JPH10135576A - Semiconductor light-emitting element, optical semiconductor element, light-emitting diode, and display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a threshold current density required for optical oscillation by forming an active layer with a specific property on a second semiconductor layer that is formed via a first semiconductor layer on a substrate main surface, forming a third semiconductor layer with a different property on it, and making the direction of the film thickness of the active layer different from the axis of one-axis anisotropy. SOLUTION: A second semiconductor layer 13 is formed on the main surface of a substrate 11 directly or via a first semiconductor layer 12, and an active layer 14 whose energy band gap is smaller than the second semiconductor layer 13 and is made of a semiconductor with one-axis anisotropy is formed on the second semiconductor layer 13. Further, a third semiconductor layer 15 with a larger energy band gap than that of the active layer 14 is formed on the active layer 14. Then, a pair of electrodes 17 and 18 for causing current to flow in the direction of a film thickness are provided on the second semiconductor layer 13, the active layer 14, and the third semiconductor layer 15, where at least the direction of the film thickness of the active layer 14 is different from the axis of the one-axis anisotropy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, an optical semiconductor device, a light emitting diode, and a display device, and more particularly to a wurtzite type such as GaN that emits light in a wavelength band from blue to ultraviolet. The present invention relates to a semiconductor light emitting device, an optical semiconductor device, a light emitting diode, and a display device having a compound semiconductor in a light emitting section.

[0002]

2. Description of the Related Art In recent years, as a light source for an optical disk, a short wavelength laser having a wavelength in a range from blue to ultraviolet has been actively developed. As a blue laser light source, there are an optical element using a II-VI group ZnSe-based material and an optical element using a III-V group GaN-based material. Among them, there is a report that ZnSe-based materials lead the research on semiconductor lasers, and that room-temperature continuous oscillation can be already obtained. However, since ZnSe-based materials are inherently easily deteriorated, there is a problem in reliability, and they have not yet been put to practical use.

[0003] On the other hand, several years ago, high-brightness L using GaN was used.
Since the announcement of the ED, Ga has excellent environmental resistance
N has been reviewed and sees a huge increase in researchers worldwide. Then, in 1996, Nichia introduced a semiconductor laser that oscillates using InGaN. Since the GaN-based semiconductor used as the light-emitting element is a wurtzite compound semiconductor, MOVP is formed on a hexagonal sapphire substrate or 6H-SiC substrate having a similar crystal structure.
Epitaxial growth was performed using the E method (metal organic chemical vapor deposition). Here, “H” of 6H—SiC is
Indicates that the crystal has 6th-order rotational symmetry.
“6” indicates that the crystal is a crystal having a six-phase synchronous structure in which an arrangement of atoms or molecules of six phases is periodically formed.

[0004] Hexagonal sapphire substrate or 6H-Si
A semiconductor laser using a C substrate is formed by the following procedure. When using a sapphire substrate,
For example, as shown in FIG. 24A, an n-type Al _0.1 Ga _0.9 N cladding layer 143 and an n-type Al _0.1 Ga _0.9 N clad layer 143 are provided on a sapphire (0001) substrate 141 having a (0001) plane as a main surface via a GaN buffer layer 142. GaN light guide layer 144, Ga _0.9 ln _0.1 N active layer 145, p-type GaN light guide layer 146, and p-type Al
The _0.1 Ga _{0 .9} N cladding layer 147 after epitaxially grown by MOVPE method, n-type Al etching
_0.1 Ga _0.9 N part of the cladding layer 143 to expose the, provided with an n-side electrode made of Ti / Au electrode 148 on the exposed surface, p-type Al _0.1 Ga _{0. 9} N Ni is formed on the cladding layer 147 /
A p-side electrode made of an Au electrode 149 is provided, and a semiconductor laser is formed by such a process.

On the other hand, in the case of using a 6H-SiC substrate, as shown in FIG. 24 (b), (0001) Si plane or,
An n-type Al _0.1 Ga layer is formed on the Si surface of the 6H—SiC (0001) substrate 151 via an n-type AIN buffer layer 152.
_0.9 N clad layer 153, n-type GaN optical guide layer 154, Ga
_0.9 ln _0.1 N active layer 155, p-type GaN optical guide layer 156,
And MOVPE of the p-type Al _0.1 Ga _0.9 N clad layer 157
After epitaxial growth by the method, 6H
-Ti / Au electrode 15 on the back of SiC (0001) substrate 151
8 and an n-side electrode made of p-type Al _0.1 Ga _0.9 N
A semiconductor laser is formed through a step of providing a p-side electrode made of a Ni / Au electrode 159 on the cladding layer 157.

In such a conventional light emitting device, GaN is used.
-Based epitaxial layers 142 to 147, 152 to 157
Is a sapphire (0001) substrate 141 or 6H-S
In the <0001> direction of the iC (0001) substrate 151, (0
Since the (001) plane grew, the in-plane strain became isotropic, and the Ga _0.9 ln _0.1 N active layers 145 and 155 remained uniaxially anisotropic. The <0001> direction is the c-axis direction.

Next, the energy band structure of a GaN-based semiconductor will be described. FIG. 25A is a diagram showing the band structure of the valence band of the GaN-based semiconductor in a state where no distortion is applied. The bands of HH (Heavy Hole) and LH (Light Hole) are almost degenerate. In a GaN-based semiconductor, the CH band is close. In the conventional light emitting device shown in FIG. 24A, the in-plane lattice constant of the n-type Al _0.1 Ga _0.9 N clad layer 143 to the p-type Al _0.1 Ga _0.9 N clad layer 147 is just above the GaN buffer layer 142. N-type Al _0.1 Ga
_Since it is specified by the lattice constant of the _0.9 N cladding layer 143,
The coherently grown n-type GaN light guide layer 144 to p-type GaN light guide layer 146 receive compressive stress due to lattice mismatch and difference in thermal expansion coefficient.

[0008] The same applies to the device shown in FIG. 24 (b), but subjected to tensile stress by thermal expansion coefficient difference, Ga _0.9 l
With respect to the n _0.1 N active layer 155, the influence of strain due to the lattice constant is strong, and a compressive stress acts. In addition to the above semiconductor lasers, the present inventors have found that the optical gain of GaN is much higher than that of conventional materials, and confirmed that this material is suitable for a surface emitting laser.

Next, a surface emitting laser will be described. An optical resonator (vertical resonator) having a resonance axis in a direction perpendicular to the active layer formed on the substrate is provided, and has a structure to emit light in a direction perpendicular to the surface of the active layer. Such a surface emitting semiconductor laser has a short cavity length and a low threshold current, can easily realize a two-dimensional array of semiconductor laser devices, has a large number of devices per unit wafer area, or has a device as a wafer. The surface emitting laser which oscillates short-wavelength light for optical discs or short-distance optical communication has been developed especially for optical disks or for short-distance optical communication.

However, in the surface emitting laser of the conventional material, since the direction of the polarization plane of the oscillating light is not fixed, the polarization plane changes during use, or a kink may occur in the emission output characteristic due to the change in the polarization plane. . In this case, reading of an optical disk using polarized light cannot be performed, writing and reading with light cannot be performed stably, and more stable communication cannot be realized.

Therefore, it is necessary to fix and stabilize the polarization plane direction of the oscillation light of the surface emitting semiconductor laser.
The active layer of a conventional surface emitting semiconductor laser has been deposited on a substrate having a (001) plane of a zinc blende type crystal as a main surface.
On the other hand, when a surface-emitting semiconductor laser having a hexagonal semiconductor represented by GaN as an active layer is configured in a similar structure, a substrate having a (0001) plane perpendicular to the c-axis of the hexagonal crystal as a main surface is formed on a substrate. It is expected that an active layer will be deposited. Hereinafter, a conventional surface emitting semiconductor laser having such a structure will be described.

FIG. 26 is a perspective view of a conventional surface emitting semiconductor laser, showing the basic structure of a surface emitting semiconductor laser having a vertical cavity. As shown in FIG.
Is made of a hexagonal crystal, for example, sapphire, and has a c-axis 104
It has a main surface perpendicular to. Alternatively, the substrate 1 has the (001) plane of the zinc blende type crystal as the main surface. On the substrate 101, a barrier layer 107 of the first conductivity type, an active layer 102, and a barrier layer 108 of the second conductivity type are sequentially and sequentially deposited.
Further, the reflecting mirror 103 made of a disc-shaped multilayer film is formed on the barrier layer 108 of the second conductivity type. This reflecting mirror 103
Is a reflection surface, and the lower surface of the barrier layer 107, that is, the interface between the barrier layer 107 and the substrate 101 is another reflection surface, and has a reflection surface parallel to the active layer 102 and a resonance axis perpendicular to the active layer 102. An optical resonator is configured.

In a surface emitting semiconductor laser using an active layer of zinc blende type crystal which is currently realized, the reflecting mirror 103 has a semiconductor multilayer structure and is provided on both reflecting surfaces of the optical resonator. On the other hand, the surface emitting semiconductor laser using GaN having a large optical gain as the active layer is the above-described reflector 103
It is said that oscillation can be achieved by providing one of them. Also,
The oscillating light is emitted from an optical window formed on the lower surface of the substrate 101 (opposite the main surface).

The active layer 10 of the above-described surface emitting semiconductor laser
2 is epitaxially deposited on the substrate 101. Therefore, the active layer 102 made of a hexagonal crystal or a zinc blende crystal
Is formed as a thin layer in which the hexagonal c-axis or the <001> axis of the zinc blende type crystal is perpendicular to the plane. On the other hand, since the resonator has a resonance axis perpendicular to the active layer 102, the oscillated light travels perpendicular to the active layer 102, and the surface of the active layer 102 becomes a polarization defining surface. That is, the polarization defining plane is defined as the xy plane, and the traveling direction of light is defined as z.
When taking the axis, the oscillating light is an x-polarized light 1 whose polarization plane includes the x-axis.
05 and y-polarized light 106 whose polarization plane includes the y-axis. The z-axis is perpendicular to the active layer 2, that is, parallel to the hexagonal c-axis or the <001> axis of the zinc blende crystal, and forms a rotationally symmetric axis of optical anisotropy. The y-polarized light 106 has the same optical coupling with the crystal. Therefore, crystallographically, both the x-polarized light 105 and the y-polarized light 106 can oscillate with the same intensity, so that the plane of polarization of the oscillated light is not determined and the plane of polarization becomes unstable.

In order to stabilize the plane of polarization of such oscillation light,
By making the reflector elliptical or rectangular, the x-polarized light 105
Alternatively, a semiconductor laser that oscillates only one of the y-polarized light 106 has been developed. However, this semiconductor laser has a problem that the emitted light does not become a circular beam, and it is difficult to precisely manufacture the shape of the reflecting mirror. Further, in order to eliminate such inconvenience, the active layer 102 or the barrier layers 107, 1
A semiconductor laser has been proposed in which the in-plane refractive index distribution is formed at 08 to degrade the symmetry of the refractive index around the z-axis and define the polarization plane of oscillation light. However, a process for forming the refractive index distribution is required, and it is inevitable that the manufacturing process becomes complicated.

[0016]

In the case of a conventional GaN-based semiconductor, the energetically highest bands HH and LH in the valence band are double degenerate.
Since holes are distributed in both the HH and LH bands in an N-based semiconductor, there has been a problem that the threshold current density for causing laser oscillation is high.

Further, when a GaN-based semiconductor is grown on a 6H-SiC substrate, cracking is likely to occur on the (0001) plane of the GaN-based semiconductor layer due to stress caused by thermal expansion, and the GaN-based semiconductor has good crystallinity. It is difficult to obtain. When the Ga _0.9 ln _0.1 N active layers 145 and 155 constituting the light emitting portion are subjected to a compressive stress due to a difference in thermal expansion coefficient and lattice mismatch in the (0001) plane, as shown in FIG. In addition, the energy of the CH band further changes from the unstrained state to HH,
Only a band structure relatively lower than LH is obtained, and the energetically highest bands HH and LH in the valence band remain doubly degenerated.

Further, another cause of the high threshold current density is that the sapphire substrate has no cleavage. In addition to these problems, in the conventional surface emitting semiconductor laser having a vertical cavity, the polarization plane of oscillation light is not fixed because the in-plane anisotropy of the active layer is small, and the polarization plane of the emitted light can be fixed. Cannot be performed or oscillation is not stable.

In a structure in which the reflecting mirror is rectangular and the plane of polarization is defined, there is a problem that the emitted light becomes a circular beam, and it is difficult to form a rectangular pattern as the size of the light is reduced. Further, the method of forming an in-plane refractive index in the active layer or the barrier layer has a limitation in simplification of a manufacturing process. The fact that the plane of polarization of the oscillating light is not determined poses another problem when a surface emitting semiconductor laser is used as a light source for a magneto-optical disk drive.

That is, in the magneto-optical disk device, it is necessary that the polarization planes of the laser beams are aligned in order to read the data by detecting the rotation of the polarization plane of the light. However, conventional surface emitting lasers are not used as data reading elements because their polarization planes are not uniform. The present invention can reduce the threshold current density required for light oscillation, have a GaN-based semiconductor layer in which cracking is unlikely to occur, and can fix the polarization plane of light and suppress the fluctuation of the polarization plane in a surface emitting semiconductor laser. It is an object to provide a semiconductor light emitting device, an optical semiconductor device, a light emitting diode, and a display device.

[0021]

The above-mentioned object is achieved by forming the semiconductor device directly or via the first semiconductor layer 12 (52) on the main surface of the substrate 11 (41) as illustrated in FIG. 2 or FIG. A second semiconductor layer 13 (47) formed on the second semiconductor layer 13 (47) and having an energy band gap smaller than that of the second semiconductor layer 13 (47). The active layer 14 (4
2), a third semiconductor layer 15 (48) formed on the active layer 14 (42) and having an energy band gap larger than that of the active layer 14 (42), and a second semiconductor layer 13 (47). ), The active layer 14 (42) and the third
And a pair of electrodes 17, 18 (10a, 10b) for flowing a current in the thickness direction of the semiconductor layer 15 (48). At least the thickness direction of the active layer 14 (42) is the uniaxial anisotropic direction. The problem is solved by a semiconductor light emitting device characterized in that the direction is different from the sex axis.

In the above semiconductor light emitting device, as shown in FIG. 2, the semiconductor constituting the active layer 14 (42) is a wurtzite nitride semiconductor. The wurtzite nitride is Al _x Ga _1-xy In _y N, the composition ratio x is 0 ≦ x ≦ 1, and the composition ratio y is 0 ≦ y ≦ 1
In the xy coordinates, the composition ratio x and the composition ratio y are represented by a straight line indicating y = 0.214x−0.328 and y =
It is characterized by being present in the range between the straight lines indicating 0.353x-0.209.

In the semiconductor light emitting device, the substrate 1
1 (41) is made of any one of GaN, AlN, and SiC,
The main surface is a {11-20} plane or {1-100}
Or {1-20} or {1-100} inclined from −5 ° to + 5 ° from the {1-100} plane. In the semiconductor light emitting device, the substrate 11
(41) is a LiAlO ₂ substrate, wherein the main surface is a {100} surface or a surface turned off at an angle of −5 ° to + 5 ° from the {100} surface.

In the above-mentioned semiconductor light emitting device, the active layer 14 (42) has a uniaxial anisotropic crystal structure, and is subjected to a strain in a plane not perpendicular to the c-axis indicating anisotropy. It is characterized by having in-plane strain anisotropy.
Further, the active layer 14 _{(42), AI x Ga 1-xy ln} y N
(Where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1).

In the semiconductor light emitting device, the second semiconductor layer 13 is formed of Al _u Ga _1-uv ln _v N (where 0 ≦ u ≦ 1).
, 0 ≦ v ≦ 1) consists, and the third semiconductor layer 15 is _{Al w Ga 1-wz 1n z} N ( where, 0 ≦ w ≦ 1,0 ≦ z
≦ 1). In the semiconductor light emitting device, the lattice constant a of the a-axis of the active layer 14 (42)
₁ and the lattice constants a ₂ and a ₃ of the a-axis of the second semiconductor layer and the third semiconductor layer satisfy the relationship of a ₁ <a ₂ and a ₁ <a ₃ . Further, the active layer 14
The c-axis lattice constant c _{1 of} (42) and the c-axis lattice constants c ₂ and c _{3 of} the second semiconductor layer and the third semiconductor layer are represented by:
It is characterized by satisfying the relations of c ₁ <c ₂ and c ₁ <c ₃ .

In the semiconductor light emitting device, the lattice constant a ₁ of the a-axis of the active layer 14 (42) and the lattice constants of the a-axis of the second semiconductor layer and the third semiconductor layer, a ₂ , a ₃
Satisfy the relationships of a ₁ > a ₂ and a ₁ > a ₃ . The c-axis lattice constant c _{1 of the} active layer 14 (42) and the c-axis lattice constants c ₂ and c _{3 of} the second semiconductor layer and the third semiconductor layer are c ₁ > c _2. , C ₁ > c
It is characterized by satisfying the relationship of ₃ .

In the semiconductor light emitting device, the substrate 1
1 is a {1-100} plane or {11-2}.
Off angle θ to any of the 0 ° planes (where 0 ° ≦ θ ≦
The substrate is turned off by 10 °). Alternatively, the substrate 11, the 213 and the third semiconductor layers 15, and the active layer 14 may have a {0001} plane, a {1-1} plane.
Wherein the main surface of the substrate 41 is a small surface having a plane orientation that intersects the {0001} plane. 8. The semiconductor light emitting device according to claim 7, wherein said active layer formed above said small surface is a light emitting portion.
The facet is formed in a plane orientation perpendicular to either the {1-100} plane, the {11-20} plane or the {0001} plane, and the {1-100} plane or the {11-20} plane Alternatively, the {0001} plane is a cleavage plane at both ends of the resonator.

In the semiconductor light emitting device described above, FIG.
As shown in FIG. 2, a mirror layer is formed below the second semiconductor layer 42 or above the third semiconductor layer 48, and the active layer 42, the second and third layers are formed with the mirror layer as one end. A resonator is formed in the thickness direction of the semiconductor layers 47 and 48. In this case, the resonance wavelength of the resonator is a wavelength at which the photoluminescence light intensity is maximized. Further, the active layer 42 is made of Ga.
First layer of N or lnGaN and AlGalnN or GaN or InGaN
Characterized by comprising a multi-quantum well layer having a multilayer structure of the second layer, a GaN single layer, an lnGaN single layer or an AlGalnN single layer. Further, the main surface of the substrate 41 is
It is either the (11-20) plane or the (1-100) plane of the SiC substrate or the (1-102) plane of the sapphire substrate.

The above-mentioned problem is caused by the first conductivity type AIGaN grown on the SiC substrate 41 having the (11-20) plane as the main surface.
A first barrier layer 47 comprising a GaN layer or an lnGaN layer, a multiple quantum well layer including a GaN layer or an lnGaN layer, an active layer 42 comprising a GaN layer or an lnGaN layer deposited on the first barrier layer 47; A second barrier layer 48 of AIGaN of the second conductivity type deposited on the second barrier layer 42 and a reflecting mirror 43 of a multilayer film provided on the second barrier layer 48 are used as a first reflecting surface. The semiconductor light emitting device is characterized by having a thickness direction optical resonator having a second reflection surface below the first barrier layer 47 and first and second electrodes 50a and 50b.

Further, as shown in FIG. 18, the above-described problem is caused by forming a substrate 53 having a (11-20) plane as a main surface and a c-axis parallel to the main surface, and forming the substrate 53 above the substrate 53. A first active layer 58 made of a wurtzite structure crystal, a first barrier layer 56 containing a first conductivity type impurity formed under the first active layer 58, and a first active layer A second barrier layer 60 containing impurities of the second conductivity type formed on top of the first active layer 58 and the first and second barrier layers 56 and 60 for flowing a current in the film thickness direction. A surface emitting semiconductor laser 66 having electrodes 64 and 65, and a second active layer electrically separated from the surface emitting semiconductor laser 66 and formed above the substrate 53 and made of wurtzite structure crystal 5
8, a first semiconductor layer 56 including a first conductivity type impurity formed below the second active layer 58, and a second active layer 5
6, a current flowing in the thickness direction of the second semiconductor layer 58 containing the second conductivity type impurity and the second active layer 58 and the first and second semiconductor layers 56, 58 And a light receiving element 67 having electrodes 64 and 65 for taking out the light.

In this case, the first active layer 56 of the semiconductor laser 66 and the second active layer 56 of the light receiving element 67 are made of GaN, InGaN, AlGaN or AlGaInN. The optical semiconductor device according to the above. Also,
The first and second barrier layers 5 of the semiconductor laser 66
6, 58 and the first and second semiconductor layers 56, 58 of the light receiving element 67 are made of GaN, InGaN, AlGaN or AlGaInN.
It is characterized by consisting of.

Further, the substrate 53 is made of one of silicon carbide and sapphire. Further, the substrate 53 has a hexagonal structure, and the main surface is a {1-100} plane or a {11-20} plane. The above-mentioned object is achieved by a light-emitting diode 70 characterized in that the c-axis direction of a wurtzite compound semiconductor crystal is substantially orthogonal to the light emission direction, as illustrated in FIG.

Further, the c-axis direction of the wurtzite compound semiconductor crystal is substantially orthogonal to the crystal growth direction. The wurtzite compound semiconductor crystal is a group III-V compound semiconductor made of a group III nitride. Further, as illustrated in FIG. 23, a plurality of light emitting diodes 98 made of a wurtzite compound semiconductor crystal whose light emission direction is substantially orthogonal to the c-axis direction,
And a light emitting diode for the right eye polarized in one direction and a light emitting diode for the left eye polarized in a direction perpendicular to the polarization direction of the light emitting diode among the plurality of light emitting diodes. A display device characterized in that the display device is arranged so as to obtain a three-dimensional display.

Next, the operation of the above-described invention will be described. In the present invention, by selecting the main surface of the substrate, the c-type of the hexagonal or wurtzite type semiconductor layer formed on the substrate is determined.
The axis is not perpendicular to the plane of the semiconductor layer. Therefore, when compressive or tensile strain in the plane direction is applied to the hexagonal or wurtzite active layer formed on the substrate, the active layer has triaxial anisotropy. As a result, the degeneracy of the active layer in the valence band is released, and the oscillation threshold current of the semiconductor laser having such an active layer is reduced.

According to such a structure, the plane of polarization (optical anisotropy) of light emission by the compound semiconductor layer can be uniquely determined. In addition, when a surface emitting semiconductor laser is formed by growing such an active layer on a substrate, the in-plane anisotropy of the active layer is increased and the electric field vector is determined in one direction, so that the polarization can be determined. .

As described above, when the plane of polarization of the oscillation light of the surface emitting semiconductor laser is uniquely determined, it can be used as a light source for a magneto-optical disk drive, and the light receiving element can be mounted on the same substrate as the surface emitting semiconductor laser. It is easy to manufacture. As a result, the work of mounting the semiconductor laser and the light receiving element, which has been conventionally performed, becomes unnecessary, and the size of the light receiving / emitting device is further reduced.

As the substrate, a wurtzite structure such as GaN, a tetragonal crystal such as LiAlO ₂ , sapphire, 6H—
A hexagonal crystal such as SiC is used. Further, as a main surface of the substrate, a (1-100) plane or (11-20)
Use face. By the way, when the c-axis direction of the wurtzite compound semiconductor crystal constituting the light emitting diode is set to be substantially orthogonal to the light emission direction, the polarization direction is determined. Therefore, a plurality of such light-emitting diodes are arranged on the display surface of the display device, and one or more light-emitting diodes constitute a part or all of the pixels, and the polarization directions of adjacent light-emitting diodes are different from each other by 90 degrees. Let it. Thereby, the light emitting diode for the right eye polarization direction and the light emitting diode for the left eye polarization can be adjacent to each other, and the number of parts can be reduced by omitting the deflector in the stereoscopic display device, and the manufacturing cost can be reduced. Moreover, such a display device has a bright image.

[0038]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention. (First Embodiment) FIGS. 1A and 1B are configuration diagrams of a first embodiment of the present invention. In the semiconductor laser shown in FIGS. 1A and 1B, a first semiconductor layer 1 having a uniaxial anisotropic crystal structure is used as a light emitting portion, and is perpendicular to an axis indicating the anisotropy of the first semiconductor layer 1. In other words, a three-dimensional anisotropy is provided by applying a strain in a plane other than the above.

Thus, the axis indicating anisotropy (ie, c
When strain is applied in a plane that is not perpendicular to (axis), the applied strain isotropically shows triaxial anisotropy in each direction. As a result, HH and L in the valence band
The degeneracy of H is released, and the threshold current density for laser oscillation is reduced. That is, as shown in FIG. 1 (b), the degeneracy of the bands of HH and LH, which were at the top in terms of energy, is released and LH
, HH and a band of a crystalline field split hole (CH), an energy difference is generated between the bands. Therefore, for laser oscillation, carriers need only be transferred to HH, and the threshold current density increases. At this time, a resonator is manufactured perpendicular to the direction of the electric field vector determined by the polarization of the top band.

On the other hand, as described in the prior art, in a semiconductor laser having an active layer in which a compressive stress is applied in the (0001) plane of a GaInN layer perpendicular to the c-axis, HH is required to cause laser oscillation. , LH must be filled with carriers, and the threshold current density increases. In FIG. 1A, the first semiconductor layer 1 is sandwiched between second and third semiconductors 2 and 3 having a different lattice constant from that of the first semiconductor layer 1, and the interface between the layers is the second semiconductor. It is not perpendicular to the axis indicating the anisotropy of one semiconductor layer 1.

As described above, the main surface of the light emitting portion composed of the first semiconductor layer 1 is constituted by a surface which is not perpendicular to the c-axis, and the second semiconductor 2 and the second semiconductor 2 having a different lattice constant from the first semiconductor layer 1 are formed. When the first semiconductor layer 1 is sandwiched between the third semiconductor layers 3, a strain is applied in a plane that is not perpendicular to the c-axis based on the difference in their lattice constants, so that the light emitting portion has triaxial anisotropy. Can be. Next, materials for the first to third semiconductor layers 1, 2, and 3;
The crystal lattice constant will be described.

As a material constituting the first semiconductor layer 1, for example, AI _x Ga _1-xy In _y N (where 0 ≦ x ≦
1, 0 ≦ y ≦ 1) is used. Such a wurtzite-type nitride semiconductor is most typical and useful as a semiconductor material for a light-emitting element having uniaxial anisotropy. Al _u Ga _1-uv In _v N is used as a material for forming the second semiconductor layer 2.
(Where 0 ≦ u ≦ 1, 0 ≦ v ≦ 1), and Al _w Ga _1-wz In _{z is} used as a material forming the third semiconductor layer 3.
N (where 0 ≦ w ≦ 1, 0 ≦ z ≦ 1) is adopted. As the second semiconductor layer 2 and the third semiconductor layer 3, GaN having a different mixed crystal ratio from the first semiconductor layer 1 made of the same GaN-based material is used.
By using a system semiconductor, stress can be applied to the first semiconductor layer 1 without deteriorating the crystallinity. The mixed crystal ratio of the second semiconductor layer 2 and the third semiconductor layer 3 may be the same.

Further, the lattice constant a ₁ of the a-axis of the first semiconductor layer 1 and the a-axis of the second semiconductor layer 2 and the third semiconductor layer 3
The lattice constants a ₂ and a _{3 of the} axes are a ₁ <a ₂ and a ₁ <a ₃
To satisfy the relationship. In addition, the first semiconductor layer 1
Between the lattice constant c ₁ of c-axis, a second lattice constant c ₂ of the c-axis of the semiconductor layer 2 and the third semiconductor layer 3, c ₃ is, c ₁ <c
₂ , so as to satisfy the relationship of c ₁ <c ₃ .

With such a lattice constant relationship, an in-plane biaxial tensile stress can be applied to the first semiconductor layer 1, whereby the band degeneracy can be resolved and the threshold current density can be reduced. . In this case, the energy difference between the highest band of the valence band and the second band is larger than the compressive stress (see FIG. 14).
In addition, since the top band is at LH, the threshold current density is further reduced.

[0045] By contrast, the lattice constant a ₁ of the first a-axis of the semiconductor layer 1, and the second a-axis lattice constant a ₂ of the semiconductor layer 2 and the third semiconductor layer 3, a ₃ is, a ₁ > a ₂ , a ₁ >
to satisfy the relation of a _3. The c-axis lattice constant c _{1 of} the first semiconductor layer 1 and the c-axis lattice constants c ₂ and c _{3 of} the second semiconductor layer 2 and the third semiconductor layer 3 are c ₁ >
The relationship of c ₂ , c ₁ > c ₃ is satisfied.

With such a relation of the lattice constant, a compressive stress (strain) can be applied in the plane of the first semiconductor layer 1, whereby the degeneracy of the HH and LH bands is solved, and the threshold current density is reduced. In addition to the above, there is no need to worry about the occurrence of cracks as compared with the case where tensile stress occurs, so that the reliability is further improved. Also, the second semiconductor layer 2
And the energy band gap of the third semiconductor layer 3 is
A material and a film thickness that are larger than the energy gap of the first semiconductor layer 1 are selected. By setting such a relation of the energy band gap, light and carriers are confined in the first semiconductor layer 1, and efficient light emission can be obtained.

Further, as a constituent material of the substrate constituting the semiconductor laser, a material formed of GaN, AIN, or SiC is selected. When a substrate composed of GaN, AIN, or SiC having a uniaxial anisotropic crystal structure was used as a semiconductor substrate constituting a semiconductor laser, the substrate was grown on the substrate by appropriately selecting its main surface. When strain is applied to the first semiconductor layer 1, the first semiconductor layer 1 can have triaxial anisotropy.

The first semiconductor layer provided on the substrate constituting the semiconductor laser has the same composition as the substrate. For example, using a GaN-based mixed crystal substrate, a cladding layer having the same composition is provided directly on the base slope. Thereby, strain can be effectively applied to the first semiconductor layer 1 constituting the light emitting section on the cladding layer. Next, the plane orientation of the substrate will be described.

The main surface of the semiconductor substrate constituting the semiconductor laser was turned off from either the {1-100} plane or the {11-20} plane by an off angle θ (0 ° ≦ θ ≦ 10 °). Form on the surface. In the present specification, an index usually represented by "1 bar" or "2 bar" is represented by "-1" or "-2" for convenience. When a semiconductor having a uniaxial anisotropic crystal structure is used as a substrate constituting a semiconductor laser, the principal surface of the semiconductor laser is set to a {1-100} plane or a {11-20} plane, whereby a first semiconductor above the substrate is formed. The layer 1 can be given a triaxial anisotropy by applying a strain. In this case, as shown in FIG. 1 (c), the off-angle θ (where 0 ° ≦ θ ≦ 10
°) Only the main surface may be turned off.

Also, the cleavage planes constituting the resonator of the semiconductor laser are {0001} plane, {1-100) plane, and
Make any of the {11-20} planes. When the {1-100} plane is used as the main surface of the substrate, the {0001} plane,
One of the {11-20} planes becomes a cleavage plane perpendicular to the main surface of the substrate. Further, as the main surface of the substrate, {11-2}
When the {0} plane is used, {0001} plane, {1-10}
One of the 0 ° planes becomes a cleavage plane perpendicular to the main surface of the substrate. In this case, a resonator is formed by the two cleavage planes of the first semiconductor layer 1.

Further, the principal surface of the semiconductor substrate constituting the semiconductor laser is a {0001} surface, and a small surface other than the {0001} surface is provided on the surface of the substrate. The semiconductor layer 1 was used as a light emitting section (active layer). The small surface is a concept including a surface inclined with respect to the {0001} plane of the semiconductor substrate. As described above, a small surface other than the {0001} plane for providing the triaxial anisotropy may be provided on a part of the substrate.
Part of an S (Terraced Substrate) type semiconductor laser or the like can be configured.

The small face is defined as {1-100} face or {11}
A plane perpendicular to any one of the -20 ° planes may be used as the cleavage plane constituting the resonator. Again, in this case,
By using a {1-100} plane or a {11-20} plane perpendicular to the facet as a cleavage plane, a resonator can be constituted by two cleavage planes. Next, the structure of the above-described optical semiconductor device and its manufacturing method will be specifically described.

First Example First, as shown in FIG. 2A, TMGa is placed on an n-type GaN (1-100) substrate 11 having a (1-100) plane as a main surface.
(Trimethylgallium) is 10 to 100 μmol / min, for example, 45 μmol / min, and TMA1 (trimethylaluminum) is 10 to 100 μmol / min, for example, 45 μmol.
/ Min, 0.02 to 0.2 mol / min of ammonia (NH ₃ ),
For example, 0.1 mol / min, 0.1 to Si ₂ H ₆ 0001~
0.002 μmol / min, for example, 0.0007 μmol / min
And hydrogen as a carrier gas for 300 to 300 minutes.
0 sccm, for example, 1000 sccm, and the growth pressure is 70 to
760 Torr, for example, 100 Torr, and a growth temperature of 85
0 to 1100 ° C., for example, at 950 ° C., 10
0～5000Nm, preferably 2000 nm n-type is Al _0.1 Ga _{0 .9}
The N cladding layer 12 is grown.

Subsequently, TMGa was added in an amount of 10 to 100 μmol.
/ Min, for example, 45 μmol / min.
０0.2 mol / min, for example, 0.1 mol / min, and Si ₂ H ₆ from 0.0001 to 0.002 μmol / min, for example, 0.0
007 μmol / min, and flowing hydrogen as a carrier gas at a flow rate of 300 to 3000 sccm, for example, 1000 sccm,
The growth pressure is 70 to 760 Torr, for example, 100 Torr, and the growth temperature is 800 to 1,050 ° C., for example, 930 ° C.
In a state of 50 to 500 nm, preferably 100 nm
The n-type GaN optical guide layer 13 is grown.

Subsequently, 2.5 to 25 μmol of TMGa was added.
/ Min, for example, 10 μmol / min, and TMIn (trimethylindium) at 25 to 250 μmol / min, for example, 100 μmol / min.
μmol / min, 0.02-0.2 mol / min of ammonia,
For example, a flow rate of 0.1 mol / min, nitrogen as a carrier gas of 300 to 3000 sccm, for example, 1000 sccm is flowed, and a growth pressure of 70 to 760 Torr, for example, 100 T
orr and a growth temperature of 550 to 800 ° C., for example, 65
At 0 ° C., a Ga having a thickness of 1 to 20 nm, preferably 3 nm
_{A 0.9} In _0.1 N active layer 14 is grown.

Subsequently, TMGa was added in an amount of 10 to 100 μmol.
/ Min, for example, 45 μmol / min.
~ 0.2 mol / min, for example, 0.1 mol / min.
l / min, for example, 0.05 μmol / min, and 300 to 3000 sccm of hydrogen as a carrier gas, for example, 1 μmol / min.
At a growth pressure of 70 to 760 Torr, for example, 100 Torr, and a growth temperature of 800 to 1050 ° C.
For example, at a temperature of 930 ° C., a thickness of 50 to 500 nm,
Preferably, a 100 nm p-type GaN light guide layer 15 is grown.

Subsequently, TMGa was added in an amount of 10 to 100 μmol.
Per minute, for example, 45 μmol / min.
μmol / min, for example, 45 μmol / min, ammonia: 0.02 to 0.2 mol / min, for example, 01 mol / min, biscyclopentadienyl magnesium: 0.01 to 0.1 mol / min.
5 μmol / min, for example, 0.05 μmol / min, and hydrogen as a carrier gas flowing at 300 to 3000 sccm, for example, 1000 sccm, and a growth pressure of 70 to 760 Torr,
For example, 100 Torr and a growth temperature of 850 to 110
0 ° C., for example, at 950 ° C.,
A p-type Al _0.1 Ga _0.9 N cladding layer 16 of 00 nm, preferably 500 nm is grown.

In this case, the growth rate of the Al _0.1 Ga _0.9 N clad layers 12 and 16 is 0.6 to 5.5 μm / hour, typically 2.6 μm / hour. The growth rate of 13, 15 is 0.5 to 5.2 μm / hour, typically 2.4 μm / hour, and the growth rate of the Ga _0.9 In _0.1 N active layer 14 is _{0.1 to} 1.5 μm. / Hr, typically 0.6 μm / hr.

Next, the n-type GaN (1-100) substrate 11
A Ti / Au electrode 17 is provided as an n-side electrode on the back surface of the substrate, while a Ni / Au electrode 18 is provided as a p-side electrode on the p-type Al _0.1 Ga _0.9 N clad layer 16 and after appropriate element isolation, The semiconductor laser is completed by cleaving at the (0001) plane to form a resonator. In this case, since the (0001) plane is perpendicular to the (1-100) plane, which is the main surface of the substrate,
The pair of cleavage planes will act as a resonator.

In this first example, (1)
(-100) plane, n-type grown on it
The growth surfaces of the Al _0.1 Ga _0.9 N clad layer 12 to the p-type Al _0.1 Ga _0.9 N clad layer 16 are also (1-100) planes.
_{The 0.9} In _0.1 N active layer 14 receives a compressive stress in the (1-100) plane due to a difference in lattice constant between the active layer 14 and the n-type GaN optical guide layer 13, and thus becomes triaxial anisotropic.

That is, the in-plane atomic spacing in the first example is defined by the lattice constants 3.189 ° and 5.185 ° of the a-axis and c-axis of the n-type Al _0.1 Ga _0.9 N cladding layer 12, so that a The lattice constants of the axis and the c axis are 3.225 ° and 5.2
A compressive stress is applied to the Ga _0.9 In _0.1 N active layer 14 of 43 °, and the active layer 14 becomes triaxial anisotropic. Note that Ga _0.9 In _0.1 N, GaN,
And the energy band gaps of Al _0.1 Ga _0.9 N are 3.15 eV, 3.4 eV, and 3.7 eV, respectively.

When an in-plane compressive stress is applied to such a GaN-based semiconductor, as shown in FIG. 2 (b), the degeneracy of the HH and LH bands, which were the highest in energy and degenerate, is released. LH is at the highest level, and the transition between this LH and the conduction band causes laser oscillation, and the threshold current density is greatly reduced. In the first example, the substrate has a (1-100) plane as a main surface.
N (1-100) The substrate 11 is used, but (11-2)
A GaN substrate whose main surface is 0) may be used.
An AlN substrate or a SiC substrate having a (1-100) plane or a (11-20) plane as a principal plane may be used, and the principal plane is a (1-100) plane or a (11-20) plane.
This includes all planes that are crystallographically equivalent to the plane, and the same applies to the following examples of the present embodiment.

As a substrate on which the active layer and the cladding layer of the semiconductor laser are formed, other than GaN, other substrates such as AlN, SiC and the like may be used. For example, the GaN substrate in the device structure shown in FIG. 2A may be replaced with an AlN substrate, and the same structure as that shown in FIG. 2A may be provided thereon. 5-100nm thick on SiC base slope,
For example, the same structure as that shown in FIG. 2A may be provided thereon via an n-type AlN buffer layer of 20 nm.

As shown in FIG. 3, the AlN substrate 11a
If the resistance of the AlGaN cladding layer is considered to be high,
A structure in which an electrode 17a is connected to a part of 2 is adopted. AlN
The same applies when a buffer layer is used. They are,
The following example may be similarly adopted. In this embodiment and the following embodiments, as shown in FIG. 2C, the energy band gap of the active layer is smaller than the energy band gaps of the cladding layer, a guide layer described later, and a light confinement layer described later. .

Second Example Next, a second example of this embodiment will be described with reference to FIG.
First, as shown in FIG. 4 (a), on an n-type GaN (1-100) substrate 21 having a (1-100) plane as a main surface, TMGa is added at 2.5 to 25 μmol / min, for example, 10 μmol / min. Minutes, T
30 to 300 μmol / min, for example, 150 μmol
/ Min, 250 to 2500 μmol / min of TMIn, for example,
1000 μmol / min, 0.02-0.2 mol of ammonia
/ Min, for example, 01Mol / min, 0.1 to Si ₂ H ₆ 0001
~ 0.002 μmol / min, for example 0.0007 μmol
/ Min, and 300 to 30 nitrogen as a carrier gas.
At a flow rate of 00 sccm, for example, 1000 sccm, and a growth pressure of 70 sccm.
Up to 760 Torr, for example, 100 Torr and a growth temperature of 5
50 to 900 ° C., for example, at 700 ° C., 10
0～5000Nm, preferably 2000 nm n-type of Al _0.4 Ga _0.3
The In _0.3 N cladding layer 22 is grown.

Subsequently, TMGa was added in an amount of 5 to 50 μmol /
Min., For example, 20 μmol / min.
mol / min, for example, 50 μmol / min.
1500 μmol / min, for example, 660 μmol / min, and 0.02-0.2 mol / min of ammonia, for example, 0.1 mol
/ Min, 0.001 to 0.002 μmol of Si ₂ H ₆ /
Min, for example, 0.0007 μmol / min, and nitrogen as a carrier gas at 300 to 3000 sccm, for example, 1
5,000 sccm at a growth pressure of 70 to 760 Torr, for example, 100 Torr, and a growth temperature of 550 to 900 ° C., for example, 700 ° C., and n-type Al _0.15 Ga _0.65 having a thickness of 50 to 500 nm, preferably 100 nm. In _0.2 N light guide layer 2
Grow 3.

Subsequently, 2.5 to 25 μmol of TMGa was added.
/ Min, for example, 10 μmol / min.
0 μmol / min, for example, 100 μmol / min, and 0.02-0.2 mol / min of ammonia, for example, 01 mol / min.
And 300 to 3000 sc of nitrogen as a carrier gas.
cm, for example, 1000 sccm, and the growth pressure is 70-7.
60 Torr, for example, 100 Torr, and the growth temperature is 550.
To 900 ° C., for example, at 700 ° C., and a thickness of 1 to
A 20 nm, preferably 3 nm, Ga _0.9 In _0.1 N active layer 24 is grown.

Subsequently, TMGa was added in an amount of 5 to 50 μmol /
Min., For example, 20 μmol / min.
mol / min, for example, 50 μmol / min.
1500 μmol / min, for example, 660 μmol / min,
0.02 to 0.2 mol / min, for example, 0.1 mol
 / Minute, biscyclopentadienyl magnesium is added to 0.0
1 to 0.5 μmol / min, for example, 0.05 μmol / min,
And 300 to 3000 sc of nitrogen as a carrier gas.
cm, for example, 1000 sccm, and the growth pressure is 70-7.
60 Torr, for example, 100 Torr, and the growth temperature is 550.
To 900 ° C., for example, at 700 ° C.
~ 500 nm, preferably 100 nm p-type Al _0.15Ga_0.65In
_0.2The N light guide layer 25 is grown.

Subsequently, 2.5 to 25 μmol of TMGa was added.
/ Min, for example, 10 μmol / min.
μmol / min, for example, 150 μmol / min.
0 to 2500 μmol / min, for example, 1000 μmol / min.
, Ammonia at 0.02-0.2 mol / min, for example,
0.1 mol / min, 0.01 to 0.5 μmol / min of biscyclopentadienyl magnesium, for example, 0.05 mol / min.
mol / min and nitrogen as carrier gas from 300 to
With a flow rate of 3000 sccm, for example, 1000 sccm, a growth pressure of 70 to 760 Torr, for example, 100 Torr, and a growth temperature of 550 to 900 ° C., for example, 700 ° C.,
100-2000 nm, preferably 500 nm p-type Al _0.4 Ga
_{A 0.3} In _0.3 N cladding layer 26 is grown.

In this case, Al_0.4Ga_0.3In_0.3N Kula
The growth rate of the pad layers 22 and 26 is 0.2 to 3.0 μm /
Hour, typically 1.2 μm / hour, and_0.15Ga
_0.65In _{0, .2}The growth rate of the N light guide layers 23 and 25 is 0.3
５5.0 μm / hour, typically 1.8 μm / hour,
Furthermore, Ga_0.9In_0.1The growth rate of the N active layer 14 is 0.1 to
1.5 μm / hour, typically 0.6 μm / hour.

Next, n-type Ga having a surface of (1-100) plane
A Ti / Au electrode 27 is provided on the back surface of the N substrate 21 as an n-side electrode, while a Ni / Au electrode 28 is provided on the p-type Al _0.4 Ga _0.3 In _0.3 N clad layer 26 as a p-side electrode. After separation, the semiconductor laser is completed by cleavage along the (0001) plane to form a resonator. In this second example,
Because of the use of (1-100) plane as the substrate, also the growth surface of the n-type Al _0.4 Ga _0.3 In _0.3 N cladding layer 22 to p-type Al _0.4 Ga _0.3 In _{0 .3} N cladding layer 26 grown thereon (1
-100) plane, and the Ga _0.9 In _0.1 N active layer 24 is subjected to tensile stress, so that it becomes triaxial anisotropic.

That is, the in-plane atomic spacing in the second example is defined by the lattice constants of the a-axis and c-axis of the n-type Al _0.4 Ga _0.3 In _0.3 N cladding layer 22, 3.266 ° and 5.276 °. Therefore, the lattice constant of a-axis and c-axis 3. joined by 225Å and 5. tensile the Ga _0.9 in _{0 .1} N active layer 24 is 243Å stress, a three-axis anisotropy. Note that Ga _0.9 In _0.1 N
, Al _0.15 Ga _0.65 In _0.2 N and Al _0.4 Ga _0.3 In _0.3 N have energy band gaps of 3.15 eV,
3.4 eV and 3.6 eV.

As described above, when an in-plane tensile stress is applied to the GaN-based semiconductor, as shown in FIG. 4B, the degeneracy of the HH and LH bands, which are the highest in energy and degenerate, is reduced. It can be melted and separated, HH is at the top, and the energy difference between LH and HH can be made larger, so that the threshold current density can be further reduced. As described above, regarding the reduction of the threshold current density, the band structure of the valence band in FIG. 2 (b) due to the biaxial compressive stress in the growth plane is shown in FIG. 4 (b) due to the biaxial tensile stress in the plane. The band structure of the valence band is preferable because the energy difference between the top band and the second band can be increased. However, in the case of tensile stress, the possibility of cracks in the active layer is high. Therefore, the compressive stress is more desirable from the viewpoint of the element life.

In this second example, when an AlN substrate is used, the device structure shown in FIG.
The GaN substrate may be replaced with an AlN base, and the same structure as that shown in FIG. 4A may be provided thereon. When a SiC substrate is used, a 5 to 100 nm-thick, e.g.
The same structure as that shown in FIG. 4A may be provided thereon with a nm AlN buffer layer interposed therebetween.

[0075]Third example Next, referring to FIG. 5, a third example of the present embodiment will be described.
As will be explained, since the manufacturing conditions are exactly the same as in the first example,
The structure will be described. The element whose perspective view is shown in FIG.
TS type semiconductor laser, (0001) face as substrate
From the (11-21) plane to the step of the GaN substrate
(11-21) n-type GaN (000
1) The substrate 31 is used. This n-type GaN (0
001) On the substrate 31, just like the first example, the n-type
Al_0.1Ga _0.9N clad layer 12, n-type GaN light guide layer 1
3, Ga_0.9In_0.1N active layer 14, p-type GaN light guide layer 1
5 and p-type Al_0.1Ga_0.9N cladding layer 16 is grown sequentially
Let it.

Next, the Ni / Au electrode 18 is provided through the opening provided in the Ti / Au electrode 17 and the insulating film 33 of SiO ₂ or the like to appropriately separate the elements, and then cleaved on the (1-100) plane. By doing so, a TS type semiconductor laser using the pair of (1-100) cleavage planes 34 as resonators is completed. In this case, the main surface of the substrate is a (0001) plane perpendicular to the c-axis,
The light emitting portion, ie, the laser oscillation portion is actually (11-
21) is a plane parallel to the plane, and in this (11-21) plane, compressive stress is applied to become triaxial anisotropic, and FIG. 2 (b)
The threshold current density decreases because the degeneracy can be solved as in
Since the stress is applied to the (11-21) face 32,
The effect of the stress is smaller than in the first example, and the effect of reducing the threshold current density is inferior.

The small surface in this case is not limited to the (11-21) small surface 32. Also in this third example, the substrate is not limited to GaN and LiAlO ₃ ,
N or SiC may be used, and the configuration change accompanying the change of the material of the substrate is the same as the case of the replacement in the first example, and uses a semiconductor having the same composition as the second example. In this case, as in the second example, a tensile stress is applied to the active layer.

Fourth Example In the first to third examples described above, a binary compound substrate is used as the substrate. However, Al _0.1 Ga _0.9 N or Al
A mixed crystal substrate of _0.4 Ga _0.3 In _0.3 N or the like may be used. In this case, since the lattice matching between the Al _0.1 Ga _0.9 N cladding layer is formed on or Al _0.4 Ga _0.3 In _{0 .3} N cladding layer can be taken completely without impairment of crystalline growth layer .

As shown in FIG. 6A, a substrate used for forming another semiconductor laser is LiAl having a tetragonal structure.
An O ₂ substrate 35 may be used, an example of which will be described below. Note that LiAlO ₂ is called lithium aluminate. Therefore, next, a process of forming a semiconductor laser using the LiAlO ₂ substrate 35 will be described.

As the main surface of the LiAlO ₂ substrate 35, a {100} surface or a substrate turned off at a predetermined angle from the {100} surface, for example, within a range of ± 5 degrees is used. First, LiAl using an organic cleaning agent such as isopropyl alcohol or ethyl alcohol
The surface of the O ₂ substrate 35 is cleaned. Next, a LiAlO ₂ substrate 3 is placed on a susceptor in a growth furnace of a metal organic chemical vapor deposition apparatus (not shown).
5 is placed. Then, while replacing the atmosphere around the LiAlO ₂ substrate 35 with nitrogen, the pressure of the atmosphere was increased to 100 Ton.
Reduce pressure by rr.

Subsequently, the LiAlO ₂ substrate 35 is heated at a temperature 50 degrees higher than the growth temperature described later, whereby the elements on the surface of the LiAlO ₂ substrate 35 are sublimated to perform thermal cleaning. Thereafter, the LiAlO ₂ substrate 35 is, for example, 800 to 10
Reduce the temperature to 50 ° C and then add TM
Ga gas, ammonia gas, and Si ₂ H ₆ gas are introduced. TM
Ga is gasified by bubbling with a nitrogen gas in a thermostat, and the nitrogen gas is used as a carrier gas. Further, the Si element in Si ₂ H ₆ functions as an n-type dopant.

The flow rate of the TMGa gas is 10 to 100 μmol.
Set within the range of / min. Further, the flow rate of the ammonia gas is in the range of 2 × 10 ⁴ to 2 × 10 ⁵ μmol / min. Further, nitrogen gas is used in an amount of 0.3 to 3.0 μmol / min.
Set within the range. In this case, the flow rate of the TMGa gas is set to 4
5 μmol / min, flow rate of ammonia gas is 1 × 10 ⁵ μm
mol / min, the flow rate of nitrogen gas is set to 1.0 μmol / min, and the growth temperature is set to 930 ° C., Li
The growth rate of GaN on the AlO ₂ substrate is 2.4 μm / h.
In addition, according to the conditions within the ranges of the gas flow rate and the growth temperature described above, the growth rate of GaN is 0.5 to 5.2 μm / h.

Under such conditions, an n-type GaN buffer layer 36 having a thickness of, for example, 5 to 100 nm is grown on the LiAlO ₂ substrate 35. Then, under the same conditions as in the first example, n
Type Al _0.1 Ga _0.9 N clad layer 12, GaN light guide layer 13,
Ga _0.9 In _0.1 N active layer 14, p-type GaN light guide layer 15, p
-Type Al _0.1 Ga _{0 .9} N cladding layer 16 in this order. In addition,
Magnesium (Mg) is used as a p-type dopant.

The conditions for forming these layers, the film thickness, and the source gas are the same as in the first example. Next, after removing the LiAlO ₂ substrate 35 from the growth furnace, the n-type Al _0.1 Ga _0.9 N clad layer 1 is removed.
2 is exposed, a Ti / Au electrode 37 is formed as an n-side electrode on a part of the n-type Al _0.1 Ga _0.9 N clad layer 12, and further on the p-type Al _0.1 Ga _0.9 N clad layer 16. Has p
A Ti / Au electrode 18 is formed as a side electrode. And LiAl
O ₂ substrate 35 and a layer 36,12～16 and electrodes thereon suitably isolation to complete the semiconductor laser.

By the way, as shown in FIG. 7, tetragonal Li
When hexagonal GaN is grown on the {100} plane of the AlO ₂ substrate 35, the a-axis of LiAlO ₂ and the c-axis of GaN become parallel, and LiAlO ₂
Is parallel to the a-axis of GaN. As a result, on the {100} plane of the LiAlO ₂ substrate 35, GaN grows with the (1-100) plane facing upward, so that the lower ground of the Al _0.1 Ga _0.9 N clad layer 12 is (1-100) plane.

Therefore, as in the first example, Al _0.1 Ga
_0.9 N clad layer 12, GaN light guide layer 13, Ga _0.9 In
_0.1 N active layer 14, p-type GaN light guide layer 15, p-type Al _0.1
The growth surface of the Ga _0.9 N cladding layer 16 is also a (1-100) plane, and the Ga _0.9 In _0.1 N active layer 14 is an n-type GaN optical guide layer 13.
Due to the difference in lattice constant between the first example and the second example, a compressive stress is applied in the (1-100) plane, so that the crystal has triaxial anisotropy as in the first example.

As shown in FIG. 7, tetragonal LiAlO ₂
Is an inter-atomic distance L _{1 in} the a-axis direction of 5.1687 °, and an inter-atomic distance L _{2 in} the c-axis direction of tetragonal LiAlO ₂ is 6.2679 °.
The inter-atomic distance L _{3 in} the a-axis direction of hexagonal GaN is 3.189 °, and the inter-atomic distance L ₄ in the c-axis direction of hexagonal GaN is 5.185 °. Therefore, considering the interatomic distances and the directions of the a-axis and c-axis,
The mutual lattice mismatch between the GaN buffer layer and the LiAlO ₂ substrate is as follows.

In the c-axis direction of the GaN buffer layer 36,
The lattice mismatch between the GaN buffer layer 36 and the LiAlO ₂ substrate 35 is
It is small as in the following equation (1). (C _GaN −a _{LiAlO 2} ) / a _{LiAlO 2} = 3.2 × 10 ⁻³ (1) where c _GaN is the interatomic distance of GaN in the c-axis direction, a
_LiAlO2 is a inter-axis direction of the interatomic distance of LiAlO _2.

In the a-axis direction of the GaN buffer layer, the lattice mismatch between the GaN buffer layer and the LiAlO ₂ substrate is small as in the following equation (2). (2 × a _GaN− c _LiAlO 2) / c _{LiAlO 2} = 1.8 × 10 ⁻³ (2) where a _GaN is the interatomic distance of GaN in the a-axis direction, c
_LiAlO2 is c between axis of atomic distances LiAlO _2.

As described above, when the lattice mismatch between the LiAlO ₂ substrate 35 and the GaN layer 36 is small, either the {100} plane or the plane which is off by 0 to 5 degrees from that plane is used as the main surface of the LiAlO ₂ substrate 35. When the GaN layer 36 is formed on the main surface, Ga
The N layer 36 is less likely to crack due to thermal expansion. In this case, the c-axis of the GaN layer 36 is inclined by 0 to 5 degrees from the main surface of the LiAlO ₂ substrate 35, and the GaN layer 36 is strained in a plane not perpendicular to the c-axis. As a result,
The strain applied to the GaN layer 36 indicates triaxial anisotropy, whereby the double degeneracy of HH and LH in the valence band of the energy band structure is released, and the threshold current density of the semiconductor laser decreases.

When a rocking curve showing the intensity distribution of diffraction of X-ray irradiation of the single crystal GaN layer grown on the (1-100) plane was measured, as shown in FIG. In the above description, the formation of a GaN film on a LiAlO ₂ substrate has been described. However, as shown in FIG.
The same crystal structure is obtained when the Al _x Ga _{1 -xy} In _y N layer is formed directly on the LiAlO ₂ substrate 35. That is,
The {100} plane or a plane that is 0 or 0 to 5 degrees off from the {100} plane is defined as the main surface of the LiAlO ₂ substrate 35, and the n-type Al _0.4 Ga _0.3 In _0.3 N clad layer 1
2. n-type Al _0.15 Ga _0.65 In _0.2 N optical guide layer 13, Ga _0.9 In
_0.1 N active layer 14, p-type Al _0.15 Ga _0.65 In _0.2 N optical guide layer 1
15, an n-type Al _0.4 Ga _0.3 In _0.3 N clad layer 16 may be formed in order, and a semiconductor laser may be formed from these layers. The growth conditions, film thickness, and the like in this case are the same as those in the second example.

By the way, Al _x Ga _1-xy In _y N (0 ≦ x ≦
1, 0 ≦ y ≦ 1), the formula (1) of the inter-atomic distance La ₁ in the a-axis direction
Indicated by 1), c between axis of atomic distance La ₂ of LiAlO ₂ is represented by the formula _{(12), Al x Ga 1} -xy In y N in the a-axis direction and Li
The c-axis direction of AlO ₂ is parallel. Al _x Ga _1-xy In _y
N is represented by Expression (13) of the interatomic distance Lc ₁ in the c-axis direction,
The inter-atomic distance Lc _{2 in} the a-axis direction of GaN is represented by equation (14), and the c-axis direction of Al _x Ga _1-xy In _y N and the a-axis direction of LiAlO ₂ are parallel.

[0093] La₁= Xa_AlN+ A_GaN-Xa_GaN-Ya_GaN+ Ya_InN … (11) La_Two= C_LiAlO2 … (12) Lc₁= Xc_AlN+ C_GaN-Xc_GaN-Yc_GaN+ Yc_InN ... (13) Lc_Two= A_LiAlO2 ... (14) In those equations, a_AlNIs the interatomic distance in the a-axis direction of AlN
Separation, a_GaNIs the interatomic distance in the a-axis direction of GaN,_InNIs In
Distance between atoms in the a-axis direction of N, c_LiAlO2Is LiAlO_TwoC-axis direction
The interatomic distance, and c_AlNIs the c-axis direction of AlN
Distance between atoms, c _GaNIs the interatomic distance in the c-axis direction of GaN,
c_InNIs the interatomic distance in the c-axis direction of InN, a _LiAlO2Is LiAl
O_TwoIs the distance between atoms in the a-axis direction.

The composition ratio x, y of Al _x Ga _1-xy In _y N
, The equations (15) to (18) are obtained under the condition that the lattice mismatch is 2 × 10 ^-2 %, and when these are drawn on the x and y coordinates, the conditions of the equations (15) to (18) are satisfied. x, y
Is a region indicated by oblique lines in FIG. 9. If the composition ratio of x and y indicated by oblique lines is selected, the crystallinity is good and cracks due to thermal expansion and the like are less likely to occur in the crystal. Note that the expression (1)
5) is not shown in FIG. 9 since y becomes negative when x ≦ 1.

[0095]

(Equation 1)

(Other Examples) In the first to third examples described above, the (1-100) plane or the
Although a just surface such as the (11-21) plane is used, the (1-100) plane or the (1
A substrate in which the 1-21) plane is turned off within the range of the off angle θ (0 ° ≦ θ ≦ 10 °) may be used.

Further, in the above example, Ga _0.9 In _0.1 N is used as the active layer, but the mixed crystal ratio is changed to Al _x Ga _{1 -xy} In _y N (0 ≦ x ≦ 1, 0 ≦ y ≦
It may be changed within the range of 1), and accordingly, the mixed crystal ratio of the optical guide layer and the cladding layer is changed to Al _a Ga.
It may be changed within the range of _1-ab In _b N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1).

Although the light guide layer is used in the above example, it is not always necessary, and a hetero junction may be directly formed by the cladding layer and the active layer.
The light guide layer and the cladding layer do not necessarily have to be vertically symmetrical, and Al _a Ga _1-ab In _b N
May be used. Also, the raw materials used in the above examples are not limited to the above raw materials, and the organic metal raw materials are ethyl-based instead of methyl-based, that is, TEGa (triethylgallium), TEAl (triethylaluminum),
And TEIn (triethylindium) may be used, and N ₂ H ₄ , (CH ₃ ) ₃ CNH ₂ , C ₂ H ₅ N ₃ , or CH ₂ may be used instead of ammonia as a nitrogen (N) source. ₃ NH
· NH ₂ may also be used.

Further, the impurity material is also Si for n-type.
Instead of ₂ H _6, may be used SiH ₄ or CH ₃ SiH _3, In place of bis (cyclopentadienyl) magnesium as a p-type [(C ₅ H _{5) 2} Mg], (CH ₃ C ₅ H ₄ ) ₂ M
_{g, (C 5 H 5 C} 5 H 4) 2 Mg, (iC 3 H 7 C 5 H 4) 2 Mg, or, (nC
₃ H ₇ C ₅ H ₄ ) ₂ may be used. (Second Embodiment) FIG. 10 is a perspective view showing a basic structure of a surface emitting semiconductor laser of the present embodiment. FIG. 11 is a view showing the crystal orientation of the active layer of the present invention, and shows the relationship between the crystal orientation of the active layer of the semiconductor laser shown in FIG. 10 and the coordinate axes.

In the first configuration of the present invention, referring to FIG. 10, active layer 42 formed above substrate 41 is formed of a hexagonal semiconductor layer having a c-axis in its plane. That is, as shown in FIGS. 10 and 11, when the xz plane is taken in the main surface of the active layer 42 and the y axis is taken in the vertical direction of the active layer 42, the c-axis of the hexagonal semiconductor crystal forming the active layer 42 is Direction, that is, the <0001> direction,
Place it towards the axis.

By including the c-axis in the plane of the active layer 42, the polarization plane of the oscillation light is defined as described below. The crystal orientations of the x and y axes are not particularly limited. For example, the <11-20> direction is set to the x axis in the plane of the active layer 42 and the <1-100>
The azimuth can be the y-axis in the thickness direction of the active layer 2.

Hereinafter, the reason why the polarization plane of the oscillation light is defined in the present embodiment will be described. First, the case where there is no distortion in the active layer will be described. FIG. 12 is an energy band structure diagram of GaN, showing a band structure of a hexagonal semiconductor. As shown in FIG. 12, in the valence band VB of GaN, three bands of HH, CH and LH exist near the bottom of the forbidden band near the electron wave vector k = 0.

Here, when there is no strain in GaN, at the wave vector k = 0, the valence band having the highest energy is the HH band, the one having the next highest energy is the LH band, and the lowest energy is the LH band. These are CH bands. Note that these HH, LH and CH bands correspond to c
When taking axially Z axis of XYZ3 axis orthogonal coordinate, the two having a polarization direction perpendicular to the c axis p orbitals p _x and p
_It is expressed as follows using _y and an orbital function p _z having polarization in the c-axis direction.

Hp band; (p _x + p _y ) / √2 LH band; (p _x -p _y ) / √2 CH band; p _z Since the HH band is closest to the bottom of the forbidden band, the conduction band CB For the spontaneous emission from the valence band VB to the valence band VB, the emission transition to the HH band has priority. This HH band consists of a coupled state of p orbitals and is symmetric about the c axis. For this reason, light emission accompanying spontaneous emission of GaN has a polarization state in which the electric field oscillates perpendicularly to the c-axis. Further, the transition probability of generating such polarized light is equivalent to the rotation of the vibration azimuth around the c-axis. Although the above description has been made with reference to GaN, the same applies to hexagonal semiconductor crystals. Incidentally, the zinc blende type semiconductor crystal is triaxially isotropic, so that the optical characteristics are isotropic.

In a conventional surface emitting semiconductor laser having a vertical cavity, as shown in FIG.
Oscillation light travels along the c-axis 104 because the oscillation light is formed perpendicular to the light-emitting element 04. Therefore, the polarization plane of the oscillation light becomes the c plane,
The electric field oscillates perpendicular to the c-axis 104. As a result, due to the symmetry of the polarization of the spontaneous emission light around the c-axis, oscillation light oscillating in any direction in the XY plane is equally generated. Therefore, the polarization plane of the oscillation light is not fixed, and the oscillation becomes unstable.

On the other hand, in the present embodiment, as shown in FIG. 10, since the active layer 42 has a c-axis in the plane, the traveling direction of the oscillation light is perpendicular to the c-axis. As described above, when HH is at the band edge, the oscillation direction of the electric field of the spontaneous emission light is perpendicular to the c-axis. Therefore, the oscillation direction of the electric field of the oscillation light is in both the c-axis and the traveling direction of the oscillation light. , That is, a direction that is uniquely defined in a direction included in the active layer plane and perpendicular to the c-axis.

Therefore, in the surface emitting semiconductor laser of this configuration, the electric field direction of the oscillating light traveling perpendicular to the active layer is fixed to the direction perpendicular to the c-axis. In the surface-emitting semiconductor laser, since the resonator is in the film thickness direction, the polarization direction determined by the top band (the direction of the electric field vector of light emission)
Must be in the active layer plane. That is, the polarization of the top band that determines the direction of the electric field vector of light emission needs to be in the plane of the active layer.

Next, the PL (photoluminescence) emission wavelength of the active layer and its polarization plane direction will be described. FIG.
FIG. 3 is a graph showing the PL emission characteristics of the active layer of the present invention when HH is at the band edge. It shows the calculated value of the emission intensity. The parameter in FIG. 13 is the azimuth of the plane of polarization of the PL light, that is, the angle θ between the vibration direction of the electric field on the active layer surface and the c-axis. In addition,
The following description is applicable not only to GaN but also to hexagonal semiconductor crystals.

As shown in FIG. 13, when the PL light emission of the active layer is divided into polarization planes, that is, the polarization plane of the electric field and the wavelength, the polarization plane of the PL light is orthogonal to the c-axis (90 in FIG. 13).
(Indicated by °), the PL emission spectrum intensity of the active layer becomes maximum. The wavelength corresponding to this maximum intensity is about 366 nm, and this wavelength corresponds to light emission due to the transition from the conduction band CB to the valence band VB to the HH band as shown in FIG. On the other hand, when the plane of polarization of the PL light is parallel to the c-axis (indicated by 0 ° in the figure), the emission intensity is small, and the maximum wavelength of the spectrum is as short as about 360 nm. This is because, by changing the polarization plane of the PL emission from a polarization plane perpendicular to the c-axis to a polarization plane parallel to the c-axis, the PL emission changes from the emission due to the transition to the HH band to the emission due to the transition to the CH band. Indicates that it has been migrated.

That is, the transition to the HH band composed of the p orbit polarized in the x-axis direction emits only light whose polarization plane is perpendicular to the c-axis, whereas the CH band is shifted from the p orbit polarized in the z-axis direction. Therefore, emission of light having a plane of polarization parallel to the c-axis is possible only by transition to the CH band. Further, in the present embodiment, when the polarization plane and the wavelength of the photoluminescence light of the semiconductor layer 2 are selected so that the photoluminescence light intensity is maximized, the wavelength of the photoluminescence light and the resonance wavelength of the optical resonator are changed. Match. The energy of light of this wavelength is equal to the photoenergy of light emission accompanying the transition of electrons to the HH band. Therefore, by oscillating at such a wavelength, oscillating light can be limited to only light emission due to the transition of electrons to the HH band. In this case, since the light emission accompanying the transition to the CH band having the polarization plane parallel to the c-axis cannot be mixed, the fluctuation of the polarization plane of the oscillation light can be reliably prevented.

The resonance wavelength does not need to be a wavelength at which the maximum intensity is strictly obtained. For example, mainly HH
The light emission accompanying the transition of the electron to the band occurs, and the light emission accompanying the transition to the CH band is small.
Any wavelength may be used as long as the wavelength is close to the maximum intensity to the extent that the oscillation mode can be prevented from changing from oscillation due to the transition of electrons to the band to oscillation due to the transition of electrons to the CH band.

Next, the case where there is a strain in the active layer will be described. FIGS. 14A to 14E are diagrams illustrating the strain dependence of the energy band of GaN, and show the calculated values of the energy of the valence band of GaN having strain. Referring to FIG. 11, the strain in the <0001> direction is ε _z , the strain in the <11-20> direction is ε _x , and the strain in the <1-100> direction is ε _y , and the respective strain values Indicates that the state of compressive strain is negative and the state of tensile strain is positive.

FIG. 14A shows a case where ε _z = 0 and ε _x is changed. Here, ε _y is a state where there is no constraint because y is the growth direction. That is, it is a result of calculating a change in valence band energy when uniaxial strain is applied in the <11-20> direction of the crystal. Same way, FIG. 14 (b), the epsilon _z 0.
This is the case where a tensile strain of 5% is added and ε _x is further added. 14 (c) and (d) show that 0.5% is added to ε _z , respectively.
And 1.0% compressive strain and ε _x . Note that there is no constraint on ε _y .

Referring to FIGS. 14A to 14C, when the strain ε _x is compressed and ε _z is compressed at 1.0% or more, the X or Z branch composed of the p orbitals has the energy band structure. The valence band is located at the bottom of the forbidden band (ie, at the top of the valence band). Therefore, the emission transition from the conduction band preferentially transitions to the X or Z branch, so that when X is above, the polarization perpendicular to the c-axis is the same as the emission without distortion described above. Only light having a surface oscillates. When Z is a band edge, light parallel to the c-axis oscillates.

[0115] Meanwhile, referring to FIG. 14 (d), the strain epsilon _z is 1
% Or more and ε _x is a tensile strain, X
And the Z branch has higher energy than the Y branch. Therefore, regarding the transition of electrons from the conduction band,
The light that oscillates on the plane of polarization parallel to the c-axis occurs with priority given to the transition to the Z branch. As described above, since the surface emitting semiconductor laser has a resonator perpendicular to the active layer, the electric field vector needs to be within the active layer plane. Therefore, it is necessary that the polarization of the top band wave function that determines the electric field vector is in the plane of the active layer. That is, when a structure as shown in FIG. 11 is manufactured, since the Y direction becomes a resonator, Y does not oscillate in the top band.

FIG. 14E shows that when ε _y is in an unconstrained state, ε _z = ε _x , in other words, <000
This is a calculated value of the energy band of the valence band when in-plane biaxial strain is applied to the plane including <1> and <11-20>. X has the highest energy with respect to the in-plane compression strain, and in this case, oscillating light having an electric field direction in the a-axis direction is generated. When the traveling direction of the light is in the polarization direction of the Y branch, CH
Oscillation occurs based on the transition to the band.

As described above, when the active layer has a distortion, the oscillating light has a polarization plane perpendicular to the c-axis and a polarization plane parallel to the c-axis. However, in each case, the polarization plane of the oscillating light is uniquely determined by the optical axis of the optical resonator and the crystal axis direction. Therefore, the polarization plane of the surface emitting semiconductor laser is predetermined and the polarization plane does not change. by the way,
In the configuration shown in FIG. 10, as the active layer 42, GaN
Quantum well layer containing Mn, lnGaN or AIGalnN (M
QW) or a single layer made of GaN, lnGaN, or AIGalnN.

Further, as the substrate 41 shown in FIG.
A SiC substrate having the (11-20) plane as a main surface may be used. Further, a SiC substrate having a (1-100) plane as a main surface or a sapphire substrate having a (1-102) plane as a main surface may be used. Further, on the main surface of the substrate 41, a first barrier layer 47 of the first conductivity type, an active layer 42, and a second barrier layer 48 of the second conductivity type are sequentially grown, thereby forming a double hetero junction. The structure is configured. When a reflection surface is formed above or below the double hetero junction structure, the first barrier layer 47, the active layer 42, and the second barrier layer 48 can be configured as an optical resonator. First and second barrier layers 4
The constituent material of 7 and 48 is AIGaN, and the active layer 42
From a single layer of AIGaN or GaN or InGaN, or a multiple quantum well layer containing such a material,
A surface emitting semiconductor laser having an active layer 42 made of a GaN-based semiconductor whose axis is in the plane is realized.

Next, this embodiment will be further described with reference to the drawings. The inventor of the present application measured the PL emission spectrum of the active layer 42, and found that the relationship between the PL emission wavelength and the polarization plane was such that the emission due to the transition from the conduction band to the HH band and the emission from the conduction band to the CH band. The following experiment clarified that it can be explained by the light emission due to the transition to.

First, the SiC having the (1-100) plane as the main surface
An undoped GaN thin film was deposited on the base plate by using the well-known MOVPE (metal organic vapor phase epitaxy) method, and the photoluminescence light intensity with respect to the polarization plane direction and wavelength of the photoluminescence light was measured. FIG.
5 and FIG. 16 show the results. FIG. 15 is a PL emission spectrum of the active layer 42 of the present embodiment,
Represents photoluminescence light having an electric field vector perpendicular to the c-axis, and B represents photoluminescence light having an electric field vector parallel to the c-axis. FIG. 16 is a graph showing the dependence of the PL emission intensity of the active layer of the present invention on the polarization plane. The maximum intensity of the PL emission when the polarization plane is fixed (hereinafter referred to as “peak intensity”) changes depending on the polarization plane. Yoko is represented. In FIG. 16, C represents an experimental value, and D represents a calculated value.

Referring to FIG. 15, the intensity A of photoluminescence light having a plane of polarization perpendicular to the c-axis has a strong maximum near 366 nm. On the other hand, the intensity B of the photoluminescence light having a polarization plane parallel to the c-axis has a weak maximum near 362 nm, which is a shorter wavelength. The wavelength at which these maxima appear and the magnitude of the maxima are in good agreement with the calculated values shown in FIG.

Next, as shown in FIG. 16, the peak intensity of PL emission becomes maximum when the polarization plane is perpendicular to the c-axis, and becomes minimum when the polarization plane is parallel to the c-axis. This experimental value C is
It matches well with the calculated value D. This means that the calculation results in FIG. 13 reproduce the experiment well. FIG.
FIG. 1 is a cross-sectional view of a device that further embodies the present embodiment, and is a surface-emitting semiconductor laser having a vertical resonator.

A 50-nm-thick GaN buffer layer 52 grown at a low temperature by MOVPE on a substrate 41, for example, a SiC base slope 41 having a (11-20) plane as a main surface, and a 0.5 μm-thick layer. N-type GaN contact layer 49 having a thickness of 1 μm
Si-doped n-type Al _0.1 Ga _0.9 N barrier layer 47, thickness 0.1 μm
An undoped GaN active layer 42, a 1 μm thick Mg-doped p-type Al _0.1 Ga _0.9 N barrier layer 48, and a p-type GaN contact layer 51 are sequentially grown from below.

Subsequently, a 30 nm thick SiO ₂ film and a 30 nm thick
Al ₂ O ₃ films are alternately deposited in layers of 20 layers each, and the multilayer film is patterned by photoresist lithography to form a DBR mirror 43 having a circular or square planar shape.
To form The DBR mirror 43 includes the n-type contact layer 4
A vertical optical resonator having a wavelength of 366 nm is formed using the interface between the substrate 9 and the substrate 41 as a reflection surface.

Next, each layer in a region on one side of the DBR mirror 43 is etched by a reactive ion etching (RIE) method, thereby exposing a part of the n-type contact layer 49. Thereafter, an electrode 50a made of Ti having a thickness of 100 nm is formed on the exposed surface of the n-type contact layer 49, and an electrode 50b made of Ni having a thickness of 100 nm is formed on the p-type contact layer 51. Further, the back surface of the substrate 41 is polished to form an optical window through which light is emitted, thereby completing a surface emitting semiconductor laser.

In such a surface emitting semiconductor laser, the light whose direction perpendicular to the c-axis of the substrate 41 becomes the vibration direction of the electric field is oscillated and the polarization plane is fixed, so that the laser light whose polarization direction is specified in advance is stabilized. Can be oscillated. Another example of the surface emitting semiconductor laser of the present embodiment is one in which the active layer has a multiple quantum well layer structure. A 0.5 nm thick AIN buffer layer 42 grown at a low temperature and a 0.5 μm thick n-type GaN contact layer 49 are grown on a SiC substrate 41 having a (11-20) plane as a main surface by MOVPE. , 1μm thick
Si-doped n-type Al _0.1 Ga _0.9 N barrier layer 47, In _0.15 Ga _0.85 N
An active layer 42 composed of multiple quantum well layers in which well layers and ln _0.05 Ga _0.95 N barrier layers are alternately layered by 10 layers each, and a thickness of 1
Mg-doped p-type Al _{0. 1} Ga _0.9 N barrier layer 48 [mu] m, and p-type
The GaN contact layer 51 is deposited in this order. And
The surface-emitting semiconductor laser is manufactured through the same steps as in the above-described embodiment.

In the above-described surface emitting semiconductor laser, (1-
By using a substrate having a (100) plane or a (11-20) plane as a main surface, light deflection is made uniform. It is possible to adopt a structure in which a light receiving element is also mounted on a substrate constituting such a surface emitting semiconductor laser. FIG.
FIG. 18A is a sectional view showing an optical device on which a surface emitting semiconductor laser (light emitting element) and a photodiode (light receiving element) are mounted, and FIG. 18B is a plan view showing the optical device.

In FIGS. 18A and 18B, the SiC substrate 5
On the (1-100) plane or (11-20) plane, which is the principal plane of No. 3, an AlN high-temperature buffer layer 54 having a thickness of 50 nm, a mirror layer 55 having a multilayer structure, and an n-type barrier layer having a thickness of 1 μm 56,
An undoped lower optical confinement layer 57 having a thickness of 500 nm, an undoped MQW active layer 58, a p-type barrier layer 59, an undoped upper optical confinement layer 60 having a thickness of 500 nm, and a film thickness of 5
A 0 nm GaN contact layer 60a is sequentially stacked by MOVPE.

The mirror layer 55 is made of Al _0.4 Ga _0.6 having a thickness of 40 nm.
It is formed by alternately stacking N layers and Al _0.1 Ga _0.9 N layers having a thickness of 40 nm for 30 periods. Further, the MQW active layer 58
Is to form a 4 nm thick In _0.2 Ga _0.8 N well layer with a 4 nm thick In _0.05 Ga.
It has a structure sandwiched by Ga _0.95 N barrier layers. The lower and upper light confinement layers 57 and 60 are each formed of GaN.

Further, n-type and p-type barrier layers 56 and 59
Are each made of Al _0.1 Ga _0.9 N, and the n-type barrier layer 56 has an impurity concentration of 2 × 10 ¹⁸ atoms / cm ³ ,
The p-type barrier layer 59 is doped with Mg at an impurity concentration of 1 × 10 ¹⁷ atoms / cm ³ . The contact layer 60a on the p-type barrier layer has 1 × 10 ¹⁸ atoms /
Mg is doped in cm ³ .

A plurality of layers from the n-type barrier layer 56 to the p-type barrier layer 59 are composed of SCH (separate confinement heteros).
tructure) structure. The compound semiconductor layer thus laminated is subjected to patterning a plurality of times as shown in FIG.
It is processed into a sectional structure and a planar structure as shown in (a) and (b). That is, the surface emitting semiconductor laser 66 and the light receiving element 67 have the same shape,
From a to the upper portion of the n-type barrier layer 56, a cylindrical portion 62 having a diameter of 20 μm is formed. Further, from the lower portion of the n-type barrier layer 56 to the upper portion of the mirror layer 55, a flange portion 63 extending outward from the cylindrical portion is formed. ing. Since the mirror layer 55 is undoped and has a high resistance, the columnar portion 62 and the flange portion 63 are electrically separated from the compound semiconductor layer in other regions via a substantially cylindrical groove 61.

Then, the contact layer 60a of the columnar portion 62
Light emitting window 64a having a diameter of about 10 μm
An n-type barrier layer 56 of the flange portion 63 is connected to a cylindrical portion 62.
Is connected to an n-side electrode 65 made of Ni which does not come into contact with. The above-described cylindrical portion 62 and the n-type barrier layer 5 thereunder
6 forms a resonator in the film thickness direction.

As shown in FIG. 18B, a plurality of, for example, four, photodiodes 67 are formed around the surface emitting semiconductor laser 66 at a distance. An optical device having such a surface emitting semiconductor laser 66 and a photodiode 67 is attached to, for example, a magneto-optical disk device. In the surface-emitting semiconductor laser 66, a positive bias voltage 68 is applied to the p-side electrode 64 and the n-side electrode 65, and a threshold current is supplied even if the voltage is small. In the photodiode 67, a reverse bias voltage is applied to the p-side electrode 64 and the n-side electrode 65, so that the current flowing through the detection circuit 69 increases due to the amount of light incident on the photodiode 67.

In this case, the surface emitting semiconductor laser 66 oscillates and irradiates light through the window 64a, and irradiates the magneto-optical disk through a diffraction grating, a lens, and the like (not shown).
The light reflected by the magneto-optical disk is input to four light receiving elements 67 through a lens and a deflection prism. In the surface emitting semiconductor laser 66, as described above, the substrate 4
1 oscillates light whose vertical direction is the vibration direction of the electric field and the polarization plane is fixed, so that the polarization planes of the laser light are aligned. Moreover, the laser light reflected by the magneto-optical disk enters the photodiode 67 having the same polarization plane.

As described above, since the surface emitting semiconductor laser 66 and the photodiode 67 formed on the same substrate have polarization planes, the write optical element and the read optical element of the magneto-optical disk device are integrated. Can be
The miniaturization and manufacturing efficiency of those devices are improved. As described above, according to the present embodiment, in the vertical cavity surface emitting semiconductor laser having the resonance axis perpendicular to the active layer, the polarization plane of the oscillation light is uniquely defined by the crystal orientation of the active layer. It is possible to provide a vertical cavity surface emitting semiconductor laser having a stable operation characteristic in which the polarization direction of the oscillating light can be determined in advance and the fluctuation of the polarization direction is small, which contributes to the improvement of the performance of the information processing apparatus. But big.

The active layer 58 is made of GaN, InGaN, AlGa
N or AlGaInN.
The barrier layers 57 and 59 made of semiconductor are made of GaN, InGaN, Al
It may be made of GaN or AlGaInN. However, when the active layer 58 and the barrier layers 57 and 59 are made of the same material, it is necessary to select a composition ratio at which the energy band gap of the active layer 58 is smaller than that of the barrier layers 57 and 59.

The substrate material is silicon carbide (Si)
Sapphire may be used in addition to C). (Third Embodiment) The conventional light emitting diode is circularly polarized with respect to the light emission direction. Therefore, when it is desired to obtain linearly polarized light, it is possible to obtain linearly polarized light by passing through a polarizer such as a polaroid. I was

When a three-dimensional image is displayed using linearly polarized light, a right-eye image and a left-eye image are displayed with lights having different polarization directions, and the right-eye polarizers having different polarization directions are displayed. The image is recognized as a stereoscopic image by observing through a polarizer for the left eye and a left-eye polarizer. In particular, in the case of a large stereoscopic image display device, a projection method is adopted. However, when trying to obtain linearly polarized light using a conventional light emitting diode, there is a problem that the number of components is increased because a polarizer is required, and a step of combining the light emitting diode and the polarizer is required. Therefore, there is a problem that the production cost is high.

Further, since circularly polarized light is converted into linearly polarized light in a specific direction via a polarizer, light having a polarization direction different from the polarization direction of the polarizer cannot be taken out and is wasted. There's a problem. In addition, in the case of a large stereoscopic display device, since the projection method is used, the display image becomes very difficult to see in a bright place and cannot be practically used as in the case of the conventional projection method display device. is there.

FIG. 19 is an explanatory diagram of the basic configuration of the present embodiment. Referring to FIG. 19, means for solving the problem in the present invention will be described. In the present embodiment, FIG.
As illustrated in (a) and (b), the light emitting diode 70 is characterized in that the c-axis direction of the wurtzite compound semiconductor crystal constituting the light emitting diode 70 is substantially orthogonal to the light emission direction. .

When a wurtzite compound semiconductor such as GaN is used, the wurtzite compound semiconductor is GaAs.
Unlike the other III-V group compound semiconductors such as wurtzite type compound semiconductors, light emission from such a wurtzite type compound semiconductor is HH (Heavy Hole) or LH in the valence band from the conduction band.
(Light Hole)
Since the band is related to the axial direction, the c-axis direction, ie, <
0001> light polarized in a direction perpendicular to the direction appears strongly,
Conversely, since light polarized parallel to the c-axis direction hardly appears, linearly polarized light can be obtained without using a polarizer.

In the present invention, the expression that the c-axis direction is substantially orthogonal to the light emission direction means that the c-axis and the emission direction of the light having the highest intensity are in a range of ± 5 ° in addition to those in which the c-axis and the emission direction of the light having the highest intensity are purely orthogonal. Includes angles. In addition, the present embodiment is characterized in that the c-axis direction of the wurtzite compound semiconductor crystal is aligned with the crystal growth direction.

As a growth substrate, sapphire of $ 000
1｝ plane, {11-20} plane, 6H-SiC ｛000
When the {1} plane or the {111} plane of the spinel is used, the crystal growth direction of the wurtzite type compound semiconductor crystal is the c-axis direction, so that the light is parallel to the active layer as shown in FIG. , Linearly polarized light is obtained. In this specification, “1 bar” or “2 bar” is used.
For convenience, the crystal orientation such as “bar” is “−1” or “−”.
2 "etc.

Further, the present embodiment is characterized in that the c-axis direction of the wurtzite compound semiconductor crystal is substantially orthogonal to the crystal growth direction. As the main surface of the growth substrate, the r-plane of the sapphire substrate, that is, the {1-102} plane or 6H-
When the {1-100} plane or the {11-20} plane of SiC is used, the crystal growth direction of the wurtzite compound semiconductor crystal is substantially parallel to the c-axis direction, and as shown in FIG. By extracting light perpendicularly to the active layer, linearly polarized light is obtained, and light from a wide surface becomes polarized light, so that a large light emitting area can be obtained.

The present embodiment is characterized in that the wurtzite compound semiconductor is a III-V group compound semiconductor made of a group III nitride. Thus, GaN having a stable crystal structure as a wurtzite compound semiconductor
By using a group III-V compound semiconductor made of a group III nitride such as a system compound semiconductor, 1.9 eV to 6.2 eV can be obtained.
, High-efficiency short-wavelength light emission can be obtained over a wide range, and a desired light-emitting wavelength can be obtained by adjusting the mixed crystal ratio.

Further, in the present embodiment, in the display device, a plurality of light emitting diodes 70 made of a wurtzite compound semiconductor crystal whose light emission direction is substantially orthogonal to the c-axis direction are used. The light-emitting diode for the right eye polarized in a certain direction u and the light-emitting diode for the left eye polarized in a direction v perpendicular to the polarization direction u of the right-eye light-emitting diode were arranged so as to obtain a stereoscopic display. It is characterized by the following.

Light emitting diode 70 made of wurtzite compound semiconductor crystal whose light emission direction is substantially orthogonal to the c-axis direction
Is perpendicular to the c-axis direction, that is, polarized in the a-axis direction. When the light-emitting diode 70 polarized in the a-axis direction is rotated by 90 ° about the light emission direction as an axis, the c-axis direction Since the light is linearly polarized light that is perpendicular to the polarization direction and perpendicular to the polarization direction before rotation, a stereoscopic image can be displayed by using one for the right eye and the other for the left eye.

In FIG. 19, 69a and 69b
Indicates a pair of terminals connected to the light emitting diode 70. First Example Here, a first example of the present embodiment will be described with reference to FIGS. 20 (a) and (b) and FIGS. 21 (a) and (b). FIG. 20A is a cross-sectional view of a light-emitting diode, and FIG. 20B is a cross-sectional view of a case where the light-emitting diode is formed into an element. FIG. 21 (a)
FIG. 21 is a band diagram near the GaN point of the GaN-based compound semiconductor, and FIG. 21B is a diagram showing a polarization angle distribution of the emission intensity.

First, as shown in FIG.
The GaN buffer layer 72 having a thickness of 5 to 50 nm, for example, 20 nm, is formed on the sapphire substrate 71 having the 1) plane, that is, the c-plane as a main surface, by MOVPE (metal organic chemical vapor deposition). .5 to 5.0 μm, for example, 3.0 μm n-type Al
_0.05 Ga _0.95 N layer 73, thickness 10 to 100 nm, for example, 50
nm In _0.1 Ga _0.9 N active layer 74 and a thickness of 0.1 to 1.
0 μm, for example, 0.5 μm p-type Al _0.05 Ga _0.95 N layer 75
Are sequentially epitaxially grown.

Next, after etching by a reactive ion etching method so that a part of the n-type Al _0.05 Ga _0.95 N layer 73 is exposed, a Ni electrode is formed on the surface of the p-type Al _0.05 Ga _0.95 N layer 75 as a p-side electrode. 76 and n-type Al
_On the exposed surface of the _0.05 Ga _0.95 N layer 73, a Ti electrode 77 is provided as an n-side electrode. In this case, each layer of the GaN buffer layer 72 to the p-type Al _0.05 Ga _0.95 N layer 75, since the growth in the c-axis direction of the sapphire substrate 71, the c axis is the main surface perpendicular of the sapphire substrate 17 . The c-axis direction is <0
001> direction.

The light emitting diode 78 formed as described above is mounted on the stem 79 so that the light emission direction is substantially perpendicular to the c-axis direction, as shown in FIG. In this case, the stem 79 is mounted via an insulator spacer 80 to prevent a short circuit, and the Ti electrode 77 as the n-side electrode is connected to the minus terminal 81.
Then, a Ni electrode 76 as a p-side electrode is wire-bonded to the plus terminal 82, and finally, resin molding is performed with an epoxy resin or the like.

FIG. 21 (a) is a band diagram near the GaN point of the GaN-based compound semiconductor. As is clear from the figure, the lowest energy band, ie, HH ( Heavy Hole) and LH (Ligh
t Hole) degenerates doubly, and is separated in energy by the spin-orbit interaction.
A band called CH peculiar to the GaN-based compound semiconductor appears.

In such a GaN-based compound semiconductor, light emission occurs due to the transition between the point Γ, ie, the conduction band at Kz = 0, and the HH band and LH band. And the LH band are bands in the a-axis direction, so that light polarized in a direction perpendicular to the c-axis can be obtained. FIG. 21B is a diagram showing a polarization angle distribution of the light emission intensity of the light emitting diode according to the present embodiment of the present invention viewed from the light emission direction, and the light polarized parallel to the a-axis, that is, polarized in the a-axis direction. However, light polarized at 90 ° to the a-axis, that is, light polarized perpendicular to the a-axis is hardly obtained.

Therefore, in the present invention, linearly polarized light polarized in a specific direction can be obtained without using a polarizer or the like, so that the number of components is not increased, and a combination of a light emitting diode and a polarizer is used. Since no process is required, the production cost can be reduced.
In the first example, (000)
1) A sapphire substrate whose main surface is used is
The sapphire substrate is not limited to a sapphire substrate having a (0001) plane as a main surface, but is a sapphire substrate having a (11-20) plane as a main surface.
Alternatively, a spinel substrate having a (111) plane as a main surface may be used.

[0155]Second example Next, a second example of the present invention will be described with reference to FIG.
First, as shown in FIG.
MOV is placed on a sapphire substrate 91 whose principal surface is
Using the PE method, GaN having a thickness of 5 to 50 nm, for example, 20 nm
The buffer layer 92 has a thickness of 0.5 to 5.0 μm, for example, 3.0.
0 μm n-type Al _0.05Ga_0.95N layer 93, thickness 10 to 100
nm, for example 50 nm ln_0.1Ga_0.9N active layer 94 and thickness
0.1-1.0 μm, for example, 0.5 μm p-type Al
_0.05Ga_0.95The N layer 95 is sequentially grown epitaxially.

Next, after exposing a part of the n-type Al _0.05 Ga _0.95 N layer 93 by a reactive ion etching method,
On the surface of the p-type Al _0.05 Ga _0.95 N layer 95, a translucent electrode 96 made of very thin Ni is provided as a p-side electrode, and
Type Al _0.05 Ga _0.95 N
An electrode 97 is provided. In this case, the GaN buffer layer 9
Since the direction of the c-axis of each layer of the p-type Al _0.05 Ga _0.95 N layer 95 from 2 grows in the direction within the substrate surface of the sapphire substrate 91, the c-axis becomes parallel to the substrate surface.

As shown in FIG. 22B, the light emitting diode 84 thus formed is connected to the stem 85 using a conductive paste so that the light emission direction is substantially perpendicular to the c-axis direction. Mount. And an n-side electrode
The Ti electrode 97 is wire-bonded to the minus terminal 86, and the translucent electrode 96, which is the p-side electrode, is wire-bonded to the plus terminal 87, and finally sealed with a mold resin 88 such as epoxy resin.

Also in this case, as in the first example, since the light emission direction is perpendicular to the c-axis, light polarized in the a-axis direction is obtained, and the light is polarized by 90 ° with respect to the a-axis. That is, light polarized perpendicular to the a-axis is hardly obtained. Therefore, in the present invention, since linearly polarized light polarized in a specific direction can be obtained without using a polarizer or the like, the number of components is not increased, and a step of combining a light emitting diode and a polarizer is unnecessary. become. As a result, the production cost of the light emitting diode is reduced.

Further, in the case of the second example, since the light emitting device is of the surface emitting type, the light emitting area can be made larger than that of the first example, and the emission intensity is about 10 times that of the first example. Can be expected. In the second example, a sapphire substrate having an r-plane as a main surface is used as the substrate. However, the substrate is not limited to a sapphire substrate having an r-plane as a main surface.
SiC substrate having the (100) plane as a main surface, or (11-
20) A SiC substrate having a plane as a main surface may be used.

In the second example, the translucent electrode 96 made of a thin Ni film is used as the p-side electrode. However, the translucent electrode 96 is not limited to the translucent electrode 96. The light may be extracted from between the meshes. Third Example Next, a third example of the present invention will be described with reference to FIG.

FIG. 23 shows a display panel 90 for displaying a stereoscopic image using the light emitting diodes of the first and second examples. For example, using the light emitting diode of the first example, a light emitting diode 98 arranged so that its polarization direction becomes the X direction, and a Y light arranged such that its deflection direction is rotated by 90 ° about the optical axis of this light emitting diode 98. It is configured by combining a light emitting diode 99 that is polarized in the direction. The X direction and the Y direction are both parallel to the surface of the display panel 90, and the X direction and the Y direction are orthogonal to each other.

In this case, one light emitting diode 98 is used for the right eye, the other light emitting diode 99 is used for the left eye, and different image signals are input to both, and the light emitting display images are mutually used for the right eye and the left eye. Viewing through different polarizers will display a stereoscopic image. Note that in this case, an angle that is purely parallel to the a-axis direction is ±
Light having a polarization angle in the range of about 20 ° can be effectively used.

Since the display device of the third example is a luminous display, the brightness can be made higher than that of a conventional projection type stereoscopic display device, and therefore, it can be used in a bright place even if it is enlarged. become. In this case, for example, 100
When configuring the display panel 90 of inch, approximately 200
It will consist of 10,000 pixels. The arrangement of the light emitting diodes 98 polarized in the X direction and the light emitting diodes 99 polarized in the Y direction may be alternately arranged one by one as shown in FIG. A plurality of light emitting diodes may be arranged alternately in each case. Further, by adjusting the light emission wavelength of each light emitting diode, color display is also possible.

The plane orientation in the above embodiment is an example, and includes all planes which are crystallographically equivalent to the stated plane orientation. In each of the above examples, ln _0.1 Ga _0.9 N having an ln composition ratio of _0.1 is used for the active layer, but the mixed crystal ratio is changed to Al _x In _y according to a required wavelength.
Ga _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) may be changed, and accordingly, the p-type
Al _0.05 Ga _0.95 N layer and n-type Al _0.05 Ga _0.95 large AI forbidden band width than the N layer of the active layer _{a ln b Ga 1-ab N} (0 ≦ a ≦ 1,
0 ≦ b ≦ 1).

When a sapphire substrate is used instead of a GaN substrate, the main surface of the substrate is set to be a (11-20) plane. As described above, according to the present embodiment, GaN
When a light emitting diode is formed using a wurtzite compound semiconductor such as a wurtzite compound semiconductor, the light is emitted in a direction perpendicular to the c-axis of the wurtzite compound semiconductor. You can get
In addition, by using such linearly polarized light emitting diodes, a stereoscopic image display device using light emitting display that can be used even in a bright place can be configured.

[0166]

As described above, according to the present invention, by selecting the main surface of the crystal substrate, the c-axis of the hexagonal or wurtzite type semiconductor layer formed on the crystal substrate can be adjusted. In order to prevent the active layer from being perpendicular to the plane of the semiconductor layer, a compressive strain or a tensile strain in the plane direction is applied to the active layer of the hexagonal or wurtzite type formed on the crystal substrate to apply 3% to the active layer. The active layer can have axial anisotropy, so that degeneracy in the valence band of the active layer can be resolved, and the threshold current of oscillation of a semiconductor laser having such an active layer can be reduced.

According to such a structure, the plane of polarization of light emission by the compound semiconductor layer can be uniquely determined.
When a surface emitting semiconductor laser is formed by growing a barrier layer, an active layer, and the like on such a crystal substrate, the in-plane anisotropy of the active layer becomes large, and the electric field vector is determined in one direction. Can decide. Further, when the polarization plane of the oscillation light of the surface emitting semiconductor laser is uniquely determined, it can be used as a light source of a magneto-optical disk drive, and the light receiving element can be easily manufactured on the same substrate as the surface emitting semiconductor laser. become. This eliminates the need for the work of mounting the semiconductor laser and the light receiving element, which has been conventionally performed, and further promotes downsizing of the light receiving and emitting device.

On the other hand, when the c-axis direction of the wurtzite compound semiconductor crystal constituting the light emitting diode is set to be substantially orthogonal to the light emission direction, the polarization direction is determined. A plurality of pixels are arranged on the surface, and one or more light-emitting diodes constitute a part or all of the pixels, and the polarization directions of adjacent light-emitting diodes are different from each other by 90 degrees. And a light emitting diode for left-eye polarization can be adjacent to each other, and the number of components can be reduced by omitting a deflector in a three-dimensional display device, thereby reducing manufacturing costs.
Moreover, such a display device has a bright image.

[Brief description of the drawings]

FIG. 1A is a diagram showing a layer structure of a cladding layer and an active layer according to a first embodiment of the present invention, and FIG. 1B is a diagram showing an active layer obtained by the layer structure of FIG. 1A. Valence band energy band structure diagram, FIG. 1 (c) is a diagram showing the plane orientation of the main surface of the substrate used in the first embodiment of the present invention.

FIG. 2A is a layer structure diagram of a first example of a semiconductor laser adopting the layer structure of the first embodiment of the present invention as viewed from an optical output end, and FIG. Valence band energy band structure diagram of the active layer obtained by the layer structure of 2 (a), FIG. 2 (c)
FIG. 4 is a relative energy band structure diagram of two cladding layers and an active layer.

FIG. 3 is a structural diagram in the case where a substrate of a semiconductor laser employing the layer structure of the first embodiment of the present invention is formed from a high-resistance material.

FIG. 4A is a layer structure diagram of a second example of a semiconductor laser employing the layer structure of the first embodiment of the present invention as viewed from an optical output end, and FIG. FIG. 4 is a valence band energy band structure diagram of an active layer obtained by the layer structure of FIG.

FIG. 5A is a perspective view of a third example of the semiconductor laser adopting the layer structure of the first embodiment of the present invention, and FIG.
FIG. 6 is a diagram showing an inclination angle of a small surface with respect to the main surface of the substrate in the semiconductor laser of FIG.

FIG. 6A is a layer structure diagram of a fourth example of a semiconductor laser adopting the layer structure of the first embodiment of the present invention as viewed from an optical output end, and FIG. FIG. 14 is a layer structure diagram of a semiconductor laser in a case where a substrate is made of a high-resistance material in a fourth example, viewed from an optical output end.

FIG. 7 is a diagram illustrating a complete surface of each crystal when a hexagonal semiconductor layer is formed on a main surface of a tetragonal substrate having a c-axis parallel to the main surface in the first embodiment of the present invention. It is a figure which shows the relative relationship of the special form of an image.

FIG. 8 is a diagram showing an X-ray diffraction rocking curve of a hexagonal layer formed on a tetragonal substrate in the first embodiment of the present invention.

FIG. 9 shows hexagonal Al _x on a tetragonal LiAlO ₂ substrate.
FIG. 4 is an xy coordinate diagram showing a relationship between a composition ratio x and a composition ratio y when growing a Ga _1-xy In _y N layer.

FIG. 10 is a perspective view showing a layer structure excluding an electrode of a surface emitting laser according to a second embodiment of the present invention.

FIG. 11 is a perspective view showing a special form of a perfect image of a crystal of an active layer of a surface emitting laser according to a second embodiment of the present invention.

FIG. 12 is an energy band structure diagram of an active layer of a surface emitting laser according to a second embodiment of the present invention;

FIG. 13 is a graph showing the relationship between the wavelength and the PL emission intensity when the angle between the azimuth of the polarization plane of the active layer and the c-axis is a parameter in the surface emitting laser according to the second embodiment of the present invention. FIG.

FIGS. 14 (a) to (e) are diagrams showing the crystal strain dependence of the energy band of GaN constituting the active layer in the surface emitting laser according to the second embodiment of the present invention.

FIG. 15 is an experiment on the relationship between the wavelength and the PL emission intensity when the angle between the azimuth of the polarization plane of the active layer and the c-axis is a parameter in the surface emitting laser according to the second embodiment of the present invention. FIG.

FIG. 16 is a graph showing the relationship between the orientation of the polarization plane of the active layer, the angle formed by the c-axis, and the PL emission intensity in the surface emitting laser according to the second embodiment of the present invention by calculation and experiment. FIG.

FIG. 17 is a sectional view showing a surface emitting laser according to a second embodiment of the present invention.

FIG. 18A is a sectional view showing an optical device having a surface emitting laser and a light receiving element according to a second embodiment of the present invention, and FIG.
FIG. 8 (b) is a plan view of the optical device.

FIG. 19 (a) is a diagram showing the principle configuration of an edge-emitting light emitting diode according to a third embodiment of the present invention, and FIG. 19 (b).
FIG. 4 is a diagram showing the basic configuration of a surface-emitting light emitting diode according to a third embodiment of the present invention.

FIG. 20 (a) is a layer structure diagram of an edge-emitting light-emitting diode according to a third embodiment of the present invention, and FIG. 20 (b) is a cross-sectional view showing a configuration in which the light-emitting diode is packaged. It is.

21 (a) is a band diagram of a GaN-based compound semiconductor in the light emitting diode shown in FIG. 20 (a), and FIG. 21 (b) is a graph showing the emission intensity of the light emitting diode viewed from the light emission direction. It is a figure which shows a polarization angle distribution.

FIG. 22A is a layer structure diagram of a surface-emitting light emitting diode according to a third embodiment of the present invention, and FIG. 22B is a cross-sectional view showing a configuration in which the light emitting diode is packaged. is there.

FIG. 23 is a plan view showing a deflection relationship of light emitting diodes used in a display device according to a third embodiment of the present invention.

FIG. 24A is a sectional view showing a first example of a conventional semiconductor diode, and FIG. 24B is a sectional view showing a second example of a conventional semiconductor diode.

FIGS. 25 (a) and 25 (b) are energy band diagrams of a valence band of a conventional semiconductor diode.

FIG. 26 is a perspective view showing a conventional surface-emitting type semiconductor laser.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 first semiconductor 2 second semiconductor 3 third semiconductor 1 l n-type GaN (1-100) substrate 12 n-type Al _0.1 Ga _0.9 N cladding layer 13 n-type GaN optical guide layer 14 Ga _0.9 In _0.1 N activity Layer 15 p-type GaN optical guide layer 16 p-type Al _0.1 Ga _0.9 N cladding layer 17 Ti / Au electrode 18 Ni / Au electrode 21 n-type GaN (1-100) substrate 22 n-type Al _0.4 Ga _0.3 In _0.3 N cladding layer 23 n-type Al _0.15 Ga _0.65 In _0.2 N optical guide layer 24 Ga _0.9 In _0.1 N active layer 25 p-type Al _0.15 Ga _0.65 In _0.2 N optical guide layer 26 p-type Al _0.4 Ga _0.3 In _0.3 N cladding layer 27 Ti / Au Electrode 28 Ni / Au electrode 31 n-type GaN (0001) substrate 32 (11-21) small surface 33 insulating film 34 (1-100) cleavage surface 41 substrate 42 active layer 43 DBR mirror 44 c axis 44 az polarized light 45 x polarized light 46 y-polarized light 47, 48 barrier layer 49, 51 contact layer 50a, 50 Electrode 52 Buffer layer 53 SiC substrate 54 AlN High temperature buffer layer 55 Mirror layer 56 N-type barrier layer 57 Lower light confinement layer 58 Active layer 59 P-type barrier layer 60 Upper light confinement layer 61 Groove 62 Column 62 Column 63 63 Flange 64 Light emission window 65 n-side electrode 66 surface emitting semiconductor laser (light emitting element) 67 photodiode (light receiving element) 68 power supply 69 light quantity detection circuit 70 light emitting diode 71 sapphire substrate 72 GaN buffer layer 73 n-type Al _0.05 Ga _0.95 N layer 74 Al _0.1 Ga _0.9 N Active layer 75 p-type Al _0.05 Ga _0.95 N layer 76 Ni electrode 77 Ti electrode 78 Light emitting diode 79 Stem 80 Insulator spacer 81 Negative terminal 82 Plus terminal 83 Mold resin 84 Light emitting diode 85 Stem 86 Negative terminal 87 Plus terminal 88 Mold resin 90 Display panel 91 Safari IA substrate 92 GaN buffer layer 93 n-type Alo.o 5Gao.9 5N layer 94 Al _0.1 Ga _0.9 N active layer 95 p-type Al _0.05 Ga _0.95 N layer 96 light-emitting diodes 99 to polarize the semitransparent electrode 97 Ti electrode 98 horizontally Vertically polarized light emitting diode

Claims (30)

[Claims] A second semiconductor layer formed directly or via a first semiconductor layer on a main surface of a substrate; and an energy band gap formed on the second semiconductor layer and having an energy band gap of the second semiconductor layer. An active layer made of a semiconductor smaller than the second semiconductor layer and having uniaxial anisotropy; a third semiconductor layer formed on the active layer and having an energy band gap larger than the active layer; A semiconductor layer, a pair of electrodes for flowing current in a thickness direction of the active layer and the third semiconductor layer, and at least a thickness direction of the active layer is different from the axis of the uniaxial anisotropy. A semiconductor light emitting device characterized by being in a direction. 2. The semiconductor light emitting device according to claim 1, wherein said semiconductor constituting said active layer is a wurtzite nitride semiconductor. 3. The wurtzite-type nitride is Al _x Ga _1-xy In _y
N, the composition ratio x is 0 ≦ x ≦ 1, and the composition ratio y is 0 ≦
y ≦ 1 and the composition ratio x and the composition ratio y are xy coordinates in the xy coordinates.
214x−0.328 straight line and y = 0.353x−
3. The semiconductor optical device according to claim 2, wherein the semiconductor optical device exists in a range between the straight lines indicating 0.209. 4. The substrate is made of any one of GaN, AlN, and SiC, and the main surface is a {11-20} plane or a {1}.
-100 plane, or {11-20} plane or {1-
2. The semiconductor optical device according to claim 1, wherein the surface is inclined within a range of -5 degrees to +5 degrees from a 100-degree plane. 5. The substrate according to claim 1, wherein the substrate is a LiAlO ₂ substrate, and the main surface is a {100} plane or a plane turned off at an angle of −5 to +5 degrees from the {100} plane. 13. The semiconductor optical device according to claim 1. 6. The active layer has a uniaxial anisotropic crystal structure, and has a strain anisotropy in a c plane when a strain is applied in a plane not perpendicular to the c axis showing the anisotropy. The semiconductor light emitting device according to claim 1, wherein: 7. The semiconductor light emitting device according to claim 6, wherein said active layer is made of AI _x Ga _{1-xy In y} N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1). . 8. The semiconductor device according to claim 8, wherein said second semiconductor is Al _u Ga _1-uv ln _v N
(Where, 0 ≦ u ≦ 1, 0 ≦ v ≦ 1) consists, and said third semiconductor is _{Al w Ga 1-wz 1n z} N ( where, 0 ≦ w ≦
7. The semiconductor light emitting device according to claim 6, wherein 1, 0≤z≤1). 9. The a-axis lattice constant a ₁ of the active layer and the a-axis lattice constant a of the second semiconductor layer and the third semiconductor layer.
_2, a ₃ and _{is, a 1 <a 2, a} 1 < a semiconductor light-emitting device according to claim 6, characterized in that to satisfy the relation of a _3. 10. The c-axis lattice constant c ₁ of the active layer and the c-axis lattice constants c ₂ and c _{3 of} the second semiconductor layer and the third semiconductor layer are c ₁ <c ₂ , 7. The semiconductor light emitting device according to claim 6, wherein a relationship of c ₁ <c ₃ is satisfied. And 11. the lattice constant a ₁ of a-axis of the active layer, the lattice constant of a-axis of the second semiconductor layer and the third semiconductor layer, and a _2, a _3, a _1> a ₂ 7. The semiconductor light emitting device according to claim 6, wherein a relationship of a ₁ > a ₃ is satisfied. 12. The c-axis lattice constant c ₁ of the active layer and the c-axis lattice constants c ₂ and c _{3 of} the second semiconductor layer and the third semiconductor layer are c ₁ > c ₂ , the device according to claim 6, characterized in that to satisfy the relation of c _1> c _3. 13. The method according to claim 13, wherein the main surface of the substrate is {1-100}.
Off angle θ with respect to either plane or {11-20} plane
7. The semiconductor light emitting device according to claim 6, wherein the substrate is turned off by 0 ° ≦ θ ≦ 10 °. 14. The substrate, the second and third semiconductor layers, and the active layer have a {0001} plane, {1-100}
7. The semiconductor light emitting device according to claim 6, wherein the semiconductor light emitting device is cleaved at any one of a plane and a {11-20} plane. 15. The semiconductor device according to claim 15, wherein the main surface of the substrate is a small surface having a plane orientation that intersects a {0001} plane, and the active layer formed above the small surface is a light emitting portion. A semiconductor light emitting device according to claim 6. 16. The facet may be a {1-100} face or a {1} face.
The {1-100} plane or the {11-2} is formed in a plane orientation perpendicular to either the {1-20} plane or the {0001} plane.
16. The semiconductor light emitting device according to claim 15, wherein the {0} plane or the {0001} plane is a cleavage plane at both ends of the resonator. 17. A mirror layer is formed below the second semiconductor layer or above the third semiconductor layer, and the active layer, the second and third semiconductor layers having the mirror layer as one end. 2. The semiconductor light emitting device according to claim 1, wherein a resonator is formed in a thickness direction of the semiconductor light emitting device. 18. The semiconductor light emitting device according to claim 17, wherein a resonance wavelength of said resonator is a wavelength at which photoluminescence light intensity is maximized. 19. The multi-quantum well layer having a multi-layer structure of a first layer of GaN or lnGaN and a second layer of AlGalnN or GaN or InGaN, a single layer of GaN, a single layer of lnGaN or AlG.
18. The optical semiconductor device according to claim 17, comprising one of alnN single layers. 20. The method according to claim 20, wherein the main surface of the substrate is a (1) of a SiC substrate.
18. The semiconductor light emitting device according to claim 17, wherein the semiconductor light emitting device is any one of a (1-20) plane, a (1-100) plane, and a (1-102) plane of a sapphire substrate. 21. A first barrier layer of AIGaN of a first conductivity type grown on a SiC substrate having a (11-20) plane as a main surface, and a first barrier layer deposited on the first barrier layer. GaN layer or lnGaN
An active layer composed of a multiple quantum well layer, a GaN layer or an lnGaN layer including a layer; a second barrier layer composed of AIGaN of the second conductivity type deposited on the active layer; A reflecting mirror comprising a multilayer film provided as a first reflecting surface, an optical resonator in a film thickness direction having a second reflecting surface below the first barrier layer, and a first and a second electrode. A semiconductor light emitting device comprising: 22. A substrate having a c-axis parallel to the main surface, a first active layer formed above the substrate and made of wurtzite structure crystal, and formed below the first active layer. First
A first barrier layer containing a conductivity type impurity, a second barrier layer containing a second conductivity type impurity formed on the first active layer, the first active layer and first and second A surface-emitting semiconductor laser having an electrode for flowing a current in the thickness direction of the barrier layer; and a wurtzite-structured crystal formed above the substrate and electrically separated from the surface-emitting semiconductor laser. 2 active layer, a first semiconductor layer containing a first conductivity type impurity formed below the second active layer, and a second conductivity type impurity formed on the second active layer. A second semiconductor layer including:
An optical semiconductor device comprising: a light receiving element having the second active layer and an electrode for extracting a current flowing in the thickness direction of the first and second semiconductor layers to the outside. 23. The first active layer of the semiconductor laser and the second active layer of the light receiving element are composed of GaN, InGaN, Al
23. The method according to claim 22, wherein the material is made of GaN or AlGaInN.
The optical semiconductor device according to the above. 24. The semiconductor laser according to claim 17, wherein said first and second barrier layers of said semiconductor laser and said first and second semiconductor layers of said light receiving element are made of GaN, InGaN, AlGaN or AlGaInN. 23. The optical semiconductor device according to 22. 25. The optical semiconductor device according to claim 22, wherein said substrate is made of one of silicon carbide and sapphire. 26. The optical semiconductor device according to claim 22, wherein said substrate has a hexagonal structure, and said main surface is a {1-100} plane or a {11-20} plane. 27. A light-emitting diode, wherein the c-axis direction of the wurtzite compound semiconductor crystal is substantially orthogonal to the light emission direction. 28. The light emitting diode according to claim 27, wherein a c-axis direction of said wurtzite compound semiconductor crystal and a crystal growth direction are substantially perpendicular to each other. 29. The wurtzite-type compound semiconductor crystal according to claim 29, wherein
28. The light emitting diode according to claim 27, wherein the light emitting diode is a group III-V compound semiconductor made of a group I nitride. 30. A plurality of light emitting diodes made of a wurtzite compound semiconductor crystal whose light emission direction is substantially orthogonal to the c-axis direction, and the right eye polarized in a certain polarization direction among the plurality of light emitting diodes. A display device comprising a light-emitting diode and a left-eye light-emitting diode polarized in a direction perpendicular to the polarization direction of the right-eye light-emitting diode to obtain a three-dimensional display.