JP5344676B2 - LIGHT EMITTING BOARD AND LIGHT EMITTING ELEMENT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the flatness of a light emitting end surface, and to turn an emission wavelength into a long wavelength to a green region, in a light emitting element using a non-polar substrate or a semi-polar substrate. <P>SOLUTION: In a non-polar AlInGaN substrate used as the substrate of the light emitting element, when an AlInGaN mixed crystal composition is expressed as Al<SB>(x)</SB>In<SB>(y)</SB>Ga<SB>(1-x-y)</SB>N, 0&le;x&le;1, 0&le;y&le;1, a point (x, y) is set in a region of a quadrangle with a point A(0.68, 0.32), a point B(0.19, 0.17), a point C(0.16, 0.55) and a point D(0.38, 0.62) as vertexes. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a substrate used for a light-emitting element such as an optical amplifier, a light-emitting diode, or a semiconductor laser, and a light-emitting element using the substrate.

  Since the realization of high-intensity blue light-emitting diodes (LEDs), nitride semiconductors have received much attention as materials for light-emitting devices in the ultraviolet to visible light region. To date, blue, green, and white light-emitting diodes have been put into practical use, and are used, for example, for traffic signals, various indicators, illumination, liquid crystal backlights, and the like. Furthermore, the development of semiconductor lasers using this material has progressed, and blue-violet and pure blue lasers have been developed so far, which have been put to practical use in next-generation DVD (Blu-ray) light sources and full-color displays, respectively. It is being done. However, as the technology advances in this way, a green semiconductor laser, which is one of the three primary colors of light, has not yet been realized, and this is the origin of the term “Green Gap Problem”.

  In order to realize a green semiconductor laser, the simplest approach is to increase the In composition (x) of In (x) Ga (1-x) N used in the light emitting layer of the blue semiconductor laser. It is. However, when the In composition of the InGaN light-emitting layer is increased, an electric field inside the light-emitting layer called a piezo electric field is generated, which significantly reduces the light-emitting efficiency in the light-emitting layer and is a factor that hinders the realization of a green laser. It has become. As a method for solving this “electric field” problem, it has been proposed to fabricate an element on a substrate having a crystal plane orientation different from the conventional one. Specifically, instead of the conventionally used GaN (0001) plane (C plane) substrate, a category substrate plane orientation called a nonpolar plane or semipolar plane is used to suppress the piezoelectric field. Proposals have been made. Here, the nonpolar plane is a plane perpendicular to the C plane, and the semipolar plane is a plane inclined by 40 to 65 degrees from the C plane.

If these plane orientations are used, it is theoretically predicted that the piezo electric field is greatly reduced. Recently, even in a blue laser actually formed on a nonpolar plane (m-plane), a result suggesting that the piezoelectric field is greatly suppressed has been obtained (see Non-Patent Document 1).
Applied Physics Express 1 (2008) 011102

  Even if the configuration of the semiconductor laser described in Non-Patent Document 1 is used, a green laser is not realized. One of the causes is the flatness of the laser resonator mirror end face. When a laser element is fabricated on a nonpolar plane GaN substrate, it is necessary to form a resonator stripe parallel to the c-axis in order to obtain a large optical gain of the laser. This means that the end face of the resonator mirror is a C-plane, but the C-plane is not a charge-neutral plane, so it cannot be cleaved easily, and even if it can be cleaved, it is ideally flat. This is because it is difficult to form a mirror surface.

  In the lasers on nonpolar planes reported so far, the resonator mirror is usually the C plane, but this laser cannot be extended to the green region because the flatness of the C plane resonator mirror is ensured. It is thought that the cause is not possible. The above discussion applies to laser elements on a semipolar substrate in a similar manner, and it is difficult to form a flat resonator mirror surface.

  The present invention has been made in view of these problems, and the object thereof is to improve the flatness of the light emitting end face in a light emitting device using a nonpolar substrate or a semipolar substrate, and to extend the emission wavelength to the green region. Is to provide technology.

One embodiment of the present invention is a light-emitting element substrate. When the mixed crystal composition is expressed as Al _(x) In _(y) Ga _(1-xy) N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, the light emitting element substrate has a point (x, y). Vertices A point (0.68, 0.32), B point (0.19, 0.17), C point (0.16, 0.55) and D point (0.38, 0.62) And a nonpolar AlInGaN mixed crystal substrate located in a rectangular region.

  According to this aspect, when the light emitting element is formed, the light emitting end face can be a charge neutral surface. The charge neutral surface can be easily cleaved, and the flatness can be improved as compared with the C surface. As a result, the light emission wavelength of the light emitting element can be extended to the green region. Further, since distortion in the light emitting layer is suppressed, the crystal can be grown in a state in which the crystal structure of the light emitting layer is well maintained.

  In the light emitting element substrate of the above aspect, the points (x, y) are A ′ point (0.3, 0.2), B point (0.19, 0.17), C point (0.16, 0. 55) and D ′ point (0.3, 0.59) may be located in a rectangular area having the vertex.

Another embodiment of the present invention is a light emitting element substrate. When the mixed crystal composition is expressed as Al _(x) In _(y) Ga _(1-xy) N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, the light emitting element substrate has a point (x, y). Are E point (0.69, 0.31), F point (0.16, 0.15), G point (0, 0.27), H point (0, 0.5) and I point (0. And a semipolar AlInGaN mixed crystal substrate located in a pentagonal region having a vertex of 39, 0.61).

  In the light emitting element substrate of the above aspect, the points (x, y) are E ′ point (0.3, 0.19), F point (0.16, 0.15), G point (0, 0.27). , H point (0, 0.5) and I ′ point (0.3, 0.58) may be located in a pentagonal region.

  Yet another embodiment of the present invention is a light emitting element. The light-emitting element includes a light-emitting element substrate according to any one of the aspects described above and a quantum well structure formed on the light-emitting element substrate and provided between the n-type cladding layer and the p-type cladding layer. A light emitting layer.

  In the light-emitting element of the above aspect, the optical gain of polarized light emitted from the light-emitting layer is stronger in the direction in which the c-axis is projected onto the substrate surface than in the direction perpendicular to the c-axis in the substrate surface. May be parallel to the direction in which the c-axis is projected onto the substrate surface.

Yet another embodiment of the present invention is a light emitting element. In the light-emitting element, the main surface is a nonpolar plane or a semipolar plane, and the mixed crystal composition is Al _(x) In _(y) Ga _(1-xy) N, 0 ≦ x <1, 0 <y <. 1. An AlInGaN mixed crystal substrate expressed as x + y <1, and a light emitting layer formed on the AlInGaN mixed crystal substrate and having a quantum well structure provided between the n-type cladding layer and the p-type cladding layer The strain of the light emitting layer is -2% to + 2%, and the light emitting end face of the light emitting layer is a charge neutral surface.

  According to this aspect, the flatness can be improved as compared with the C plane by setting the light emitting end face of the light emitting element to be a charge neutral plane. As a result, the light emission wavelength of the light emitting element can be extended to the green region. In addition, when the crystal growth of the light emitting layer is suppressed, the crystal structure of the light emitting layer can be maintained well.

  In the light-emitting element of the above-described aspect, the optical gain of the polarized light emitted from the light-emitting layer is a point (from the range in which the direction in which the c-axis is projected onto the substrate surface is stronger than the direction perpendicular to the c-axis in the substrate surface ( x, y) may be selected. The emission wavelength of light emitted from the light emitting layer may be 500 to 550 nm.

  ADVANTAGE OF THE INVENTION According to this invention, in the light emitting element using a nonpolar board | substrate or a semipolar board | substrate, the flatness of a light emission end surface can be improved and the light emission wavelength can be lengthened to a green region.

  Hereinafter, embodiments and examples of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

(Embodiment)
The substrate for a light emitting device according to the embodiment is an AlInGaN mixed crystal substrate in which the main surface of the substrate is a nonpolar plane or a semipolar plane. The nonpolar plane is a plane perpendicular to the C plane, and examples thereof include an m plane and an a plane. The semipolar plane is a plane having an angle of 40 to 65 degrees with the C plane, and examples thereof include (11-22) plane and (10-12) plane. Examples of the electric field neutral plane include a nonpolar plane (m plane, a plane) and a semipolar plane. The AlInGaN mixed crystal substrate is suitably used as a substrate for a compound semiconductor light emitting device such as a light emitting diode having at least one Pn junction, a semiconductor laser, or a semiconductor optical amplifier.

The AlInGaN mixed crystal substrate has a mixed crystal composition represented by Al _(x) In _(y) Ga _(1-xy) N, 0 ≦ x <1, 0 <y <1, and x + y <1. That is, In and Ga are essential, and Al is an arbitrary component.

  The following items may be mentioned as conditions for the composition of AlInGaN.

Condition (1) “The optical gain of X2 polarized light is the maximum among X1 polarized light, X2 polarized light and X3 polarized light with respect to the polarized light emitted from the light emitting layer”
X1 polarized light, X2 polarized light, and X3 polarized light are defined as follows. That is, as shown in FIG. 1, X1 polarized light is polarized light perpendicular to the c-axis in the substrate plane. X2 polarized light is polarized light in a direction in which the c-axis is projected onto the substrate surface. X3 polarized light is polarized light in a direction perpendicular to the substrate. The “polarization direction” refers to the “direction of the electric field vector of light”.

Condition (2) “The strain of the light emitting layer is in the range of −2% to + 2%”
By adjusting the composition of AlInGaN so as to meet the condition (1), X2 polarized light can be used instead of the X1 polarized light used in the conventional light emitting device. For this reason, the light emitting end face of the light emitting element can be changed from a conventional C plane to a charge neutral plane. More specifically, when the main surface of the AlInGaN mixed crystal substrate is a nonpolar plane (m plane), the light emitting end face can be a nonpolar plane (a plane). Further, when the main surface of the AlInGaN mixed crystal substrate is a nonpolar plane (a plane), the light emitting end face can be a nonpolar plane (m plane). In this case, the c-axis shown in FIG. 1 is perpendicular to the X3 direction, and the angle θ formed by the c-axis and the X3 axis is 90 degrees. When the main surface of the AlInGaN mixed crystal substrate is a semipolar plane, the light emitting end face can be a charge neutral plane such as a nonpolar plane (m plane) or a nonpolar plane (a plane). In this case, the angle θ formed by the c-axis and the X3 axis shown in FIG. 1 is 40 to 65 degrees. Specifically, when the main surface of the AlInGaN mixed crystal substrate is a (11-22) plane (θ = 58 degrees), the light emitting end face can be a nonpolar plane (m plane). In addition, when the main surface of the AlInGaN mixed crystal substrate is a (10-12) plane (θ = 43 degrees), the light emitting end face can be a nonpolar plane (a plane).

  Further, by adjusting the composition of AlInGaN so as to meet the condition (2), the distortion of the light emitting layer is suppressed, and the crystal structure of the light emitting layer can be favorably maintained when crystal growth is performed.

  Thereby, for example, when a semiconductor laser is formed using the substrate for a light emitting element according to the embodiment, the end face of the resonator mirror can be a charge neutral surface. Since the charge neutral surface does not need to separate the positive charge and the negative charge that are attracted to each other by Coulomb force, it can be easily cleaved, and the flatness can be improved as compared with the C surface. As a result, the emission wavelength of the semiconductor laser can be extended to the green region (500 to 550 nm).

Example 1
FIG. 2 is a schematic diagram illustrating the structure of the semiconductor laser diode 10 according to the first embodiment. The semiconductor laser diode 10 includes a substrate 20, an n-type semiconductor layer 30 formed in order on the substrate 20 by crystal growth, a light emitting layer 40, a p-type semiconductor layer 50, and an n-side electrode 60 provided on the back surface of the substrate 20. And a p-side electrode 70 formed on the p-type semiconductor layer 50.

  The substrate 20 of Example 1 is a nonpolar AlInGaN mixed crystal substrate having a nonpolar plane (m-plane) as a main surface. The nonpolar AlInGaN mixed crystal substrate can be formed using, for example, the MOCVD method. The thickness of the substrate 20 is, for example, 100 μm. The composition of AlInGaN will be described later.

  The n-type semiconductor layer 30 includes an n-GaN layer 32, an n-AlGaN cladding layer 34, and an n-InGaN guide layer 36 in this order from the substrate 20 side.

  The n-GaN layer 32 is a low resistance layer for making ohmic contact with the n-side electrode 60. The n-GaN layer 32 is formed, for example, by doping Si with GaN as an n-type impurity.

  The n-AlGaN cladding layer 34 has a refractive index smaller than that of the n-InGaN guide layer 36 and has a heterojunction with the n-InGaN guide layer 36. Thereby, the n-AlGaN cladding layer 34 has a role of confining the light emitted from the light emitting layer 40 in the light emitting layer 40. Specifically, the n-AlGaN cladding layer 34 is formed by doping, for example, Si as an n-type impurity in AlGaN. The thickness of the n-AlGaN cladding layer 34 is, for example, 1 μm.

  The n-InGaN guide layer 36 has a role of confining light from the light emitting layer 40. Specifically, the n-InGaN guide layer 36 is formed by doping InGaN with, for example, Si as an n-type impurity. The thickness of the n-InGaN guide layer 36 is, for example, 0.1 μm. The n-InGaN guide layer 36 only needs to be able to confine light from the light emitting layer 40 and does not need to contain an n-type impurity.

  On the other hand, the p-type semiconductor layer 50 is provided on the light emitting layer 40, and in order from the p-side electrode 70 side, the p-GaN layer 52, the p-AlGaN cladding layer 54, the p-InGaN guide layer 56, and the p-AlGaN. A block layer 58 is included.

  The p-GaN layer 52 is a low resistance layer for making ohmic contact with the p-side electrode 70. The p-GaN layer 52 is formed by doping, for example, Mg as a p-type impurity in GaN.

  The p-AlGaN cladding layer 54 has a refractive index smaller than that of the p-InGaN guide layer 56 and has a heterojunction with the p-InGaN guide layer 56. Thereby, the p-AlGaN cladding layer 54 has a role of confining the light emitted from the light emitting layer 40 in the light emitting layer 40. Specifically, the p-AlGaN cladding layer 54 is formed by doping, for example, Mg as a p-type impurity in AlGaN. The thickness of the p-AlGaN cladding layer 54 is, for example, 0.5 μm.

  The p-InGaN guide layer 56 has a role of confining light from the light emitting layer 40. Specifically, the p-InGaN guide layer 56 is formed by doping, for example, Mg as a p-type impurity in InGaN. The thickness of the p-InGaN guide layer 56 is, for example, 0.1 μm. The p-InGaN guide layer 56 only needs to be able to confine light from the light emitting layer 40 and does not need to contain a p-type impurity.

  The p-AlGaN block layer 58 has a role of suppressing the outflow of electrons from the light emitting layer 40 and increasing the efficiency of recombination of electrons and holes. Specifically, the p-AlGaN block layer 58 is formed by doping, for example, Mg as a p-type impurity in AlGaN.

The light emitting layer 40 has a multiple quantum well structure (MQW) in which three layers of InGaN layers (quantum well layers) and GaN layers (barrier layers) doped with Si are alternately stacked, and electrons, holes, Recombines to emit light and amplify the emitted light. The composition of the InGaN layer used in the light emitting layer 40 of this example is In _0.3 Ga _0.7 N. The thicknesses of the InGaN layer and the GaN layer are 3 nm and 5 nm, respectively. The light emitted from the light emitting layer 40 is green, and the emission wavelength is, for example, 530 nm.

  The n-side electrode 60 is electrically connected to the back surface of the substrate 20. The n-side electrode 60 is made of Al, for example.

  The p-side electrode 70 is provided on the p-type semiconductor layer 50 in a stripe shape in a direction perpendicular to the c-axis. The p-side electrode 70 is made of, for example, Pd / Au.

  In the semiconductor laser diode 10 having the layer structure described above, since the quantum well surface of the light emitting layer 40 is a nonpolar surface (m-plane), the piezoelectric field is greatly reduced. Further, the end face of the resonator mirror is a nonpolar plane (a-plane) that is a charge neutral plane. For this reason, cleavage at the end face of the resonator mirror can be easily performed, and the flatness of the end face of the resonator mirror can be improved.

(Calculation of polarization characteristics)
Regarding the semiconductor laser diode 10 described above, the relationship between the polarization characteristics and the AlInGaN composition in the nonpolar AlInGaN mixed crystal substrate was examined according to the following calculation method, and a composition region satisfying the above condition (1) was calculated.

  In general, the polarization characteristics of a compound semiconductor light emitting device are mainly determined by the electronic state of the valence band of the quantum well. For this reason, in calculating the polarization characteristics of the semiconductor laser diode 10, the electronic state of the valence band of the strained quantum well of the light emitting layer 40 was modeled as follows.

  In bulk InGaN, there are three bands called A, B, and C near the top of the valence band, and the electronic states of these gamma points are almost | X + iY>, | X-iY>, | Z>. Yes. As shown in FIG. 3, in the optical transition from the conduction band to the valence band, the transition to A and B is allowed only for the polarization in the C plane, and the transition to C is for the polarization in the c-axis direction. Only allowed.

  In an InGaN strained quantum well, the above-described three valence band bands are mixed due to strain and quantum well effects, so that the polarization characteristics are completely different from those of the bulk. For this reason, by using 6 × 6 k · p Hamiltonian (see SLChuang and CSChang: Phys. Rev. B54, 2491 (1996)), the above effect is taken into account and the InGaN strain on the nonpolar AlInGaN mixed crystal substrate. The electronic state of the valence band of the quantum well was calculated. In the calculation, an infinite barrier quantum well was assumed and the electric field in the quantum well was zero. For the electronic state of the valence band, only the gamma point was calculated. The optical matrix elements were calculated for the three different polarizations (X1, X2, X3) shown in FIG. 1 for the band edge emission between the ground states of the conduction band and the valence band.

When such a calculation represents the composition of the substrate 20 as Al _(x) In _(y) Ga _(1-xy) N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, (x, y) is expressed as Each was carried out by changing independently in the range of 0 ≦ x ≦ 1 and 0 ≦ y ≦ 1. At each point (x, y), the optical gains of X1 polarized light, X2 polarized light, and X3 polarized light were calculated, and the maximum polarized light among these three polarized lights was specified.

  FIG. 4 is a diagram showing the maximum polarized light among the polarized lights from the light emitting layer in the phase diagram of the nonpolar AlInGaN composition. Regions R1, R2, and R3 shown in FIG. 4 indicate regions where the optical gains of the X1-polarized light, the X2-polarized light, and the X3-polarized light are maximized, respectively. The region R2 is a region that satisfies the above-described condition (1). By setting the AlInGaN composition in the region R2, the nonpolar surface (a surface) can be used as the resonator mirror end surface (light emitting end surface). The point (x, y) that satisfies the condition (1) and the condition that the distortion of the light emitting layer in the condition (2) is in the range from −2% to + 2% is the point A (0.68, 0. 32), located within a quadrangular area having points B (0.19, 0.17), C (0.16, 0.55) and D (0.38, 0.62) as vertices Was found.

  In the AlInGaN composition, the proportion of AlN is desirably 30% or less. Since the atomic radius of In atoms (1.63 Å) and the atomic radius of Al atoms (1.43 Å) are greatly different, if the proportion of AlN is higher than 30%, it becomes difficult to mix InN and AlN. It becomes difficult to grow an AlInGaN mixed crystal substrate. On the other hand, when the AlN ratio is higher than 30%, the electrical resistance increases, and the emission intensity of the semiconductor laser diode 10 is reduced.

  For this reason, it is desirable to consider that “the ratio of AlN is 30% or less” as the condition (3) to the above-described conditions (1) and (2). When the condition (3) is taken into consideration, the point (x, y) is the point A ′ (0.3, 0.2), point B (0.19, 0.17), point C (0.16). , 0.55) and D ′ point (0.3, 0.59) were found to lie within a rectangular area.

(Example 2)
FIG. 5 is a schematic diagram illustrating the structure of the semiconductor laser diode 10 according to the second embodiment. In the semiconductor laser diode 10 according to the second embodiment, a semipolar AlInGaN mixed crystal substrate having a semipolar plane as a main surface is used as the substrate 20, and the surfaces of the n-type semiconductor layer 30, the light emitting layer 40, and the p-type semiconductor layer 50 are used. Are different from the first embodiment in that they are semipolar planes (θ shown in FIG. 1 is 58 degrees). Since the other configuration of the semiconductor laser diode 10 according to the second embodiment is the same as that of the first embodiment, the description thereof is omitted as appropriate.

  In the semiconductor laser diode 10 according to the second embodiment, since the quantum well surface of the light emitting layer 40 is a semipolar surface, the piezoelectric field is greatly reduced. Further, the end face of the resonator mirror is a nonpolar plane (m plane) or a nonpolar plane (a plane) which is a charge neutral plane. For this reason, cleavage at the end face of the resonator mirror can be easily performed, and the flatness of the end face of the resonator mirror can be improved.

  Regarding the semiconductor laser diode 10 according to Example 2, the polarization characteristics of the light emitting layer 40 were analyzed in the same manner as in Example 1.

  FIG. 6 is a diagram showing the maximum polarized light among the polarized lights from the light emitting layer in the phase diagram of the semipolar AlInGaN composition. Regions R1, R2, and R3 shown in FIG. 6 indicate regions where the optical gains of the X1-polarized light, the X2-polarized light, and the X3-polarized light are maximized, respectively. The region R2 is a region that satisfies the above-described condition (1). By setting the AlInGaN composition in the region R2, the nonpolar plane (m-plane) can be the resonator mirror end face (light emitting end face). The point (x, y) that satisfies the condition (1) and that the strain of the light emitting layer in the condition (2) is in the range from −2% to + 2% is the point E (0.69, 0). .31), F point (0.16, 0.15), G point (0, 0.27), H point (0, 0.5) and I point (0.39, 0.61) as vertices It was found to be located within a pentagonal region.

  Further, when the above condition (3) is taken into consideration, the point (x, y) is the point E ′ (0.3, 0.19), the point F (0.16, 0.15), the point G. It was found to be located in a pentagonal region having (0, 0.27), point H (0, 0.5) and point I ′ (0.3, 0.58) as vertices.

It is a schematic diagram showing how to take the coordinate axis in the (light emitting layer) quantum well on an arbitrary plane orientation substrate. 1 is a schematic diagram showing the structure of a semiconductor laser diode according to Example 1. FIG. It is a schematic diagram which shows the selection rule of the optical transition in InGaN. It is a figure which shows the largest polarized light among each polarized light from a light emitting layer in the phase diagram of a nonpolar AlInGaN composition. FIG. 6 is a schematic diagram showing the structure of a semiconductor laser diode according to Example 2. In the phase diagram of a semipolar AlInGaN composition, it is a figure which shows the largest polarized light among each polarized light from a light emitting layer.

Explanation of symbols

  10 semiconductor laser diode, 20 substrate, 30 n-type semiconductor layer, 40 light emitting layer, 50 p-type semiconductor layer, 60 n-side electrode, 70 p-side electrode

Claims (8)

A substrate for a light emitting device in which an InGaN layer having an emission wavelength of 500 to 550 nm is formed as a quantum well layer provided between an n-type cladding layer and a p-type cladding layer,
When the mixed crystal composition is expressed as Al (x) In (y) Ga (1-xy) N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
Points (x, y) are point A (0.68, 0.32), point B (0.19, 0.17), point C (0.16, 0.55) and point D (0.38, A substrate for a light-emitting element, comprising a nonpolar AlInGaN mixed crystal substrate located in a rectangular region having an apex at 0.62).   Point (x, y) is A ′ point (0.3, 0.2), B point (0.19, 0.17), C point (0.16, 0.55) and D ′ point (0. The substrate for a light-emitting element according to claim 1, further comprising a nonpolar AlInGaN mixed crystal substrate located in a rectangular region having a vertex at 3,0.59). A substrate for a light emitting device in which an InGaN layer having an emission wavelength of 500 to 550 nm is formed as a quantum well layer provided between an n-type cladding layer and a p-type cladding layer,
When the mixed crystal composition is expressed as Al (x) In (y) Ga (1-xy) N, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1,
Point (x, y) is E point (0.69, 0.31), F point (0.16, 0.15), G point (0, 0.27), H point (0, 0.5) And a semipolar AlInGaN mixed crystal substrate located in a pentagonal region having an I point (0.39, 0.61) as a vertex.   Point (x, y) is E 'point (0.3, 0.19), F point (0.16, 0.15), G point (0, 0.27), H point (0, 0.5). And a semipolar AlInGaN mixed crystal substrate located in a pentagonal region having the vertices at I) and I ′ points (0.3, 0.58). 5. The substrate for a light emitting device according to claim 1, wherein an In _0.3 Ga _0.7 N layer is formed as the quantum well layer. A substrate for a light emitting device according to any one of claims 1 to 5,
A light emitting layer formed on the light emitting element substrate and having a quantum well structure provided between an n-type cladding layer and a p-type cladding layer;
A light-emitting element comprising: The optical gain of polarized light emitted from the light emitting layer is stronger in the direction in which the c axis is projected onto the substrate surface than in the direction perpendicular to the c axis in the substrate surface,
The light emitting element according to claim 6 , wherein a light emitting end face from which light emitted from the light emitting layer is emitted is parallel to a direction in which the c-axis is projected onto the substrate surface. The main surface is a nonpolar plane or a semipolar plane, and the mixed crystal composition is Al (x) In (y) Ga (1-xy) N, 0 ≦ x <1, 0 <y <1, x + y <1 AlInGaN mixed crystal substrate represented by
A light emitting layer formed on the AlInGaN mixed crystal substrate and including an InGaN layer as a quantum well layer provided between the n-type cladding layer and the p-type cladding layer ;
With
The strain of the light emitting layer is -2% to + 2%,
The light emitting end surface of the light emitting layer is a charge neutral surface;
The point (x, y) is selected from the range in which the optical gain of the polarized light emitted from the light emitting layer is stronger in the direction in which the c-axis is projected onto the substrate surface than in the direction perpendicular to the c-axis in the substrate surface. ,
The light emitting element characterized by the emission wavelength of the light emitted from the said light emitting layer being 500-550 nm .

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