3 of this invention. It is a perspective view which shows typically the structure of the photonic crystal layer in Embodiment 3 of this invention. It is sectional drawing which shows the structure of the semiconductor laser element in Embodiment 4 of this invention. It is sectional drawing which shows the 1st process of the manufacturing method of the semiconductor laser element in Embodiment 4 of this invention. It is sectional drawing which shows the 2nd process of the manufacturing method of the semiconductor laser element in Embodiment 4 of this invention. It is a microscope picture of the low refractive index part produced in Example 1 of this invention.

Explanation of symbols

  1, 1a, 1b Semiconductor laser device, 2 substrate, 3 n-type cladding layer, 4 guide layer, 5 active layer, 6 p-type electron block layer, 7, 7a photonic crystal layer, 8 p-type cladding layer, 9 p-type Contact layer, 10 p-type electrode, 11 n-type electrode, 13 lattice points, 21 substrate upper surface, 22 substrate lower surface, 71 high refractive index portion, 71a high refractive index portion layer, 72 low refractive index portion, 72a low refractive index portion Layer, 74 upper surface of low refractive index portion, 76 holes, 77 upper surface of high refractive index portion, 91 upper surface of p-type contact layer, 300, 310 resist.

Claims (17)

A two-dimensional diffraction grating having a high refractive index portion and a low refractive index portion having a refractive index lower than that of the high refractive index portion;
A light emitting layer that is formed on one main surface side of the two-dimensional diffraction grating and emits light by injecting carriers;
Each of the high refractive index portion and the low refractive index portion includes a gallium nitride component.   2. The semiconductor laser device according to claim 1, wherein a difference between a refractive index of the high refractive index portion and a refractive index of the low refractive index portion is 0.04 or more. The high refractive index portion and the low refractive index portion are each composed of In _y Ga _1-y N (0 ≦ y <1) or Al _x Ga _1-x N (0 ≦ x <1). 2. The semiconductor laser device according to 2. The high refractive index portion is made of In _y Ga _1-y N (0 ≦ y ≦ 0.15), and the low refractive index portion is made of Al _x Ga _1-x N (0 ≦ x ≦ 0.5). The semiconductor laser device according to claim 3.   The semiconductor laser device according to claim 1, wherein the two-dimensional diffraction grating and the light emitting layer are formed on one main surface side of a substrate made of gallium nitride.   The semiconductor laser device according to claim 5, wherein the two-dimensional diffraction grating is formed at a position farther from the substrate than the light emitting layer.   The semiconductor laser device according to claim 5, wherein the two-dimensional diffraction grating is formed at a position closer to the substrate than the light emitting layer.   The semiconductor laser device according to claim 1, wherein the low refractive index portion is formed at a position to be a lattice point of the two-dimensional diffraction grating.   The semiconductor laser device according to claim 1, wherein the high refractive index portion is formed at a position to be a lattice point of the two-dimensional diffraction grating.   The semiconductor laser element according to claim 1, wherein the two-dimensional diffraction grating has a triangular or square lattice shape. Forming a two-dimensional diffraction grating having a high refractive index portion and a low refractive index portion having a refractive index lower than the refractive index of the high refractive index portion;
Forming a light emitting layer that emits light by injecting carriers on one main surface side of the two-dimensional diffraction grating,
The method for manufacturing a semiconductor laser device, wherein each of the high refractive index portion and the low refractive index portion includes a gallium nitride component.   The step of forming the two-dimensional diffraction grating includes the step of forming the low refractive index portion in one region for forming the two-dimensional diffraction grating and the step of forming the low refractive index portion. The method for manufacturing a semiconductor laser device according to claim 11, further comprising: forming the high refractive index portion in another region for forming a two-dimensional diffraction grating.   13. The method of manufacturing a semiconductor laser device according to claim 12, wherein in the step of forming the high refractive index portion, the low refractive index portion is completely covered with the high refractive index portion.   The step of forming the two-dimensional diffraction grating includes the step of forming the high refractive index portion in one region for forming the two dimensional diffraction grating and the step of forming the high refractive index portion. The method of manufacturing a semiconductor laser device according to claim 11, further comprising: forming the low refractive index portion in another region for forming a two-dimensional diffraction grating.   The method of manufacturing a semiconductor laser device according to claim 14, wherein in the step of forming the low refractive index portion, the low refractive index portion completely covers the high refractive index portion.   In the step of forming the light emitting layer, in the step of forming the light emitting layer on one main surface side of the substrate and forming the two-dimensional diffraction grating, the light emitting layer on the one main surface side of the substrate The method of manufacturing a semiconductor laser device according to claim 11, wherein the two-dimensional diffraction grating is formed at a position away from the substrate.   In the step of forming the light emitting layer, in the step of forming the light emitting layer on one main surface side of the substrate and forming the two-dimensional diffraction grating, the light emitting layer on the one main surface side of the substrate The method for manufacturing a semiconductor laser device according to claim 11, wherein the two-dimensional diffraction grating is formed at a position close to the substrate.