JP2000049092A - Method for growing crystal of nitride semiconductor, nitride semiconductor device, and manufacture of the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nitride semiconductor layer having less defects and dislocation by epitaxially growing a crystalline nitride semiconductor layer on a single- crystal metal nitride layer formed by nitriding a single-crystal metallic layer. SOLUTION: In a method for growing crystal of nitride semiconductor, a single-crystal insulator, single-crystal Si1-s-tGesCt (0<=s, t<=1, and 0<=s+t<=1) or A1-uBu (0<u<1 and A and B respectively represent Al, Ga, or In and As, P or Sb) semiconductor, or single-crystal metal, such as Hf, etc., is used as a single-crystal substrate 22. Then an Al1-x-yGaxIny (0<=x, y<=1, and 0<=x+y<1) is epitaxially grown on the substrate 22 as a single-crystal metallic layer 24 by using the cluster ion beam method. Thereafter, the layer 24 is nitride and a nitride layer expressed by Al1-s-tGasIntN (0ηs, t<=1, and 0<=s+t<=1) is epitaxially grown on the obtained metal nitride layer 25 at a nitride semiconductor layer 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for growing a nitride semiconductor crystal, a nitride semiconductor device, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Nitride semiconductors such as GaN, InN, and AlN are suitable as materials for use in blue semiconductor laser devices and semiconductor devices such as transistors that operate at high temperature and high speed.

Various methods have been studied to obtain a single crystal layer of a nitride semiconductor suitably used for a semiconductor device.

On a sapphire (Al ₂ O ₃ ) single crystal substrate or a Si single crystal substrate, a nitride semiconductor layer (for example, Al
N) by metalorganic vapor phase epitaxial growth (hereinafter referred to as MOV).
A technique for deposition by a PE method (also referred to as a metal organic chemical vapor deposition method (MOCVD method)) has been studied. However, the nitride semiconductor layer obtained by this method has problems such as poor surface morphology, cracks easily occurring in the nitride semiconductor layer and low yield, and has not been put to practical use. Cracks are caused by thermal stress caused by a difference in thermal expansion coefficient between the single crystal substrate and the nitride semiconductor layer in the process of lowering the temperature from the film formation temperature of the nitride semiconductor layer (about 1000 ° C. in the case of AlN) to room temperature. It is thought to occur.

[0005] Thereafter, on a sapphire single crystal substrate or a Si single crystal substrate at a relatively low temperature by MOVPE,
Once the amorphous or polycrystalline nitride semiconductor layer (Ga
N or Ga _1-a Al _a N (0 <a ≦ 1) layer),
A technique has been developed in which a buffer layer that is partially single-crystallized is formed by heating this nitride semiconductor layer, and a nitride semiconductor layer for forming a semiconductor device is epitaxially grown on this buffer layer ( For example, JP
-297023 and JP-A-7-312350).

An example of a semiconductor device using a nitride semiconductor layer formed on a buffer layer is disclosed in Japanese Patent Application Laid-Open No. H6-1774.
A light-emitting device disclosed in Japanese Patent Publication No. 23 is known.
As shown in FIG. 14, the light emitting element 900 has a buffer layer 9 made of polycrystalline or amorphous GaN or Ga _1-a Al _a N (0 <a ≦ 1) on a sapphire substrate 92.
5. n-type Ga _1-b Al _b N (0 ≦ b <1) cladding layer 9
6. n-type In _x Ga ₁ -xN (0 <x <0.5) active layer 9
7. p-type Ga _1-c Al _c N (0 ≦ c <1) cladding layer 98
Are sequentially laminated.

Further, a technique relating to the crystal growth of the buffer layer 95 is disclosed in the above-mentioned Japanese Patent Application Laid-Open Nos. 4-297523 and 7-312350. Japanese Patent Application Laid-Open Nos. H4-297023 and H7-312350
In the publication, GaN or Ga _1-a Al _a N (0 <a ≦
The buffer layer 95 of 1) is
A method of laminating at a crystal growth temperature of not less than 00 ° C and not more than 900 ° C is shown. This method uses a polycrystalline Ga _1-a Al _a
A buffer layer 95 made of N (0 ≦ a ≦ 1) is laminated on a sapphire substrate 92 at a low temperature, and a nitride semiconductor crystal layer laminated on the sapphire substrate 92 at a crystal growth temperature of about 1000 ° C. by MOVPE, for example, n-type Ga _1-b Al _b N cladding layer 9
This is to monocrystallize a part of the buffer layer 95 in the temperature raising process before the layer 6 is laminated.

[0008]

However, the inventor of the present invention has proposed that the cross section of a nitride semiconductor crystal grown on a buffer layer grown on a sapphire substrate at a low temperature by the above-mentioned conventional method can be obtained by a transmission electron microscope or the like. In detail, it was found that the nitride semiconductor crystal layer obtained by the above-described conventional crystal growth method has many dislocations, and as a result, the life of the obtained semiconductor device is short. .

In the above-described conventional method for manufacturing a semiconductor device, the buffer layer 95 is monocrystallized in the temperature increasing step before the crystal growth of the nitride semiconductor crystal layer is formed in a part of the surface of the sapphire substrate 92. Only. Accordingly, in a region where the buffer layer 95 is not single-crystallized, the orientation of the polycrystal constituting the buffer layer 95 is poor, and dislocations (defects) occur at the interface between the sapphire substrate 92 and the buffer layer 95, which is nitrided. It is considered that the compound semiconductor crystal layer (cladding layer 96, active layer 97, and cladding layer 98) grows. The density of dislocations in the nitride semiconductor crystal layer is 10 ⁹
cm ^-2 , shortening the life of the semiconductor device.

A technique for forming a buffer layer made of AlN by nitriding the surface of a sapphire single crystal substrate has also been studied (for example, Japanese Patent Application Laid-Open No. 63-1785).
No. 16), cracks occur in the buffer layer, and a large amount of dislocations occur in the buffer layer in the same manner as in the above-described prior art, and the buffer layer has not been put to practical use.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a nitride semiconductor crystal growth method for reducing dislocations in a nitride semiconductor crystal layer as compared with the prior art, and a nitride semiconductor having a long life and high reliability. It is an object to provide an apparatus and a method for manufacturing the same.

[0012]

According to the present invention, there is provided a method for growing a nitride semiconductor crystal, comprising: forming a first metal single crystal layer on a substrate; and nitriding the first metal single crystal layer. Forming a nitride single crystal layer and epitaxially growing a first nitride semiconductor layer on the metal nitride single crystal layer, thereby achieving the above object.

The step of forming the first metal single crystal layer includes:
It is preferable to include a step of preparing a single crystal substrate and a step of epitaxially growing the first metal single crystal layer on the single crystal substrate.

Preferably, the step of epitaxially growing the first metal single crystal layer is performed by a cluster ion beam method.

In one embodiment, the first metal single crystal layer is formed of Al _1-xy Ga _x In _y (0 ≦ x, y ≦ 1, 0 ≦ x
+ Y <1).

[0016] In certain embodiments, the first nitride semiconductor _{layer, Al 1-st Ga s In} t N (0 ≦ s, t ≦ 1,0
≦ s + t ≦ 1).

The step of nitriding the first metal single crystal layer includes:
Preferably, the step is a step of nitriding the first metal single crystal layer in an atmosphere containing at least hydrazine or ammonia.

The step of nitriding the first metal single crystal layer comprises:
The method may include a step of forming a metal diffusion layer on a surface of the single crystal substrate by diffusing metal atoms of the first metal single crystal layer into the single crystal substrate.

The method further includes the step of forming a second metal single crystal layer on the single crystal substrate, and the step of forming the first metal single crystal layer includes forming the first metal single crystal layer on the second metal single crystal layer. It may be a step of epitaxially growing a single crystal layer.

The step of nitriding the first metal single crystal layer includes:
The method may include forming a metal diffusion layer on the surface of the single crystal substrate by diffusing metal atoms of the second metal single crystal layer into the single crystal substrate.

The method for manufacturing a nitride semiconductor device according to the present invention comprises:
2. A method for manufacturing a nitride semiconductor device having a semiconductor multilayer structure and a pair of electrodes for applying a voltage to the semiconductor multilayer structure, wherein the step of forming the semiconductor multilayer structure includes the step of forming a nitride semiconductor according to claim 1. And a step of epitaxially growing the first nitride semiconductor layer, thereby achieving the above object.

The single crystal substrate is a conductive single crystal substrate, and the step of forming the electrodes includes forming a pair of electrodes on surfaces facing each other with the single crystal substrate and the semiconductor laminated structure interposed therebetween. It is preferably a step.

The step of epitaxially growing the first nitride semiconductor layer includes the steps of: using a semiconductor single crystal substrate as the single crystal substrate, epitaxially growing the metal single crystal layer on the semiconductor single crystal substrate; Forming the metal nitride single crystal layer by nitriding a layer, and forming a metal diffusion layer on the surface of the semiconductor single crystal substrate by diffusing metal atoms of the metal single crystal layer. You may.

In one embodiment, the single crystal substrate is a Si single crystal substrate having a (111) plane as a main surface, and the step of forming the metal single crystal layer includes the step of forming the (111) plane of the Si single crystal substrate. Al on the (111) plane as the main surface
_1-xy Ga _x In _y (0 ≦ x, y ≦ 1, 0 ≦ x + y <1)
A step of epitaxially growing a layer consisting of
The step of forming the metal nitride single crystal layer comprises the step of:
By nitriding the metal single crystal layer made of _1-xy Ga _x In _y, Al _1-xy G having a main surface of (0001) is obtained.
a step of forming the metal nitride single crystal layer consisting of a _x In _y N.

A nitride semiconductor device according to the present invention comprises: a single crystal substrate; a metal nitride single crystal layer formed from a nitrided metal single crystal layer formed on the single crystal substrate.
A semiconductor multilayer structure including a first nitride semiconductor layer epitaxially grown on the metal nitride single crystal layer; and a pair of electrodes for applying a voltage to the semiconductor multilayer structure. Achieved.

In one embodiment, a nitride semiconductor device comprises: a conductive single crystal substrate; and a metal nitride single crystal layer formed from a nitrided metal single crystal layer formed on the single crystal substrate. A semiconductor laminated structure including a first nitride semiconductor layer epitaxially grown on the metal nitride single crystal layer; and a pair of semiconductor laminated structures provided on surfaces facing each other via the single crystal substrate and the semiconductor laminated structure. Electrodes.

A first metal single crystal layer is further provided on the single crystal substrate, wherein the metal nitride single crystal layer is formed by epitaxially growing a second metal single crystal layer on the first metal single crystal layer. A configuration formed from a nitrided layer may be used.

The single crystal substrate may have a metal diffusion layer in which metal atoms of the metal nitride single crystal layer are diffused. Further, the single crystal substrate may include a metal diffusion layer in which metal atoms of the first metal single crystal layer are diffused.

The single crystal substrate is made of Si _1-st Ge _s C
_t (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1). Alternatively, the single crystal substrate is composed of A _1-u B
_u (0 <u <1), where A is A
I may be one of Ga, In and B may be one of As, P and Sb. Further, the single crystal substrate may be selected from the group consisting of sapphire, spinel, magnesium oxide, zinc oxide, chromium oxide, lithium niobium oxide, lithium tantalum oxide, and lithium gallium oxide.

In one embodiment, the first metal single crystal layer is made of Au or an alloy containing Au.

In one embodiment, the metal nitride single crystal layer is formed of Al _1-xy Ga _x In _y N (0 ≦ x, y ≦ 1, 0
.Ltoreq.x + y <1).

In one embodiment, the single crystal substrate is a Si single crystal substrate having a (111) plane as a main surface, wherein the metal nitride single crystal layer is formed on a (111) plane, and ) As the main surface.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for growing a nitride semiconductor crystal according to the present invention, first, a metal single crystal layer is formed on a substrate, and the metal single crystal layer is nitrided to form a metal nitride single crystal layer. . Thereafter, a nitride semiconductor layer is epitaxially grown on the obtained metal nitride single crystal layer. In the nitriding step, it is not necessary to nitride all of the metal single crystal layer. A part of the metal single crystal layer may be nitrided, and a nitride semiconductor layer may be epitaxially grown on the metal nitride single crystal layer formed on the surface. Further, a metal single crystal layer different from the metal single crystal layer to be nitrided may be formed on the substrate, and the metal single crystal layer to be nitrided may be formed thereon.

The metal nitride single crystal layer on which a nitride semiconductor layer is epitaxially grown functions as a conventional buffer layer and improves the crystallinity of the nitride semiconductor layer. When a buffer layer made of metal nitride is formed by nitriding a metal single crystal layer, unlike a conventional polycrystalline layer or a layer in which the polycrystalline layer is partially monocrystallized, a single crystal layer with few defects is formed. As a result, a nitride semiconductor layer having a low dislocation density can be deposited thereon by epitaxial growth.

In addition, it is possible to suppress and prevent the occurrence of cracks in the metal nitride single crystal layer or the nitride semiconductor layer formed thereon as compared with the conventional growth method.
The mechanism by which cracks are suppressed is the thermal stress generated between the metal nitride single crystal layer and the substrate or the metal single crystal layer due to the thermal history of the metal single crystal layer forming step and the metal single crystal layer nitriding step. Is reduced, the state of the interface between the substrate and the metal single crystal layer or metal nitride single crystal layer is different from the state formed by the conventional growth method,
It is assumed that the stress is relaxed or the generation of the stress is suppressed.

The metal single crystal layer can be formed by using a conventionally known method. For example, a metal single crystal layer can be formed by epitaxially growing a metal single crystal layer on a single crystal substrate by using a cluster ion beam (ICB) method or a sputtering method. A method of growing a metal single crystal layer using the ICB method (ICB apparatus and growth conditions) is described in, for example, H. Ino
kawa et al. Jpn. J. Appl. Phys. 24, (1985) pp. L173
-L174, I. Yamada et al. J. Appl. Phys. 56 (1986) p
p. 2746-2750, written by K. Yamada, edited by The Surface Science Society of Japan, "Thin Film Design Using Ion Beams", Section 5.5, pp. 90-95, Kyoritsu Shuppan, 1991 and the like. Also, a method of growing a metal single crystal layer using a sputtering method is described in S. Yokoyama et.
al. Jpn. J. Appl. Phys. 32 (1993) pp. L283-L286. In particular, by using the ICB method, a high-quality metal single crystal layer (the state of the interface with the single crystal substrate is also presumed to be good) can be formed. When the ICB method is used, a metal single crystal layer can be epitaxially grown on a single crystal substrate having a relatively large lattice mismatch (for example, about 25% or more). The above document is incorporated herein by reference as a document disclosing a method for epitaxially growing a metal single crystal layer used in the method for forming a metal single crystal layer in the embodiment of the present invention.

In the method of epitaxially growing a metal single crystal layer on a single crystal substrate, various single crystal substrates can be used. The single crystal substrate may be a dielectric (insulator) or may have conductivity (semiconductor or conductor).
By using a conductive substrate, there is an advantage that the structure of a semiconductor device can be simplified. This will be described later in detail in an embodiment of a method of manufacturing a semiconductor device.

When a nitride semiconductor device is manufactured by using the nitride semiconductor crystal growth method according to the present invention, cracks in the nitride semiconductor layer and the density of defects can be reduced. An excellent nitride semiconductor device can be manufactured.

A method for growing a nitride semiconductor crystal according to an embodiment of the present invention will be described with reference to FIGS. In the following drawings, components having the same basic functions are denoted by the same reference numerals for simplicity.

FIGS. 1A, 1B, and 1C are cross-sectional views for explaining steps of a nitride semiconductor crystal growth method according to one embodiment of the present invention.

As shown in FIG. 1A, a metal single crystal layer 24 is formed on a substrate 22. For example, a single crystal substrate is used as the substrate 22, and a metal single crystal layer is epitaxially grown on the single crystal substrate 22 by using the ICB method. The ICB method can be implemented by the method disclosed in the above-mentioned document. For example, it can be performed at room temperature in an atmosphere of about 1 × 10 ⁻⁹ Torr (about 1.4 × 10 ⁻⁷ Pa) or less. Before the epitaxial growth step, a step of cleaning the surface of the single crystal substrate 22 may be performed.

As the single crystal substrate 22, an insulator single crystal such as sapphire, spinel, magnesium oxide, zinc oxide, chromium oxide, lithium niobium oxide, lithium tantalum oxide and lithium gallium oxide, or Si _1-st Ge _s
C _t (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1) or A _1-u B
_u (0 <u <1, where A is one of Al, Ga and In, and B is one of As, P and Sb)
And a metal single crystal such as hafnium can be used. The metal single crystal layer 24 epitaxially grown on the single crystal substrate 22 is made of, for example, Al
_1-xy Ga _x In _y (0 ≦ x, y ≦ 1, 0 ≦ x + y <1)
Formed from

Next, as shown in FIG. 1 (b), the metal single crystal layer 24 is nitrided to form a metal nitride single crystal layer 25. The nitriding step can be performed by heating the metal single crystal layer 24 in a compound atmosphere containing nitrogen. As a compound containing nitrogen, hydrazine (N ₂ H ₄ )
Alternatively, ammonia (NH ₃ ) can be suitably used. In particular, hydrazine is preferable because it has a higher nitriding ability than ammonia and can shorten the nitriding time or lower the nitriding temperature.

The nitriding temperature can be appropriately set as needed.
However, the upper limit of the nitriding temperature is preferably lower than the melting point of the metal single crystal layer 24. When the metal single crystal layer 24 is heated to a temperature higher than the melting point for a long time, the metal single crystal layer 24 is melted and the crystal structure is broken, so that the metal nitride layer formed by nitriding does not become a single crystal, or becomes a crystal layer containing many dislocations. Sometimes. In order to form a high-quality metal nitride single crystal layer, it is preferable to perform nitriding at a temperature not higher than about 100 ° C. and lower than the melting point of the metal single crystal layer. There is no particular lower limit on the nitriding temperature. Since the metal nitridation reaction is an Arrhenius type reaction, the higher the nitridation temperature, the faster the nitridation proceeds. For example, the temperature for nitriding the Al _1-xy Ga _x In _y metal single crystal layer is preferably about 200 ° C. or higher when using hydrazine, and preferably about 400 ° C. or higher when using ammonia. With the above-mentioned temperature conditions, each is several tens of nm.
Can be nitrided in several tens of minutes. Since the metal nitride single crystal layer 25 obtained by nitriding the metal single crystal layer 24 is thicker than the metal single crystal layer 24, FIG. I have.

On the obtained metal nitride layer 25, a nitride semiconductor layer 26 is epitaxially grown according to a conventional method.
For example, as the nitride semiconductor layer _{26, Al 1-st Ga s} I
A layer composed of a nitride represented by n _t N (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1) can be epitaxially grown. The composition of the nitride semiconductor layer 26 and the composition of the metal nitride layer 25 may of course be different. Since the metal nitride single crystal layer 25 is a single crystal layer having few dislocations, the nitride semiconductor layer 26 epitaxially grown thereon is also a single crystal layer having few dislocations. Further, the occurrence of cracks in the metal nitride single crystal layer 25 and the nitride semiconductor layer 26 formed thereon is suppressed. For example, according to a conventional method, A single crystal
A 1N buffer layer is deposited at high temperature (about 1000 ° C.)
When a GaN layer is epitaxially grown on an N buffer layer, cracks are generated at an average interval of about 20 μm. On the other hand, according to the method of the present invention, an AlN layer is formed by nitriding an Al metal single crystal layer formed on a Si single crystal substrate. Is formed, and when the GaN layer is epitaxially grown on the AlN layer, the average distance between cracks is about 2 mm to 30 mm. The average distance between cracks generated in the nitride semiconductor layer formed according to the crystal growth method of the present invention is about 10 m.
m or more, and a semiconductor element can be manufactured with high yield.

FIGS. 2A, 2B and 2C show another embodiment of the method for growing a nitride semiconductor crystal. In this embodiment, in the nitridation step shown in FIG. 2B, the metal single crystal layer 24 is nitrided, and the metal atoms forming the metal single crystal layer 24 diffuse into the substrate 22 and the surface of the substrate 22 (Interface with metal nitride single crystal layer 25) metal diffusion layer 2
The embodiment differs from the embodiment shown in FIG. 1 in that 2a is formed.

The likelihood of the diffusion of the metal atoms depends on the combination of the material of the single crystal substrate 22 and the material of the metal single crystal layer 24. For example, as the single crystal substrate 22, Si
A single crystal substrate or A _{1-u Bu} (0 <u <1, where A is Al,
Ga and one of In, B is As, P and Sb
A semiconductor single crystal substrate represented by is one) of the, metal single crystal layer 24, an alloy containing Al or Al, and more specifically, is represented by Al _1-xy Ga _x In _y When a metal single crystal layer is used, Al atoms diffuse into the substrate 22 to easily form the metal diffusion layer 22a. For example, a metal single crystal layer 24 is formed using Al, and is subjected to a nitriding treatment at about 550 ° C. for about 1 hour, so that a metal diffusion layer 2 of about 1 nm is formed.
2a is formed.

It is considered that the metal diffusion layer 22a functions to improve the adhesiveness between the substrate 22 and the metal nitride single crystal layer 25 and to alleviate the stress caused by the difference in the coefficient of thermal expansion. Further, the contact thermal resistance between the substrate 22 and the laminated structure formed thereon can be reduced. Further, when the single crystal substrate 22 and the metal nitride single crystal layer 25 have conductivity, an ohmic contact can be formed between them by the metal diffusion layer 22a.

FIGS. 3A, 3B and 3C show another embodiment of a method for growing a nitride semiconductor crystal. In this embodiment, only a part of the metal single crystal layer 24 is nitrided in the nitriding step shown in FIG.
5 is different from the embodiment shown in FIG. The thickness of the metal single crystal layer 24 to be nitrided is
For example, it can be controlled by adjusting the nitriding time.

By forming the metal single crystal layer 24 between the single crystal substrate 22 and the metal nitride single crystal layer 25 without completely nitriding the metal single crystal layer 24, Contact thermal resistance with the laminated structure to be formed can be reduced. Further, the stress generated between the single crystal substrate 22 and the metal nitride single crystal layer 25 can be reduced by the metal single crystal layer 24. This is probably because the elastic modulus of the metal is generally lower than that of the metal nitride.

FIGS. 4A, 4B and 4C show another embodiment of the nitride semiconductor crystal growth method. In this embodiment, in the nitriding step shown in FIG. 4B, a part of the metal single crystal layer 24 is nitrided to form a metal nitride single crystal layer 25.
Is formed, and metal atoms forming the metal single crystal layer 24 diffuse into the substrate 22 to form a metal diffusion layer 22a on the surface of the substrate 22 (interface with the metal single crystal layer 24). 1 is different from the embodiment shown in FIG. As described in the embodiment shown in FIG. 2, the metal diffusion layer 22a
Is easily formed depends on the combination of the material of the single crystal substrate 22 and the material of the metal single crystal layer 24. By using the combination of materials described above and controlling the thickness of the metal single crystal layer 24 to be nitrided, FIG.
The structure shown in (b) can be obtained. The control of the thickness to be nitrided can be performed, for example, by adjusting the nitriding time as described in the embodiment shown in FIG.

FIGS. 5A, 5B, 5C and 5D show another embodiment of the method for growing a nitride semiconductor crystal.
Shown in In this embodiment, as shown in FIG.
The difference from the previous embodiment is that the method further includes a step of forming another metal single crystal layer 23 before forming the metal single crystal layer 24 to be nitrided on the substrate 22.

The metal single crystal layer 23 is formed by a known method similarly to the metal single crystal layer 24 in the above embodiment.
For example, a single crystal substrate 22 is prepared as the substrate 22, and a metal single crystal layer 23 is epitaxially grown thereon by using, for example, an ICB method. The metal material forming the metal single crystal layer 23 is Au or an alloy containing Au (for example, Au).
And an alloy of Ge and Ge). By forming an additional metal single crystal layer 23, the single crystal substrate 22
The contact thermal resistance between the layer and the laminated structure formed thereon can be reduced.

The metal single crystal layer 23 is made of Au or Au.
When formed from an alloy containing
i _1-st Ge _s C _t (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1)
Or A _{1 -u Bu} (0 <u <1, where A is Al, Ga and I
n is one of n, and B is one of As, P and Sb). In the step of nitriding the metal single crystal layer 24, the metal single crystal Layer 2
3 is diffused into the single-crystal substrate 22 to form a metal diffusion layer, so that the contact thermal resistance and the contact electric resistance between the single-crystal substrate 22 and the semiconductor multilayer structure formed thereon are reduced. it can. Some atoms constituting the metal single crystal layer 23 may be diffused, and FIGS. 6 (a) to 6 (d)
As shown in FIG. 3, in the step of nitriding the metal single crystal layer 24 to form the metal nitride single crystal layer 25, the metal single crystal layer 2
The metal diffusion layer 22a may be formed by diffusing all the atoms constituting 3 into the single crystal substrate 22. With this method, the metal single crystal layer 23 disappears (FIG. 6).
(C)). In order to make the metal single crystal layer 23 disappear by diffusion, it is preferable that the thickness of the metal single crystal layer 23 be about 3 nm or less. The temperature and time of the nitriding step of the metal single crystal layer 24 may be set in consideration of the degree of diffusion of the metal single crystal layer 23. For example, even after the nitriding reaction of the metal single crystal layer 24 is completed, the heating may be continued to promote the diffusion of the metal single crystal layer 23.

This embodiment may be combined with the previous embodiment. For example, the metal single crystal layer 23 is formed of Au or Au.
Is formed using an alloy containing
With i _{1- st} Ge _s C _t and A _1-u B semiconductor single crystal substrate 22 represented by _u, the metal atoms constituting the single crystal metal layer 23 is diffused into the semiconductor single crystal substrate 22, FIG. As in 2 (b), a metal diffusion layer 22a is formed. At this time, if the thickness of the single crystal metal layer 23 is made sufficiently thin (for example,
About 3 nm or less), all the metal atoms constituting the single crystal metal layer 23 diffuse into the single crystal substrate 22 and the single crystal metal layer 23
Can be formed without substantially remaining. In this structure, since there is no semiconductor / metal interface,
Resistance due to a Schottky barrier or the like formed at the semiconductor / metal interface can be eliminated.

Further, as described in the embodiment of FIG. 3, only a part of the metal single crystal layer 24 may be nitrided, or as described in the embodiment of FIG. 4, the metal diffusion layer 22a may be formed. At the same time, only a part of the metal single crystal layer 24 is nitrided to form the metal nitride single crystal layer 25 and the metal single crystal layer 2.
3, the metal single crystal layer 24 may be left. In any case, the effects obtained in the above embodiment can be obtained together.

Since a nitride semiconductor layer used in a semiconductor device generally has a (0001) plane as a main surface, a (00)
The main surface of the metal nitride single crystal layer is (00) such that the nitride semiconductor layer having the (01) plane as the main surface is epitaxially grown.
(01) It is preferable to form the surface. Specifically, Si _1-st Ge _s C _t (0 ≦ s, t ≦ 1, 0 ≦ s +
t ≦ 1) and A _{1−u Bu} (0 <u <1; A is one of Al, Ga and In, and B is 1 of As, P and Sb
When using a single crystal substrate formed from
(111) using a single crystal substrate having a plane major surface, thereon, (111) plane as the principal Al _1-st Ga _s In
By forming a metal single crystal composed of _t (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1) and nitriding the obtained metal single crystal layer, Al ₁₋ having a (0001) plane as a main surface is formed. _st Ga _s I
A metal nitride single crystal layer made of n _t N can be formed.

An embodiment in which a semiconductor device is manufactured by using the above-described nitride semiconductor crystal growth method will be described below. In the following embodiments, a light emitting element (semiconductor laser) is exemplified as a semiconductor device, but the present invention is not limited to the following example, and can be applied to a semiconductor device such as a field effect transistor (FET).

Embodiment 1 The light emitting device 100 according to the first embodiment of the present invention is formed using a non-conductive substrate.

Example 1-1 As shown in FIG. 7, on a sapphire substrate 22, a single-crystal AlN layer 25 having a thickness of 10 nm, an n-type Ga _0.9 Al _0.1 N cladding layer 26 having a thickness of 1 μm, A multiple quantum well (hereinafter referred to as MQW) active layer 27,
P-type Ga _0.9 Al _0.1 N clad layer 2 having a thickness of 0.5 μm
8. The p-type GaN contact layer 29 having a thickness of 0.1 μm is sequentially laminated. MQW active layer 27
Is formed by laminating 10 layers of each other such that an undoped In _0.2 Ga _0.8 N layer having a thickness of 5 nm and an undoped GaN layer having a thickness of 5 nm are alternately arranged.
_An undoped GaN layer is in contact with the side in contact with the _0.9 Al _0.1 N clad layer 26.

The semiconductor laminated structure (including the clad layer 26, the active layer 27, the clad layer 28, and the contact layer 29) formed on the single-crystal AlN layer 25 is mesa-etched, and a voltage is applied to the semiconductor laminated structure. Electrodes 32a and 32b for application are formed on the contact layer 29 and the cladding layer 26, respectively.

According to this configuration, since the single-crystal AlN layer 25 having good crystal orientation is formed immediately above the sapphire substrate 22, the sapphire substrate 22 and the single-crystal AlN layer 25 are formed.
And the density of defects and dislocations generated at the interface with n can be reduced, and n-type Ga _0.9 Al _0.1
N clad layer 26, MQW active layer 27, p-type Ga _0.9 A
l _0.1 N cladding layer 28 and GaN contact layer 29
Defects and dislocation densities can be reduced as compared with the prior art.

The light emitting device 100 is manufactured by using the crystal growth method shown in FIG. A method for manufacturing the light emitting device 100 will be described with reference to FIG.

First, an Al single crystal layer 24 is laminated on a sapphire substrate 22 by using the ICB method (FIG. 8A). Next, the Al single crystal layer 24 is nitrided to be changed to a single crystal AlN layer 25 (FIG. 8B). As a method of nitriding, the temperature of the sapphire substrate 22 is kept at 550 ° C., which is about 100 ° C. lower than 660 ° C., which is the melting point of the Al single crystal, and an appropriate gas (H ₂ carrier gas) containing a nitrogen compound such as hydrazine or ammonia is used. Then, the nitrogen component in the nitrogen compound reacts with the Al single crystal layer 24.

Then, the n-type Ga _0.9 Al _0.1 N clad layer 26 with Si addition and the MQW active layer 2 are formed by MOVPE.
7, Mg-added p-type Ga _0.9 Al _0.1 N cladding layer 28,
Mg-added p-type GaN contact layers 29 are sequentially laminated (FIG. 8C). n-type Ga _{0. 9} Al _0.1 N cladding layer 2
6, p-type Ga _0.9 Al _0.1 N cladding layer 28 and p-type G
The crystal growth temperature of the aN contact layer 29 is 1000 ° C., and the crystal growth temperature of the MQW active layer 27 is 800 ° C.

The obtained semiconductor laminated structure (layers 26, 27,
28 and 29) by etching,
The n-type Ga _0.9 Al _0.1 N cladding layer 26 is exposed. Thereafter, the p-type GaN contact layer 29 and the n-type Ga _0.9
By forming ohmic electrodes 32a and 32b respectively on the Al _0.1 N cladding layer 26,
A light-emitting element 100 is obtained. The electrode 32a is, for example, Ni /
Au and the electrode 32b can be formed by electron beam evaporation using, for example, Ti / Au.

According to this structure, the single-crystal AlN layer 25 is nitrided to form the single-crystal AlN layer 25.
The N layer 25 can be formed on the entire surface of the sapphire substrate 22 and n-type Ga
The crystallinity of the _0.9 Al _0.1 N cladding layer 26, the MQW active layer 27, the p-type Ga _0.9 Al _0.1 N cladding layer 28, and the GaN contact layer 29 can be improved.

Light Emitting Element 1 in Example 1-1 of the Present Invention
The cross section of the sample No. 00 was taken through a transmission electron microscope (hereinafter referred to as TE).
M), n-type Ga _0.9 Al _0.1
N clad layer 26, MQW active layer 27, p-type Ga _0.9 A
l _0.1 N cladding layer 28 and GaN contact layer 29
The density of defects and dislocations was 1 × 10 ⁵ / cm ² , which was found to be 1/10000 as compared with the conventional light emitting device.

(Example 1-2) In Example 1-2 of the present invention,
As shown in FIG._TwoO_Four
A single layer having a thickness of 5 nm is formed on a substrate 22 (hereinafter referred to as spinel).
Crystal Al_0.9Ga_0.1N layer 25, n-type Ga_0.9Al_0.1N
Lad layer 26, MQW active layer 27, p-type Ga _0.9Al_0.1
N-cladding layer 28 and p-type GaN contact layer 29
It is configured by lamination.

According to this configuration, the spinel substrate 22
Single crystal Al with good crystal orientation _0.9Ga_0.1N layer 25
Is formed, the spinel substrate 22 and the single crystal Al
_0.9Ga_0.1Defects or rolling occurring at the interface with the N layer 25
Can be reduced in density, and laminated on it
n-type Ga_0.9Al_0.1N clad layer 26, MQW active layer 2
7, p-type Ga_0.9Al_0.1N cladding layer 28 and GaN
Reduces the density of defects and dislocations in the contact layer 29 more than before
Can be done.

The method of manufacturing the light emitting device 100 will be described again with reference to FIG.

First, an Al _0.9 Ga _0.1 alloy single crystal layer 24 having a thickness of 5 nm is laminated on the spinel substrate 22 by using the ICB method (FIG. 8A). Next, the Al _0.9 Ga _0.1 alloy single crystal layer 24 is nitrided to be changed to a single crystal Al _0.9 Ga _0.1 N layer 25 (FIG. 8B). As a method of nitriding, maintaining the temperature of the spinel substrate 22 to 500 ° C., flowing gas containing nitrogen compounds such as hydrazine or ammonia, and a nitrogen component of nitrogen compounds in the Al _{0. 9} Ga _0.1 alloy single crystal layer 24 reaction Let it.

Thereafter, similarly to Example 1-1, the Si-added n-type Ga _0.9 Al _0.1 N clad layer 26, the MQW active layer 27, and the Mg-added p-type Ga _0.9 Al _0.1 N clad layer 2
8. A Mg-added p-type GaN contact layer 29 is sequentially laminated (FIG. 8C). The obtained semiconductor multilayer structure (layer 2
6, 27, 28 and 29) is removed by etching to expose the n-type Ga _0.9 Al _0.1 N cladding layer 26. Thereafter, the p-type GaN contact layer 29 and n
Ohmic electrodes 32a and 32b are formed on the Ga _0.9 Al _0.1 N cladding layer 26, respectively.

According to this structure, Al_0.9Ga_0.1Alloy single
The crystal layer 24 is nitrided to form single crystal Al _0.9Ga_0.1N layer 25
In order to make_0.9Ga_0.1Spinet N layer 25
Single-crystal Al
_0.9Ga_0.1N-type Ga laminated on the N layer 25_0.9Al
_0.1N clad layer 26, MQW active layer 27, p-type Ga_0.9
Al_0.1N cladding layer 28 and GaN contact layer 2
The crystallinity of No. 9 can be improved.

Light Emitting Element 1 in Example 1-2 of the Present Invention
The cross section of the sample No. 00 was observed with a TEM.
Ga _0.9 Al _0.1 N clad layer 26, MQW active layer 2
7, p-type Ga _0.9 Al _0.1 N cladding layer 28 and GaN
The density of defects and dislocations in the contact layer 29 is 1 × 10 ⁵ / c
m ² , which was 1/10000 that of a conventional light emitting device.

Light Emitting Element 100 of Embodiment 1-1 of the Present Invention
(Hereinafter referred to as light-emitting element E1), the light-emitting element 100 of Example 1-2 (hereinafter referred to as light-emitting element E2), and the conventional light-emitting element (hereinafter referred to as light-emitting element C) at a temperature of 70 ° C. FIG. 9 shows the results of the life measurement when the laser operation was performed at a lower power of 5 mW. In FIG. 9, curves E1, E2, and C represent light emitting elements E of Example 1, respectively.
1, E2, and the relationship between the operation time of the conventional light emitting element C and the change rate of the operation current. In this figure, it is known that as the rate of change ΔI / Δt of the operating current with respect to the operating time is closer to 1, the degree of deterioration of the light emitting element is smaller and the life is longer. 9 that ΔI / Δt of the light-emitting element E1 of the present invention and the light-emitting element E2 of the present invention are close to 1 even after the operation time of 10,000 hours has elapsed, but the operation time of the conventional light-emitting element C is about 5000 hours. ΔI
It has been found that the value of / Δt deviates more than 1.
From this, it was found that the light emitting element E1 of the present invention and the light emitting element E2 of the present invention have a longer life and higher reliability than the conventional light emitting element C. Note that the oscillation wavelength of each of these light-emitting elements was 420 nm.

In the above embodiment, instead of the sapphire substrate 22 or the spinel substrate 22, MgO, Zn
O, Cr ₂ O ₃ , LiNbO ₃ , LiTaO ₃ , LiGaO
The same effect can be obtained by using a single crystal substrate composed of ₂ or the like.

As described above, according to the first embodiment of the present invention, the number of defects and dislocations generated at the interface between the insulating single crystal substrate and the nitride semiconductor crystal layer is smaller than in the conventional case, and the life is longer than in the conventional case. A long and reliable semiconductor device and a method for manufacturing the same can be obtained.

In this embodiment, an example in which a light-emitting device is manufactured by using the nitride semiconductor crystal growth method shown in FIG. 1 has been described. However, various types of crystals described with reference to FIGS. Growth methods can be applied. The same effect as that of the present embodiment can be obtained by using any of the crystal growth methods described above.

(Embodiment 2) The light emitting device according to the second embodiment of the present invention is formed using a conductive substrate. The conductive substrate includes a semiconductor substrate and a conductive substrate made of metal or the like.

(Example 2-1) As shown in FIG. 10, the light emitting device 200 in Example 2-1 has an Al single crystal layer 24 having a thickness of 8 nm on an n-type Si single crystal substrate 22; A single-crystal AlN layer 25 having a thickness of 2 nm, an n-type Ga _0.9 Al _0.1 N cladding layer 26 having a thickness of 1 μm, an MQW active layer 27,
P-type Ga _0.9 Al _0.1 N clad layer 2 having a thickness of 0.5 μm
8. The p-type GaN contact layer 29 having a thickness of 0.1 μm is sequentially laminated. MQW active layer 27
Are formed so that an undoped In _0.2 Ga _0.8 N layer having a thickness of 5 nm and an undoped GaN layer having a thickness of 5 nm are alternately formed.
It has a zero-layer structure, and an undoped GaN layer is in contact with the n-type Ga _0.9 Al _0.1 N cladding layer 26.

An electrode 32a for applying a voltage to the semiconductor laminated structure (including the n-type cladding layer 26, the active layer 27, the p-type cladding layer 28 and the contact layer 29) formed on the single-crystal AlN layer 25, and 32b are formed on the contact layer 29 and the Si single crystal substrate 22 so as to face each other.

According to this structure, n-type Si single crystal substrate 2
2, an Al single crystal layer 24 having good crystal orientation is formed, and a single crystal AlN layer 25 is further formed thereon, so that the n-type Si single crystal substrate 22 and the Al single crystal layer 24 The density of defects and dislocations generated at the interface can be reduced, and the n-type Ga _0.9 Al _0.1 N clad layer 26, MQW active layer 27, p-type Ga _0.9 Al _0.1
The density of defects and dislocations in the N cladding layer 28 and the p-type GaN contact layer 29 can be reduced as compared with the conventional case. Further, heat generated in the MQW active layer 27 can be released directly through the n-type Si single crystal substrate 22. Further, since an electrode can be provided on the back surface of the n-type Si single crystal substrate 22, the number of light emitting elements obtained per substrate can be increased as compared with the conventional one, and a light emitting element which is less expensive than the conventional one can be obtained.

The light emitting device 200 is manufactured by using the crystal growth method shown in FIG. A method for manufacturing the light emitting device 200 will be described with reference to FIG.

First, on the n-type Si single crystal substrate 22, a layer thickness of 1
An Al single crystal layer 24 having a thickness of 0 nm is stacked by using the ICB method (FIG. 11A). Next, the Al single crystal layer 24 is nitrided to a depth of 2 nm from the surface to form a single crystal Al layer having a thickness of 2 nm.
It is changed to the N layer 25 (FIG. 11B). As a method of nitriding, the temperature of the n-type Si single crystal substrate 22 is maintained at 550 ° C., which is about 100 ° C. lower than 660 ° C., which is the melting point of Al, and an appropriate gas containing a nitrogen compound such as hydrazine or ammonia (H ₂ carrier gas) is used. ) Is caused to flow to cause the nitrogen component in the nitrogen compound to react with the Al single crystal layer 24.

Then, using the MOVPE method,
n-type Ga_0.9Al_0.1N clad layer 26, MQW active layer 2
7. Mg-added p-type Ga_0.9Al_0.1N cladding layer 28,
P-type GaN contact layer 29 with Mg added is sequentially laminated
(FIG. 11 (c)). n-type Ga _0.9Al_0.1N cladding layer 2
6, p-type Ga_0.9Al_0.1N cladding layer 28 and p-type G
The crystal growth temperature of the aN contact layer 29 is 1000 ° C.
The crystal growth temperature of the MQW active layer 27 is 800 ° C.
You.

Thereafter, ohmic electrodes 32a and 32b are formed on the contact layer 29 and the Si single crystal substrate 22 on the surfaces facing each other, so that the light emitting element 2 is formed.
00 is obtained. Note that the ohmic electrode 32b is
l, using Ti or Pt, etc., at 300 ° C. to 40
It can be formed by annealing at 0 ° C. The ohmic electrode 32a can be formed in the same manner as in the first embodiment.

According to this structure, Al single crystal layer 24 and single crystal AlN layer 25 are formed on the entire surface of n-type Si single crystal substrate 22 in order to nitride Al single crystal layer 24 to form single crystal AlN layer 25. The single crystal AlN layer 25
N-type Ga _{0. 9} laminated on the Al _0.1 N cladding layer 2
6. The crystallinity of the MQW active layer 27, the p-type Ga _0.9 Al _0.1 N cladding layer 28 and the p-type GaN contact layer 29 can be improved.

Light Emitting Element 2 in Example 2-1 of the Present Invention
The cross section of sample No. 00 was observed with a TEM. As a result, the n-type Ga _0.9 Al _0.1 N cladding layer 26, the MQW active layer 27, the p-type Ga _0.9 Al _0.1 N cladding layer 28, and the p-type
The density of defects and dislocations in the GaN contact layer 29 is 1 × 1
0 ⁵ / cm ^2, which is 1/100 of that of the conventional light emitting device.
00 was found.

(Example 2-2) As shown in FIG. 12, the light emitting element 300 according to Example 2-2 of the present invention has a single-crystal Al _0.9 G layer having a thickness of 5 nm on an n-type GaAs substrate 22.
a _0.1 N layer 25, n-type Ga _0.9 Al _0.1 N clad layer 2
6, an MQW active layer 27, a p-type Ga _0.9 Al _0.1 N cladding layer 28, and a p-type GaN contact layer 29 are sequentially laminated.

According to this configuration, the n-type GaAs substrate 22
The single crystal Al _0.9 Ga _0.1 N layer 25 having good crystal orientation is formed immediately above the substrate, so that defects and dislocations generated at the interface between the n-type GaAs substrate 22 and the single crystal Al _0.9 Ga _0.1 N layer 25 are formed. The density can be reduced, and defects of the n-type Ga _0.9 Al _0.1 N clad layer 26, the MQW active layer 27, the p-type Ga _0.9 Al _0.1 N clad layer 28 and the p-type GaN contact layer 29 The dislocation density can be reduced as compared with the conventional case. Also, the MQW active layer 2
7 can be dissipated directly through the n-type GaAs substrate 22. Further, since an electrode can be provided on the back surface of the n-type GaAs substrate 22, the number of light emitting elements obtained per substrate can be increased as compared with the conventional one, and a light emitting element which is cheaper than the conventional one can be obtained.

The light emitting device 300 is manufactured by using the crystal growth method shown in FIG. The method for manufacturing the light emitting element 300 will be described again with reference to FIG.

First, on the n-type GaAs substrate 22, the layer thickness is 5n.
An Al _0.9 Ga _0.1 alloy single crystal layer 24 having a thickness of m is laminated using the ICB method (FIG. 8A). Next, the Al _0.9 Ga _0.1 alloy single crystal layer 24 is nitrided to be changed to a single crystal Al _0.9 Ga _0.1 N layer 25 (FIG. 8B). As a method of nitriding, n-type G
The temperature of the aAs substrate 22 is maintained at 500 ° C., and a suitable gas (H 2) containing a nitrogen compound such as hydrazine or ammonia is used.
₂ Carrier gas) and the nitrogen component in the nitrogen compound and A
l _0.9 Ga _0.1 reacting an alloy single crystal layer 24. Thereafter, similarly to the first embodiment, the Si-added n-type Ga _0.9 Al
_{A 0.1} N clad layer 26, an MQW active layer 27, a Mg-added p-type Ga _0.9 Al _0.1 N clad layer 28, and a Mg-added p-type GaN contact layer 29 are sequentially stacked (FIG. 8).
(C)).

Thereafter, the contact layer 29 and the GaAs
By forming the ohmic electrodes 32a and 32b on the surfaces facing each other over the single crystal substrate 22, the light emitting element 300 is obtained.

According to this configuration, Al_0.9Ga_0.1Alloy single
The crystal layer 24 is nitrided to form single crystal Al _0.9Ga_0.1N layer 25
In order to make_0.9Ga_0.1N layer 25 is n-type G
The single crystal A can be formed on the entire surface of the aAs substrate 22.
l_0.9Ga_0.1N-type Ga laminated on the N layer 25_0.9A
l_0.1N clad layer 26, MQW active layer 27, p-type Ga
_0.9Al_0.1N clad layer 28 and p-type GaN contact
The crystallinity of the layer 29 can be improved.

Light Emitting Element 3 in Example 2-2 of the Present Invention
The cross section of the sample No. 00 was observed by a TEM. As a result, the n-type Ga _0.9 Al _0.1 N cladding layer 26, the MQW active layer 27, the p-type Ga _0.9 Al _0.1 N cladding layer 28 and the G type
The density of defects and dislocations in the aN contact layer 29 is 1 × 10 ⁵
/ Cm ^2, which is 1/1000 that of a conventional light emitting device.
It was found to be zero.

The light emitting device 200 of Example 2-1 of the present invention,
The results of the lifetime measurement of the light emitting element 300 according to Example 2-2 of the present invention when the laser was operated under a temperature environment of 70 ° C. and an optical output of 5 mW are shown by curves E1 and E1 in FIG.
2. Light emitting elements 200 and 30 of Example 2
0 means ΔI / Δt even after operating time of 10,000 hours
Is close to 1, but it has been found that the value of ΔI / Δt greatly deviates from 1 when the operation time of the conventional light emitting element is about 5000 hours. From this, it was found that the light-emitting element of Example 2 had longer life and higher reliability than the conventional light-emitting element. Note that the oscillation wavelengths of these light-emitting elements were all 420 nm.

In place of the n-type Si single crystal substrate 22 or the n-type GaAs substrate 22 in the above Examples 2-1 and 2-2, a semiconductor having conductivity such as an n-type GaAs substrate or an n-type SiC substrate is used. Similar effects can be obtained by using a single crystal substrate. Further, a semiconductor single crystal substrate having p-type conductivity may be used, or a conductor single crystal substrate made of metal such as hafnium may be used. Among metals, a hafnium single crystal is preferable because it has a value close to a lattice constant of a nitride semiconductor single crystal.

(Embodiment 2-3) As shown in FIG. 13, a light emitting device 400 according to Embodiment 2-3 of the present invention is sequentially laminated on an n-type GaAs substrate 22 and an n-type GaAs single crystal substrate 22. Single-crystal AlN layer 25 with a layer thickness of 5 nm, n
Ga _0.9 Al _0.1 N clad layer 26, MQW active layer 2
7, p-type Ga _0.9 Al _0.1 N cladding layer 28 and p-type G
An aN contact layer 29 is provided. A metal diffusion layer 22a is formed near the surface of the n-type GaAs substrate 22 on the single crystal AlN layer 25 side. The metal diffusion layer 22a is formed by diffusing an alloy containing Au into the n-type GaAs single crystal substrate 22.

The electrodes 32a for applying a voltage to the semiconductor laminated structure (including the n-type cladding layer 26, the active layer 27, the p-type cladding layer 28 and the contact layer 29) formed on the single crystal AlN layer 25 and 32b are formed on the contact layer 29 and the n-type GaAs substrate 22 so as to face each other.

The light emitting device 400 is manufactured by using the crystal growth method shown in FIGS.

An n-type GaAs single crystal substrate 22 having a (111) plane as a main surface is prepared. The (11) of this single crystal substrate 22
1) A single-crystal metal layer 23 having a thickness of about 1 nm and made of an alloy of Au and Ge is epitaxially grown on the surface by ICB (FIG. 6A). Obtained AuGe single crystal layer 23
Has a (111) major surface.

Next, the (111) of the AuGe single crystal layer 23
A thickness of about 20 to which about 10 ¹⁸ cm ^-3 of Si is added on the surface
The Al single crystal layer 24 of nm is epitaxially grown by using the ICB method (FIG. 6B). The obtained Al single crystal layer 24 has a (111) main surface.

The step of epitaxially growing metal single crystal layers 23 and 24 by using the ICB method includes the steps of:
3 and 24 (Au)
It is preferable to use an ICB apparatus which has a Ge source and a Si-added Al source in one chamber and can control the supply amount of the source gas from the source source using, for example, a shutter.
When such an ICB apparatus is used, a high-purity film can be grown without taking out the sample from the chamber (since there is no need to break (leak) the vacuum in the chamber). The step of epitaxially growing the metal single crystal layers 23 and 24 using the ICB method can be performed, for example, at room temperature.

Next, while the Al single crystal layer 24 is nitrided, AuGe of the AuGe single crystal layer 23 is diffused into the n-type GaAs substrate 22. The temperature of the GaAs single crystal substrate 22 is heated to a temperature (for example, 550 ° C.) lower than the melting point of the GaAs single crystal substrate 22 and the melting point of the Al single crystal layer 24, and a compound gas containing nitrogen flows into the chamber. As the compound containing nitrogen, hydrazine or ammonia is preferable. In particular, hydrazine is preferable from the viewpoint of productivity because it has a high nitriding ability and can reduce the nitriding time and / or the nitriding temperature. By nitriding for about 10 to 15 minutes, the Al single crystal layer 24 having a thickness of about 20 nm is nitrided, and an AlN single crystal layer 25 is formed. The main surface of the obtained AlN single crystal layer 25 is the (0001) plane. Since the thickness of the layer is increased by nitriding, it is shown thick in the figure. AuGe is an n-type GaAs substrate 2
2 to form an AuGe diffusion layer 22a (FIG. 6C). In order to spread AuGe,
The heating temperature and the heating time in the nitriding step may be appropriately adjusted. Even if the nitridation reaction is substantially completed, heating may be continued only for diffusion.

After that, the n-type G
a Cladding layer 26 composed of a _0.9 Al _0.1 N single crystal
Epitaxial growth is performed using the B method (FIG. 6D).
Thereafter, similarly to the other embodiments described above, the semiconductor laminated structure having the double hetero structure (the n-type cladding layer 26, the active layer 27, the p-type cladding layer 28, and the contact layer 29)
Is formed by epitaxial growth. Thereafter, the electrodes 32a and 32b are formed on the contact layer 29 and the n-type GaAs substrate 22 so as to face each other, whereby the light emitting element 40 shown in FIG.
0 is obtained. The crystal structure of the semiconductor laminated structure described above is hexagonal, and the cleavage plane of the crystal is
A laser device as t) can be formed.

The n-AlN layer 25 of the n-GaAs substrate 22
Ge atoms function as donors in the AuGe diffusion layer 22a formed near the surface on the side of n-GaAs.
The electric resistance at the interface between the s substrate 22 and the n-AlN layer 25 is reduced. Therefore, in a configuration in which the pair of electrodes 32a and 32b are arranged so as to sandwich the conductive substrate 22 and the semiconductor multilayer structure like the light emitting element 400, the operating voltage can be reduced.

Further, in Example 2-3, a p-type GaAs substrate was used as the conductive single crystal substrate 22 and the metal single crystal layer 2 was used.
If an AuNi single crystal layer is used as 3 and an Al single crystal layer to which Mg (for example, about 0.5 mol%) is added is used as the metal single crystal layer 24, the p-type AlN layer 2 is formed on the p-type GaAs substrate 22.
5, it is possible to manufacture a light-emitting element in which the arrangement of the conductivity type of the double hetero structure is reversed from the above arrangement. Further, in this inverted arrangement, an AuNi diffusion layer 22a is formed near the surface of the p-type GaAs substrate 22 on the p-type AlN25 layer side. AuNi
Since Ni in the diffusion layer functions as an acceptor, p-
The electric resistance at the interface between the GaAs substrate 22 and the p-AlN layer 25 can be reduced, and the operating voltage of the light emitting element can be reduced.

In the above embodiment, Au (simple substance) or another alloy containing Au may be used as the material of the metal single crystal layer 23.

As described above, according to the second embodiment of the present invention, a metal single crystal layer and a nitride semiconductor single crystal layer are sequentially formed immediately above a conductive single crystal substrate, and a semiconductor layer is further formed thereon. Because it is formed, heat dissipation is better than before,
The density of defects and dislocations in the semiconductor layer can be reduced. In addition, since an electrode can be provided on the back surface of the conductive single crystal substrate, a semiconductor device and a method for manufacturing the same can be obtained at lower cost than in the past.

[0111]

According to the nitride semiconductor crystal growth method of the present invention, the nitride semiconductor crystal layer is epitaxially grown on the metal nitride single crystal layer formed by nitriding the metal single crystal layer. A nitride semiconductor layer having fewer defects and dislocations than before can be obtained.

Also, by manufacturing a nitride semiconductor using the nitride semiconductor crystal growth method according to the present invention,
Thus, a nitride semiconductor device having a longer life and higher reliability than before can be obtained. The method for growing a nitride semiconductor crystal according to the present invention is suitably applied to, for example, a method for manufacturing a blue semiconductor laser.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a nitride semiconductor crystal growth method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a nitride semiconductor crystal growth method according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a nitride semiconductor crystal growth method according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a nitride semiconductor crystal growth method according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a nitride semiconductor crystal growth method according to another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a nitride semiconductor crystal growth method according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view schematically showing a light emitting device 100 according to an example of the present invention.

FIG. 8 is a cross-sectional view schematically showing a method for manufacturing the light emitting device 100 shown in FIG.

FIG. 9 is a graph showing a relationship between an operation time and a change rate of an operation current of the light emitting element of the present invention and the conventional light emitting element.

FIG. 10 is a cross-sectional view schematically showing a light emitting device 200 according to an example of the present invention.

11 is a cross-sectional view schematically showing a method for manufacturing the light emitting device 200 shown in FIG.

FIG. 12 is a sectional view schematically showing a light emitting device 300 according to an example of the present invention.

FIG. 13 is a sectional view schematically showing a light emitting device 400 according to an example of the present invention.

FIG. 14 is a cross-sectional view schematically showing a conventional light emitting device.

[Explanation of symbols]

Reference Signs List 22 substrate (single crystal substrate) 22a metal diffusion layer 23 metal single crystal layer (Au or alloy layer containing Au) 24 metal single crystal layer (Al or alloy layer containing Al) 25 metal nitride single crystal layer 26 nitride semiconductor Layer (n-type Ga _0.9 Al _0.1 N cladding layer) 27 Multiple quantum well active layer 28 p-type Ga _0.9 Al _0.1 N cladding layer 29 p-type GaN contact layer 32 a, 32 b electrode 92 sapphire substrate 95 buffer layer 96 n-type cladding layer 97 n-type active layer 98 p-type cladding layer 100, 200, 300, 400, 900 light emitting device

Claims (24)

[Claims] A step of forming a first metal single crystal layer on a substrate; a step of forming a metal nitride single crystal layer by nitriding the first metal single crystal layer; Epitaxially growing a first nitride semiconductor layer on the layer. 2. The step of forming the first metal single crystal layer includes the steps of: preparing a single crystal substrate; and epitaxially growing the first metal single crystal layer on the single crystal substrate. Item 4. The method for growing a nitride semiconductor crystal according to Item 1. 3. The method according to claim 2, wherein the step of epitaxially growing the first metal single crystal layer is performed by a cluster ion beam method. 4. The first metal single crystal layer is made of Al _1-xy G
3. The method of growing a nitride semiconductor crystal according to claim 2, wherein the nitride semiconductor is formed from a _x In _y (0 ≦ x, y ≦ 1, 0 ≦ x + y <1). 5. The semiconductor device according to claim 1, wherein the first nitride semiconductor layer is formed of Al _{1-st
Ga s In t N (0 ≦} s, t ≦ 1,0 ≦ s + t ≦ 1) nitride semiconductor method of crystal growth according to claim 4 which is formed from. 6. The step of nitriding the first metal single crystal layer is a step of nitriding the first metal single crystal layer in an atmosphere containing at least hydrazine or ammonia.
A method for growing a nitride semiconductor crystal according to claim 1. 7. The step of nitriding the first metal single crystal layer includes diffusing metal atoms of the first metal single crystal layer into the single crystal substrate, thereby forming a metal diffusion layer on the surface of the single crystal substrate. 7. The method of claim 1, further comprising the step of:
The crystal growth method for a nitride semiconductor according to any one of the above. 8. The method according to claim 8, further comprising forming a second metal single crystal layer on the single crystal substrate, wherein the forming the first metal single crystal layer includes forming the second metal single crystal layer on the second metal single crystal layer. 3. The method for growing a nitride semiconductor crystal according to claim 2, wherein the method is a step of epitaxially growing a single metal single crystal layer. 9. The step of nitriding the first metal single crystal layer includes: diffusing metal atoms of the second metal single crystal layer into the single crystal substrate to cause metal diffusion on the surface of the first single crystal substrate. 9. The method for growing a nitride semiconductor crystal according to claim 8, comprising a step of forming a layer. 10. A method for manufacturing a nitride semiconductor device having a semiconductor multilayer structure and a pair of electrodes for applying a voltage to the semiconductor multilayer structure, wherein the step of forming the semiconductor multilayer structure is performed according to claim 1. A method for manufacturing a nitride semiconductor device, comprising the step of epitaxially growing a first nitride semiconductor layer by the nitride semiconductor crystal growth method described above. 11. The single crystal substrate is a single crystal substrate having conductivity, and the step of forming the electrode includes forming a pair of electrodes on surfaces facing each other with the single crystal substrate and the semiconductor stacked structure interposed therebetween. The method for manufacturing a nitride semiconductor device according to claim 10, which is a step of forming. 12. The step of epitaxially growing the first nitride semiconductor layer comprises: using a semiconductor single crystal substrate as the single crystal substrate, epitaxially growing the metal single crystal layer on the semiconductor single crystal substrate; Forming the metal nitride single crystal layer by nitriding the single crystal layer, and forming a metal diffusion layer on the surface of the semiconductor single crystal substrate by diffusing metal atoms of the metal single crystal layer. The method for manufacturing a nitride semiconductor device according to claim 10, further comprising: 13. The method according to claim 13, wherein the single crystal substrate is a Si single crystal substrate having a (111) plane as a main surface. Al having a (111) plane as a main surface
_1-xy Ga _x In _y (0 ≦ x, y ≦ 1, 0 ≦ x + y <1)
Wherein the step of epitaxially growing a layer consisting of
By nitriding the metal single crystal layer made of _1-xy Ga _x In _y, Al _{1- xy} G having a main surface of (0001) is formed.
method of manufacturing a nitride semiconductor device according to claim 12 is a step of forming the metal nitride single crystal layer consisting of a _x In _y N. 14. A single crystal substrate, a metal nitride single crystal layer formed from a nitrided metal single crystal layer formed on the single crystal substrate, and epitaxial growth on the metal nitride single crystal layer A nitride semiconductor device, comprising: a semiconductor multilayer structure including the first nitride semiconductor layer thus formed; and a pair of electrodes for applying a voltage to the semiconductor multilayer structure. 15. A single crystal substrate having conductivity; a metal nitride single crystal layer formed from a nitrided metal single crystal layer formed on the single crystal substrate; and the metal nitride single crystal A nitride semiconductor, comprising: a semiconductor multilayer structure including a first nitride semiconductor layer epitaxially grown on a layer; and a pair of electrodes provided on surfaces opposed to each other via the single crystal substrate and the semiconductor multilayer structure. Semiconductor device. 16. The semiconductor device further comprising a first metal single crystal layer on the single crystal substrate, wherein the metal nitride single crystal layer is a second metal single crystal epitaxially grown on the first metal single crystal layer. 16. The nitride semiconductor device according to claim 14, wherein the layer is formed from a nitrided layer. 17. The nitride semiconductor device according to claim 14, wherein the single crystal substrate has a metal diffusion layer in which metal atoms of the metal nitride single crystal layer are diffused. 18. The single crystal substrate has a metal diffusion layer in which metal atoms of the first metal single crystal layer are diffused.
7. The nitride semiconductor device according to 6. 19. The method according to claim 19, wherein the single crystal substrate is made of Si _1-st Ge _s C
The nitride semiconductor device according to claim 14, wherein the nitride semiconductor device is formed from _t (0 ≦ s, t ≦ 1, 0 ≦ s + t ≦ 1). 20. The single-crystal substrate according to claim 1, wherein A _{1 -u Bu} (0 <u)
<1), where A is one of Al, Ga and In, and B is one of As, P and Sb.
19. The nitride semiconductor device according to claim 14, wherein: 21. The nitride according to claim 14, wherein the single crystal substrate is selected from the group consisting of sapphire, spinel, magnesium oxide, zinc oxide, chromium oxide, lithium niobium oxide, lithium tantalum oxide and lithium gallium oxide. Semiconductor device. 22. The nitride semiconductor device according to claim 18, wherein the first metal single crystal layer is made of Au or an alloy containing Au. 23. The metal nitride single crystal layer is formed of Al
_1-xy Ga _x In _y N (0 ≦ x, y ≦ 1, 0 ≦ x + y <
22. The nitride semiconductor device according to claim 14, which is formed from 1). 24. The single crystal substrate is a Si single crystal substrate having a (111) plane as a main surface, and the metal nitride single crystal layer is formed on a (111) plane and has a (0001) plane. 24. The nitride semiconductor device according to claim 23, wherein the surface is a plane.