JPH09232629A - Semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the spread of the high density dislocation generated on the interface between a substrate and a growth layer to growth direction by a method wherein a cubic crystal distortion layer, having a substantial growth surface 111}, is provided between the growth substrate of a semiconductor element having an element part consisting of a hexagonal crystal semiconductor. SOLUTION: A cubic crystal type n-GaN layer 11, having a growth surface, is formed on a sapphire substrate 10, and a distorted superlattice layer 12, on which an n-GaN layer and an n-HlGaN layer are alternately frown in critical film thickness or less, if formed thereon. An n-GaN layer 13, a clad layer 14, an active layer 15, a clad layer 16 and a contact layer 17 are successively grown thereon. Most of the dislocation of the high density generated by the lattice dismatching on the interface between the n-GaN layer 11 and the sapphire substrate 10 is changed its propagation direction by the distorted superlattice layer 12, and the propagation to the growth direction of transposition of high density generated on the interface between the substrate and the growth layer can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device made of a compound semiconductor containing nitrogen such as GaN, AlGaN and InGaN.

[0002]

2. Description of the Related Art In recent years, a semiconductor laser (LD) capable of emitting light at a short wavelength has been required in order to improve the recording density of an optical disk and the resolution of a laser printer. As a short wavelength semiconductor laser made of InGaAlP material 6
The 00 nm band light source has already been put to practical use, with its characteristics improved to a level where both reading and writing of a disc are possible. Blue semiconductor lasers are being actively developed to further improve the recording density.

In such development, a blue-green semiconductor laser using a ZnSe-based material, which is a II-VI group compound semiconductor, has been developed for practical use such as a long life and improved reliability since the oscillation operation was confirmed. Is being actively conducted.

However, in this material system, reliability is obtained because dislocations caused by a lattice mismatch difference and a thermal expansion coefficient difference between the growth substrate and the growth layer having the element portion are multiplied by energization. It is becoming clear that there are high barriers to practical use, such as the lack of a product and its short life.

On the other hand, GaN-based semiconductor lasers have a material Z
It is expected to be a promising material because it can make the wavelength shorter than that of the nSe system and is harder in material than the ZnSe system in terms of reliability. This material system is 10 ⁸ ~
Although there is a dislocation of 10 ¹⁰ cm ^-2 , the reliability of the LED has been confirmed for more than 10,000 hours, and the research and development of the blue semiconductor laser satisfying the conditions necessary for the next-generation optical disc system light source is now active. Has been done in.

As described above, with LEDs, 10 ⁸ to 10 ¹⁰ cm
The existence of the ^-2 dislocation is not a big problem. But,
In the LD requiring high current density injection, the above 10 ⁸ to 1
The presence of dislocations with a high density of 0 ¹⁰ cm ^-2 causes a decrease in reliability.

By the way, a GaN-based semiconductor element which is generally used as an LED or LD at present is formed on a sapphire substrate and is made of a hexagonal (wurtzite) type semiconductor. GaN-based crystals exist in hexagonal type and cubic type, but so far G for obtaining LEDs and LDs is used.
As an aN crystal, it has been reported that the hexagonal type is more advantageous in terms of crystal quality.

FIG. 9 is a sectional view showing a schematic structure of a conventional GaN-based semiconductor device. Hexagonal dislocations in crystals (101 - ^0), (11 - 00) (1 ^-. Represents hereinafter the same one of the inverse) for prone most slip on cylindrical surface such as shown in FIG. 9 Sapphire substrate and GaN
10 ⁸ to 10 ¹⁰ cm ^-2 caused by lattice mismatch between layers
Of high density propagates in the growth direction (perpendicular to the growth surface) and penetrates to the surface of the active layer.

Therefore, the active layer has 10 ⁸ to 10 ¹⁰ cm.
^{-2 has} a high density of dislocations, so the crystallinity is poor, and in the case of LDs, a large current density injection causes propagation and multiplication of dislocations, which lowers the reliability of the device, causing a problem.

In order to secure the reliability of the GaN-based semiconductor laser, the density of dislocations generated at the interface between the substrate and the growth layer should be reduced, or the existing 10 ⁸ to 10 ¹⁰ cm ^-2.
It is important not to propagate high density dislocations in the active layer.

[0011]

As described above, in the hexagonal type semiconductor device such as the conventional nitride semiconductor device, dislocations generated at the interface between the substrate and the growth layer are in the growth direction (growth plane). Since it is most likely to propagate in the vertical direction), dislocations once generated at the interface penetrate the element portion as they are and penetrate to the surface of the growth layer. Particularly, in the case of a GaN-based LD, there is a problem that high-density dislocations of 10 ⁸ to 10 ¹⁰ cm ⁻² propagate to the active layer, which is the heart of the device, and the injection of a large current density deteriorates the device reliability.

The present invention has been made in consideration of the above circumstances, and has a structure in which dislocations generated at the interface between the substrate and the growth layer do not penetrate into the element heart (the active layer in the case of a light emitting element). Accordingly, it is an object of the present invention to provide a semiconductor device capable of ensuring the reliability of the device.

[0013]

In order to solve the above-mentioned problems, first of all, the invention corresponding to claim 1 is a semiconductor device having an element part made of a hexagonal type semiconductor, which comprises a growth substrate and an element part. It is a semiconductor device in which a cubic strain layer having a substantial {111} growth plane is provided therebetween.

Next, an invention according to claim 2 is a semiconductor device having a device portion made of a hexagonal type semiconductor, wherein a {111} plane is provided between the growth substrate and the device portion by 30.
Substantial {111} including a growth surface with a tilt within degrees
A semiconductor device provided with a cubic strained superlattice having a growth surface. (Operation) Accordingly, according to the semiconductor device of the invention corresponding to claim 1, first, the cubic strained layer having the {111} growth plane is provided below the heart of the hexagonal semiconductor device. It is possible to suppress the propagation of high-density dislocations generated at the interface between the substrate and the growth layer in the growth direction.

That is, when the dislocations from the substrate reach the strained layer, most of the dislocations escape to the side of the semiconductor element due to the slip on the {111} plane which is the slip plane of the cubic crystal. .

Therefore, by having a structure in which dislocations generated at the interface between the substrate and the growth layer do not penetrate into the element heart (the active layer in the case of a light emitting element), the reliability of the element can be secured.

The strained layer may be a single strained layer, but it is more effective if a strained superlattice layer is used, for example. Next, in the semiconductor element of the invention according to claim 2, the substantial {111} growth plane has an inclination within 30 degrees from the {111} plane such as the {112} growth plane or the {113} growth plane. Is included in the growth surface. Even if there is an inclination of about 30 degrees or less from the {111} plane, the above-mentioned dislocation effect due to slippage on the {111} plane works sufficiently, and operates similarly to the semiconductor element according to claim 1.

As means for solving the above-mentioned problems, the following contents are included in addition to the above means. (1) The semiconductor element according to claim 1 or 2, wherein the element portion is made of a compound semiconductor containing nitrogen such as GaN, AlGaN, or InGaN. (2) In a semiconductor device having a device portion made of a hexagonal semiconductor, a cubic semiconductor layer having a substantial {111} growth plane is provided between a growth substrate and the device portion,
The cubic semiconductor layer is a layer softer than other semiconductor layers in contact with the element section side. (3) In a semiconductor device having a device portion made of a hexagonal semiconductor, a cubic semiconductor layer having a substantial {111} growth plane is provided between a growth substrate and the device portion,
The cubic crystal semiconductor layer is a harder layer than other semiconductor layers in contact with the growth substrate side.

Although a sufficient dislocation effect can be obtained even when a single layer is used as the cubic semiconductor layer as in the above (2) or (3), each cubic in (2) and (3) Dislocations can be reduced most effectively in the case of a strained superlattice using a combination of crystalline semiconductor layers.

[0020]

Embodiments of the present invention will be described below in detail with reference to the drawings. (First Embodiment of the Invention) FIG. 1 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device to which a semiconductor element according to the first embodiment of the present invention is applied.

In this semiconductor laser device, it is formed on the sapphire substrate 10. Sapphire substrate 10
On top, by metalorganic vapor phase epitaxy (MOCVD),
First, cubic type (sphalerite type) with (111) growth plane
N-GaN layer 11 (Si-doped, 3-5 × 10 ¹⁸ c
m ^-3 ) is grown at 650 ° C.

A strained superlattice layer 12 (Si) having n-GaN layers and n-AlGaN layers alternately grown thereon with a critical film thickness or less is formed thereon.
Dope, 3-5 × 10 ¹⁸ cm ⁻³ ) is grown at 650 ° C.
The strained superlattice layer 12 is grown on the zinc blende type n-GaN layer 11 having a (111) growth surface under the same conditions, so that a strained zinc blende type strained superlattice layer having a similar (111) growth surface is obtained. It becomes a lattice layer.

Next, n having a hexagonal type (wurtzite type) is formed on the strained superlattice layer 12 by adjusting the growth conditions.
Forming a GaN layer 13 (Si-doped, 3-5 × 10 ¹⁸ cm ⁻³ ), and subsequently forming a wurtzite type n-Al _0.5 Ga _0.5.
N cladding layer 14 (Si-doped, 5 × 10 ¹⁷ cm ⁻³ , layer thickness 0.15 μm), GaN active layer 15 (undoped, layer thickness 0.1 μm), p-Al _0.5 Ga _0.5 N cladding layer 16
(Mg-doped, 5 × 10 ¹⁷ cm ⁻³ , layer thickness 0.15 μm),
GaN contact layer 17 (Mg-doped, 1-3 × 10 ¹⁸
cm ⁻³ , layer thickness 0.1 μm) are successively grown at 1150 ° C. Here, the control of the crystal form from the zinc blende type crystal to the wurtzite type crystal is performed by controlling the growth temperature and the flow rate ratio of hydrogen, nitrogen carrier gas, and ammonia as a nitrogen source.

Although not particularly shown, the n-GaN layer 1
1 and the sapphire substrate 10 are provided with an AlN buffer layer grown at a low temperature of 550 ° C. during MOCVD growth.

Further, a p-side electrode 18 is provided on the upper surface of the GaN contact layer 17, and n on the n-GaN layer 13 is provided.
An n-side electrode 19 is provided on the upper surface portion where the -AlGaN cladding layer 14 is not stacked. Thus, the blue semiconductor laser device according to this embodiment was obtained.

When the element of the blue semiconductor laser device having the above structure was observed from the cross section with a transmission electron microscope, 10 ⁸ to 10 ¹⁰ were generated due to lattice mismatch at the interface between the sapphire substrate 10 and the n-GaN layer 11. Most of the high-density dislocations of cm ⁻² change the propagation direction in the strained superlattice layer 12 provided by the present invention, and the dislocation density in the active layer 15 is reduced to the order of 10 ³ cm ⁻³ . It was confirmed.

The reason why the dislocation density is reduced will be described with reference to FIG. FIG. 2 is a schematic diagram for explaining how dislocations are eliminated in the semiconductor device of this embodiment.

When a dislocation propagating in a semiconductor tries to enter a relatively hard semiconductor layer from a soft semiconductor layer, the dislocation propagation is blocked and the propagation direction is changed. FIG. 2 shows this state.

Compared to the n-GaN layer, the n-GaN layer and the n-AlGaN layer forming the strained superlattice layer 12 have n-Al layers.
The GaN layer is a hard layer. Therefore, as shown in the figure, the dislocation 70 changes its propagation direction in the horizontal direction at the position where the n-AlGaN layer tries to enter the n-GaN layer.

Specifically, such a change in the dislocation propagation direction occurs when the slip surface of the cubic crystal is (111).
It depends on being a face. That is, the sapphire substrate 10 and the n-GaN are provided by providing the strained superlattice layer 12 including the zinc blende type n-GaN layer and the n-AlGaN layer having the (111) growth surface between the substrate and the active layer. Most of the dislocations generated at the interface with the layer 11 are the most slippery on the (111) plane, which is the slip plane of the cubic crystal, and on the (111) plane parallel to the growth plane from the strain direction of the strained superlattice. Therefore, it is considered that the propagation direction is bent and the light exits to the side surface of the element (direction perpendicular to the growth direction).

As a result, as described above, the dislocation density of the semiconductor layer including the active layer 15 after the n-GaN layer 13 including the active layer 15 is significantly reduced. The semiconductor laser device manufactured as described above continuously oscillated at room temperature with a threshold value of 150 mA. The oscillation wavelength was 365 nm and the operating voltage was 10V.

As described above, according to the semiconductor device according to the first embodiment of the present invention, a cubic strained superlattice having a (111) growth surface in the lower portion of the core of the hexagonal semiconductor device. Layers and the like are provided to suppress the propagation of high-density dislocations generated at the interface between the substrate and the growth surface in the growth direction. Therefore, in the GaN-based blue semiconductor laser, it occurs at the interface between the substrate and the growth layer. Dislocations of 10 ⁸ to 10 ¹⁰ cm ^-2 can be reduced to 10 ³ cm ^-2 in the active layer portion by the strained superlattice, and the reliability can be significantly improved.

That is, GaN having the structure described in the prior art.
In the blue semiconductor laser, it is difficult to oscillate because of the presence of 10 ⁸ to 10 ¹⁰ cm ^-2 generated at the interface between the substrate and the growth layer. Or, the reliability of the device has not been obtained, such as the device being destroyed within the operating life of several minutes.

On the other hand, in the above-described semiconductor device manufactured according to the contents of the present embodiment, the operating life is 100 to 10 of that of the conventional semiconductor device although the operating voltage remains high.
The reliability of the device is greatly improved. (Second Embodiment of the Invention) As a second embodiment, a blue semiconductor laser device having a slightly different structure manufactured by the MOCVD method will be described as in the first embodiment.

FIG. 3 is a sectional view showing a schematic structure of a GaN-based blue semiconductor laser device to which the semiconductor element according to the second embodiment of the present invention is applied. In this GaN-based blue semiconductor laser device, a GaN buffer layer (not shown) is provided on the sapphire substrate 20 at a low temperature of 550 ° C., and then (111) growth is performed on the GaN buffer layer, as in the case of the first embodiment. Cubic type (sphalerite type) n-GaN layer 21 having a plane
(Si-doped, 3-5 × 10 ¹⁸ cm ⁻³ ) is grown at 750 ° C.

Further, on the n-GaN layer 21, a zinc blende type n-GaN / n also having a (111) growth surface.
-InGaN strained superlattice layer 22 (Si-doped, 3-5 x 1)
0 ¹⁸ cm ^-3 ) is grown at 750 ° C.

Next, n having a hexagonal type (wurtzite type)
A GaN layer 23 (Si-doped, 3 to 5 × 10 ¹⁸ cm ⁻³ ) is formed, and then an n-Al _0.5 Ga _0.5 N cladding layer 24 is formed.
(Si dove, 5 × 10 ¹⁷ cm ^-3 , layer thickness 0.3 μm), G
aN optical confinement layer 25 (undoped, layer thickness 0.2μ
m), In _0.1 Ga _0.9 N multiple quantum well active layer 26, G
aN optical confinement layer 27 (undoped, layer thickness 0.2 μm
m), p-Al _0.5 Ga _0.5 N cladding layer 28 (Mg-doped, 5 × 10 ¹⁷ cm ⁻³ , layer thickness 0.3 μm), GaN contact layer 29 (Mg-doped, 1-3 × 10 ¹⁸ cm ⁻³ , A layer thickness of 0.1 μm) is successively grown at 1150 ° C.

Further, a p-side electrode 30 is provided on the upper surface of the GaN contact layer 29, and n on the n-GaN layer 23 is provided.
An n-side electrode 31 is provided on the upper surface portion where the -AlGaN cladding layer 24 is not stacked. Thus, the blue semiconductor laser device according to this embodiment was obtained.

Also in this blue semiconductor laser device, the dislocation density of the active layer 26 was sufficiently reduced. Next, the oscillation operation of the blue semiconductor laser device having the above configuration will be described.

In the element of this structure, the threshold value is 75 mA and the threshold value is 50.
Continuous oscillation up to ℃. The oscillation wavelength was 395 nm, the operating voltage was 7 V, and stable operation was confirmed for up to 5000 hours. As described above, according to the semiconductor device according to the second embodiment of the present invention, as in the case of the first embodiment, the (111) growth plane is formed in the lower portion of the core of the hexagonal semiconductor device. Since the cubic strained superlattice layer and the like are provided, the same effect as in the case of the first embodiment can be obtained. (Third Embodiment of the Invention) As a third embodiment, a GaN semiconductor laser similar to that of the first and second embodiments is used.
A cubic (zinc blende type) III-V group compound semiconductor, which is formed on a GaAs substrate that is widely used for optical devices, electronic devices, and the like, will be described.

FIG. 4 is a sectional view showing a schematic structure of a GaN-based blue semiconductor laser device formed on a GaAs substrate to which the semiconductor element according to the third embodiment of the present invention is applied. In this GaN-based blue semiconductor laser device, a (111) growth surface is first formed on a cubic (zincblende) n-GaAs (111) substrate 40 by metal organic chemical vapor deposition (MOCVD). With cubic structure (sphalerite type)
N-GaN layer 41 (Si-doped, 3-5 × 10 ¹⁸ c
m ^-3 ) is grown at 550 ° C.

A strained superlattice layer 42 (S) in which an n-GaN layer and an n-InGaN layer are alternately grown to have a critical thickness or less is formed thereon.
i-doping, 3 to 5 × 10 ¹⁸ cm ⁻³ ) is provided. This strained superlattice layer 42 also becomes a zinc blende type having a similar (111) growth surface.

Next, at 750 ° C., the flow rates of hydrogen, nitrogen carrier gas, and ammonia are changed, and the n-GaN layer 43 having a hexagonal type (wurtzite type) (Si-doped, 3
˜5 × 10 ¹⁸ cm ⁻³ ), followed by wurtzite n−
Al _0.5 Ga _0.5 N cladding layer 44 (Si-doped, 5 ×
10 ¹⁷ cm ⁻³ , layer thickness 0.2 μm), In _0.1 Ga _0.9 N active layer 45 (undoped, layer thickness 200 Å), p-Al _0.5 Ga _0.5 N cladding layer 46 (Mg-doped, 5 × 10 ¹⁷ cm ^{− 3} , a layer thickness of 0.2 μm) and a GaN contact layer 47 (Mg-doped, 1-3 × 10 ¹⁸ cm ⁻³ , layer thickness of 0.1 μm) are sequentially grown at 750 ° C.

Here, the n-GaN layer 43, n-AlGaN
Layer 44, InGaN active layer 45, p-AlGaN layer 4
6. Each layer composed of the GaN contact layer 47, that is, the double hetero structure portion 51 as the element portion is constituted by the hexagonal crystal type which is more stable than the cubic crystal type, so that the reliability of the element characteristics is improved.

Further, in this semiconductor laser device,
A current confinement layer 48 made of SiO ₂ formed on a disk having an opening is provided on the GaN contact layer 47,
Further, a p-side electrode 49 is provided so as to be in direct contact with the GaN contact layer 27 via the opening. on the other hand,
An n-side electrode 50 is provided below the n-GaAs substrate 20.

When the element of the blue semiconductor laser device having the above-mentioned structure was observed from the cross section with a transmission electron microscope, the GaAs substrate 4 was observed as in the case of the first embodiment.
Most of the dislocations generated at the interface between 0 and the n-GaN layer 41 can be changed in the propagation direction as a result of slipping on the (111) growth surface by the strained superlattice layer 42 provided in the present embodiment, and It was confirmed that it penetrated to the side surface (direction perpendicular to the growth direction). The dislocation density in the active layer 45 is 10
It was reduced to ³ cm ^-3 .

Next, the oscillation operation of the blue semiconductor laser device having the above structure will be described. The semiconductor laser device having the double hetero structure of the present embodiment has a threshold value of 45 mA and is 8
It oscillated continuously up to 0 ° C. It was confirmed that the oscillation wavelength was 395 nm and the operation voltage was 4 V, and stable operation was performed for up to 7,000 hours.

As described above, according to the semiconductor device according to the third embodiment of the present invention, as in the case of the first embodiment, (11
1) In addition to providing a cubic strained superlattice layer or the like having a growth surface, a GaAs substrate 40 is used as a substrate, and a current can be passed in the substrate direction. Therefore, the same as in the case of the first embodiment. In addition to the effect, the present laser can improve the element resistance, that is, reduce the resistance value.

Similar to the prior art, that is, in the case where the insulating substrate is used as in the first embodiment, the resistance increases because the current is injected laterally. When a conductive substrate is used as the substrate, a current can be passed in the direction of the substrate, and the element resistance is remarkably improved.

That is, in the GaN-based blue semiconductor laser having the conventional structure, most of the high-density dislocations generated at the interface between the substrate and the growth layer propagate to the InGaN active layer 45,
In combination with the high resistance due to the injection of a large current density for laser oscillation, the operating life of the device was only a few minutes and reliability was not obtained.

However, in the case of this embodiment, the active layer 45
By lowering the dislocation density and lowering the resistance, the operating life was extended about 7,000 times that of the conventional one, and the reliability of the device was significantly improved. (Fourth Embodiment of the Invention) This embodiment shows the case where a single strained layer is used.

FIG. 5 is a sectional view showing a schematic structure of a GaN-based blue semiconductor laser device to which the semiconductor element according to the fourth embodiment of the present invention is applied. The same parts as those in FIG. The description is omitted.

This GaN-based blue semiconductor laser device has the same structure as that of the first embodiment, except that a cubic InGaN layer 71 is provided in place of the strained superlattice layer. This In
The GaN layer 71 is a softer layer than the n-GaN layer 13, whereby dislocations are eliminated as shown in FIG.
The dislocation density of the active layer 15 is low.

FIG. 6 is a schematic diagram for explaining how dislocations are eliminated in the semiconductor device of this embodiment. In the figure, the dislocations 70 propagating upward in the soft InGaN layer 71, when approaching the hard n-GaN layer 13, slip on the (111) growth surface and propagate in the propagation direction. The dislocation 70 is changed and escapes from the side of the semiconductor device.

As described above, the semiconductor device according to the fourth embodiment of the present invention has the same structure as that of the first embodiment, and has a cubic crystal structure instead of the strained superlattice layer. Since the InGaN layer 71 is provided, the dislocation density of the active layer can be reduced as in the case of the first embodiment. (Fifth Embodiment of the Invention) The present embodiment shows a case where a single strained layer is used.

FIG. 7 is a sectional view showing a schematic structure of a GaN-based blue semiconductor laser device to which a semiconductor element according to the fifth embodiment of the present invention is applied. The same parts as those in FIG. The description is omitted.

This GaN-based blue semiconductor laser device has the same structure as that of the first embodiment except that a cubic AlGaN layer 72 is provided instead of the strained superlattice layer. This Al
The GaN layer 72 is a harder layer than the n-GaN layer 11, and as a result, dislocations are eliminated and the active layer 15 has a low dislocation density, as shown in FIG.

FIG. 8 is a schematic diagram for explaining how dislocations are eliminated in the semiconductor device of this embodiment. In the figure, the dislocations 70 propagating upward in the n-GaN layer 11 which is a soft layer, when approaching the AlGaN layer 72 which is a hard layer, causes a slip on the (111) growth surface and changes its propagation direction. The dislocation 70 is changed and escapes from the side of the semiconductor device.

As described above, the semiconductor device according to the fifth embodiment of the present invention has the same structure as that of the first embodiment, and has a cubic crystal structure instead of the strained superlattice layer. Since the AlGaN layer 72 is provided, the dislocation density of the active layer can be reduced as in the case of the first embodiment.

In each of the above embodiments, a hexagonal sapphire substrate and a cubic GaAs substrate are used as the substrate, but the present invention is not limited to this, and SiC, Si, ZnO, spinel are used. The same can be applied even when a substrate made of, for example, neodymium gallate (NdGaO ₃ , NGO) is used.

Further, in the case of crystal growth as in the first, second, fourth and fifth embodiments, the (0001) plane of the sapphire substrate is generally used as the growth surface. not limited to this, for example, a sapphire substrate (011 - ²⁾ may be any of various aspects of the surface or the like.

Further, in each of the above embodiments, the superlattice layer 1
2, 22, 42, InGaN layer 71, AlGaN layer 72
Although the layer for removing dislocations such as, for example, has been described in the case of the {111} growth plane, the present invention is not limited to this case.
For example, if the surface has an inclination within about 30 degrees from the {111} plane such as the {112} plane or the {113} plane, the dislocation escape effect due to the slip on the (111) plane, which is the slip plane of the cubic crystal, Can be sufficiently exerted, and such a case is also included in the scope of the present invention. In addition, in each of the embodiments, the description of the crystal plane is (111), but it is needless to say that the same effect can be obtained even in the case of {111}.

Furthermore, the present invention can be applied not only to a semiconductor light emitting element but also to a field of electronic devices such as a light receiving element and a transistor as a semiconductor layer having a hexagonal crystal type. The present invention is not limited to the above embodiments, and can be variously modified without departing from the gist thereof.

[0064]

As described above, according to the present invention,
Since a cubic semiconductor layer having a (111) growth plane is provided below the hexagonal semiconductor layer to suppress the propagation of dislocations in the growth direction, it occurs at the interface between the substrate and the growth layer. It is possible to provide a semiconductor element which can ensure the reliability of the element by preventing the dislocation from penetrating the element heart (active layer in the case of a light emitting element).

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device to which a semiconductor element according to a first embodiment of the present invention is applied.

FIG. 2 is a schematic diagram illustrating how dislocations are eliminated in the semiconductor device of the same embodiment.

FIG. 3 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device to which a semiconductor element according to a second embodiment of the present invention is applied.

FIG. 4 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device formed on a GaAs substrate to which a semiconductor element according to a third embodiment of the present invention is applied.

FIG. 5 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device to which a semiconductor element according to a fourth embodiment of the present invention is applied.

FIG. 6 is a schematic diagram illustrating how dislocations are eliminated in the semiconductor device of the same embodiment.

FIG. 7 is a sectional view showing a schematic configuration of a GaN-based blue semiconductor laser device to which a semiconductor element according to a fifth embodiment of the present invention is applied.

FIG. 8 is a schematic diagram illustrating how dislocations are eliminated in the semiconductor device of the same embodiment.

FIG. 9 is a sectional view showing a schematic structure of a conventional GaN-based semiconductor element.

[Explanation of symbols]

10 ... Sapphire substrate (hexagonal type) 11 ... Zinc blende type n-GaN layer (crystal defect density: about 10
^{8 ~10 10} cm ^-2) 12 ... sphalerite n-GaN / n-AlGaN strained superlattice layer 13 ... wurtzite n-GaN layer 14 ... wurtzite type n-AlGaN cladding layer 15 ... wurtzite and -P GaN active layer 16 ... wurtzite p-AlGaN cladding layer 17 ... wurtzite p-GaN contact layer 18 ... p-side electrode 19 ... n-side electrode 20 ... sapphire substrate (hexagonal type) 21 ... sphalerite n-GaN layer (crystal defect density: about 10
^{8 ~10 10} cm ^-2) 22 ... sphalerite n-GaN / n-InGaN strained superlattice layer 23 ... wurtzite n-GaN layer 24 ... wurtzite n-Al _0.5 Ga _0.5 N cladding layer 25 ... Wurtzite GaN optical confinement layer 26 ... Wurtzite In _0.1 Ga _0.9 N multiple quantum well active layer 27 ... Wurtzite GaN optical confinement layer 28 ... Wurtzite p-Al _0.5 Ga _0.5 N clad layer 29 ... Wurtzite GaN contact layer 30 ... p-side electrode 31 ... n-side electrode 40 ... GaAs (111) substrate (zinc blende type) 41 ... zinc blende type n-GaN layer 42 ... zinc blende type n-InGaN / n-AlGaN strain Superlattice layer 43 ... Wurtzite n-GaN layer 44 ... Wurtzite n-AlGaN cladding layer 45 ... Wurtzite and-type InGaN active layer 46 ... Wurtzite p-AlGaN cladding layer 47 ... U Tsu blende p-GaN contact layer 48 ... current blocking layer 49 ... p-side electrode 50 ... n-side electrode 51 ... double heterostructure section 71 ... sphalerite InGaN layer 72 ... zinc blende type AlGaN layer

Claims (2)

[Claims] 1. A semiconductor device having a device portion made of a hexagonal semiconductor, wherein a cubic strain layer having a substantial {111} growth plane is provided between a growth substrate and the device portion. A semiconductor element characterized by. 2. A semiconductor device having a device portion made of a hexagonal semiconductor, wherein a growth surface having an inclination within 30 degrees from a {111} plane is substantially provided between the growth substrate and the device portion. A semiconductor device comprising a cubic strained superlattice having a {111} growth plane.