JP2023096845A - Template for producing nitride semiconductor film and method for manufacturing the same - Google Patents

Abstract

To provide a template for growing a nitride semiconductor film that grows a six-fold symmetric covalent semiconductor film while maintaining a crystal structure of a substrate.SOLUTION: A template for growing a nitride semiconductor film includes a crystal structure conversion film including (A) Ga1-xInxN (0.15≤x≤0.25) composition at c plane of a ScAlMgO4 (SAM) single crystal substrate, where the crystal structure conversion film (A) is disposed at the plane of the substrate directly or via one or more other layers and mismatch in crystal growth directions at the plane of the substrate is relaxed by the crystal structure conversion film (A).SELECTED DRAWING: None

Description

Applied for application of Article 30, Paragraph 2 of the Patent Act (No. 1) Posting date of website July 7, 2021 Website address (program) https://t. co/etZkGLFyiOh https://t. co/6wXy6ckJHt (Summary of lecture) https://confit. atlas. jp/guide/event/jsap2021a/subject/13a-N101-2/advanced https://conf. atlas. jp/guide/event/jsap2021a/subject/23p-P07-3/advanced https://conf. atlas. jp/guide/event/jsap2021a/subject/13a-N101-1/advanced (Part 2) Website publication date August 26, 2021 Website address https://confit. atlas. jp/guide/event/jsap2021a/tophttps://conf. atlas. jp/guide/event/jsap2021a/static/extendedabstracts (Part 3) Publication date: August 26, 2021 Publications The 82nd JSAP Autumn Meeting Proceedings DVD (Part 4) Date: From September 10, 2021 September 23, 2021 Meeting name and venue The 82nd JSAP Autumn Meeting (online)

The present disclosure relates to a template for fabricating a nitride semiconductor film and a manufacturing method thereof.

Nitride semiconductors are used as materials for light-emitting devices and electronic devices as direct transition type wide-gap semiconductors, and are being researched and developed for new applications. A film obtained by epitaxially growing a nitride semiconductor on a single crystal substrate is used for application to these devices.

In a single crystal film grown on a substrate crystal, the presence of dislocations, which are crystal defects in the film, poses a problem when the single crystal film is applied to a device. The presence of dislocations is known to have a significant effect on device performance, such as deterioration of device characteristics and deterioration of device life.

In crystallography, the following three points are required to prevent the generation of dislocations in a single crystal film:
(1) The crystal structure of the substrate crystal and the growing film should match, and the lattice mismatch should be small.
(2) The linear expansion coefficient difference between the substrate crystal and the growing film is small.
(3) It is essential that there be no dislocations in the substrate.

For conventional gallium nitride (GaN) semiconductor films, sapphire and silicon carbide (SiC) substrates, which have a large lattice mismatch and a large difference in linear expansion coefficient, are mainly used. In recent years, GaN single crystal substrates having no lattice mismatch and the same coefficient of linear expansion have been manufactured, but this substrate has a large number of dislocations.

On the other hand, the ScAlMgO ₄ (SAM) crystal substrate is a dislocation-free crystal, and is a substrate that satisfies all of the above three conditions for not generating dislocations for GaN single crystal film growth.

In epitaxial growth on SAM substrates, lattice matching parallel to the substrate plane is considered to be important. SAM is known to be lattice-matched with, for example, InGaN at an In composition of 17% (Non-Patent Document 1), and for this reason, SAM substrates are attracting attention as substrates for growth of nitride semiconductors.

However, the present inventors have found that in GaN grown directly on a SAM substrate, irregularly shaped crystals grow on the crystal film due to the crystal surface steps in the crystal growth direction of the SAM substrate.

JP 2010-267888 A

E. S. Hellman, C. D. Brandle, E. H. Hartford Jr., Mat. Res. Soc. Symp. Proc. 395, 51 (1995)

An object of the present invention is to provide a template for growing a nitride semiconductor film for growing a six-fold symmetrical covalent semiconductor film while maintaining the crystal structure of the substrate, and a method for producing the same.

The inventors of the present invention found that a GaN film grown directly on a SAM substrate contains a cubic crystal phase, and the phenomenon of the growth of such irregularly shaped crystals on the SAM substrate is due to the crystal growth of the SAM substrate. It is clarified that it is caused by the crystal surface step in the direction. The inventors of the present invention have found that by increasing the lattice matching in the crystal growth direction, the crystal surface step can be reduced and dislocations in epitaxial growth can be reduced. Furthermore, the present inventors have made extensive studies, and have used a SAM single crystal substrate as a substrate, and provided on this substrate a crystal structure conversion film that relaxes the lattice mismatch in the crystal growth direction and is made of GaInN having a specific composition. It has been found that the above problems can be solved by The present invention has been completed through further studies based on these findings, and includes the following aspects.
Item 1.
On the c-plane of the ScAlMgO ₄ (SAM) single crystal substrate:
(A) A template for growing a nitride semiconductor film containing a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25),
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
A template for growing a nitride semiconductor film, wherein the crystal structure conversion film (A) alleviates mismatch in the crystal growth direction of the surface of the substrate.
Item 2.
moreover,
(B) contains a nitride epitaxial thin film having a composition of Al _x Ga _y In _z N (0≤x, y, z≤1, x+y+z=1);
Item 2. Nitriding according to item 1, wherein the nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate. A template for growing semiconductor films.
Item 3.
Item 3. The template for growing a nitride semiconductor film according to Item 1 or 2, wherein the crystal structure conversion film (A) has a thickness of 10 nm to 100 nm.
Item 4.
The off-angle from the c-axis to the a-axis direction and the off-angle from the c-axis to the m-axis direction of the surface of the substrate in which the mismatch in the crystal growth direction is alleviated by the crystal structure conversion film (A) 4. The template for growing a nitride semiconductor film according to any one of Items 1 to 3, wherein the temperature is 0.2° or less.
Item 5.
When the crystal structure conversion film (A) is deposited by the molecular beam epitaxy method (MBE method) and the nitride epitaxial thin film (B) is present, the nitride epitaxial thin film (B) is further deposited by the molecular beam epitaxy method. Item 5. The template for growing a nitride semiconductor film according to any one of Items 1 to 4, deposited by (MBE method).
Item 6.
Item 6. The template for growing a nitride semiconductor film according to Item 5, wherein the growth temperature is 450°C to 900°C.
Item 7.
In the template for growing a nitride semiconductor film according to any one of Items 2 to 6, the surface of the nitride epitaxial thin film (B) opposite to the substrate is directly or through one or more other layers. and a nitride semiconductor, wherein an epitaxial thin film (C) having a composition different from that of the nitride epitaxial thin film (B) is arranged.
Item 8.
On the c-plane of the SAM single crystal substrate:
(A) a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25); and (B) Al _x Ga _y In _z N (0≦x, y, z≦1, x+y +z=1) A nitride semiconductor containing a nitride epitaxial thin film having a composition of
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
The nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate,
A nitride semiconductor in which the mismatch in the crystal growth direction of the surface of the substrate is alleviated by the crystal structure conversion film (A).
Item 9.
The nitride epitaxial thin film (B) and the nitride epitaxial thin film (B) of the nitride semiconductor according to Item 8 are combined directly or via one or more other layers on the surface of the nitride epitaxial thin film (B) opposite to the substrate. a nitride semiconductor in which an epitaxial thin film (C) different in
Item 10.
On the c-plane of the SAM single crystal substrate:
(A) A method for manufacturing a template for growing a nitride semiconductor film containing a crystal structure conversion film having a Ga _1-x In _x N (0.15≦x≦0.25) composition using a molecular beam epitaxy method (MBE method). hand,
(1) A manufacturing method including a step of growing the crystal structure conversion film (A) directly or via one or more other layers on the c-plane of a SAM single crystal substrate.
Item 11.
The template for growing a nitride semiconductor film is
(B) further containing a nitride epitaxial thin film having a composition of Al _x Ga _y In _z N (0≤x, y, z≤1, x+y+z=1);
The manufacturing method is
(2) further comprising the step of growing the nitride epitaxial thin film (B) directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate; 10. The production method according to 10.

The present invention can provide a template for growing a nitride semiconductor film for growing a six-fold symmetrical covalent semiconductor film while maintaining the crystal structure and quality of the substrate.

1 is a cross-sectional view showing an example of a template for growing a nitride semiconductor film of the present invention, in which a crystal structure conversion film (A) is arranged on the c-plane of a SAM single crystal substrate; FIG. The nitride semiconductor film growth of the present invention, wherein the crystal structure conversion film (A) and the nitride epitaxial thin film (B) are arranged in this order on the c-plane of the SAM single crystal substrate so that all layers are adjacent to each other. FIG. 2 is a cross-sectional view showing an example of a template. FIG. 2 is a diagram showing a unit lattice of a SAM substrate used for a template for growing a nitride semiconductor film of the present invention; The tilt of the c-plane of the SAM substrate relaxed by the crystal structure conversion film, that is, the off-angle (θ) from the c-axis to the a-axis direction and the off-angle (θ′) from the c-axis to the m-axis direction is FIG. 4 is a diagram showing; An example of the nitride semiconductor of the present invention, in which a crystal structure conversion film (A) and a nitride epitaxial thin film (B) are arranged in this order on the c-plane of a SAM single crystal substrate so that all layers are adjacent to each other. It is a cross-sectional view showing the. A crystal structure conversion film (A), a nitride epitaxial thin film (B), and an epitaxial thin film (C) having a different composition from the nitride epitaxial thin film (B) are arranged in this order on the c-plane of the SAM single crystal substrate. 1 is a cross-sectional view showing an example of a nitride semiconductor of the present invention, in which all layers are arranged adjacent to each other; FIG. FIG. 4 is a cross-sectional view showing the mismatch of the crystal growth direction of the SAM substrate when GaN is grown on the c-plane of the SAM single crystal substrate. FIG. 2 is a diagram showing the relationship between bandgap energy (eV) and c-axis lattice constant (nm) in nitride semiconductors (GaN, AlN, and InN). When a crystal structure conversion film (A) having a Ga _1-x In _x N (0.15≦x≦0.25) composition is grown on the c-plane of a SAM single crystal substrate, the mismatch in the crystal growth direction of the SAM substrate is It is a sectional view showing. FIG. 2 is a diagram showing the relationship between bandgap energy (eV) and a-axis lattice constant (nm) in nitride semiconductors (GaN, AlN, and InN). A crystal structure conversion film (A) having a Ga _1-x In _x N (0.15≦x≦0.25) composition is grown on the c-plane of a SAM single crystal substrate, and GaN is further grown on the crystal structure conversion film (A). FIG. 10 is a cross-sectional view showing misalignment of the crystal growth direction of the SAM substrate when the SAM substrate is aligned;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, gallium nitride may be abbreviated as GaN, indium nitride as InN, aluminum nitride as AlN, aluminum gallium nitride as AlGaN, and aluminum gallium indium nitride as AlGaInN.

Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as the actual ones. Also, even when the same parts are shown, the dimensions and ratios may be different depending on the drawing.

1. Template for growth of nitride semiconductor film
The template for growing a nitride semiconductor film of the present invention comprises:
On at least one c-plane of a ScAlMgO ₄ (SAM) single crystal c-plane substrate:
(A) A template for growing a nitride semiconductor film containing a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25),
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
In the template for growing a nitride semiconductor film, the crystal structure conversion film (A) alleviates mismatch in the crystal growth direction of the surface of the substrate.

In the present invention, the thickness of each layer is determined using a transmission electron microscope.

In this specification, when referring to a relative positional relationship between two layers among a plurality of layers arranged on one surface of a substrate, one layer farther from the substrate than the substrate is referred to as " It is sometimes called the "upper" layer.

FIG. 1 shows one aspect of the template for growing a nitride semiconductor film of the present invention. In this embodiment, the crystal structure conversion film (A) is arranged directly on the c-plane of the substrate.

Further, the template for growing a nitride semiconductor film of the present invention is
Further (B) contains a nitride epitaxial thin film having a composition of Al _x Ga _y In _z N (0 ≤ x, y, z ≤ 1, x + y + z = 1),
For growing a nitride semiconductor film, wherein the nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate. It can be a template.

FIG. 2 shows one aspect of the template for growing a nitride semiconductor film of the present invention. In this embodiment, the crystal structure conversion film (A) is directly arranged on the c-plane of the substrate, and the nitride epitaxial thin film (B) is directly arranged on the surface of the crystal structure conversion film (A) opposite to the substrate. It is

1.1 ScAlMgO4 (SAM) _substrate
A template for growing a nitride semiconductor film of the present invention comprises an ScAlMgO ₄ (SAM) substrate as a substrate.

The crystal structure of SAM is trigonal, and the c-plane used for crystal growth has six-fold symmetry like nitride semiconductors (FIG. 3).

1.2 Crystal structure conversion film (A)
In the present invention, the crystal structure conversion film refers to a film that relaxes the mismatch (step height) in the crystal growth direction of the c-axis, which is the crystal growth direction of the substrate. Due to the crystal structure conversion film, the effect of reducing cubic nitrides in epitaxial growth is exhibited, and as a result, the generation of dislocations in the epitaxial thin film is suppressed.

FIG. 4 shows the inclination of the c-plane of the SAM substrate relaxed by the crystal structure conversion film, that is, the off angle (θ) from the c-axis to the a-axis direction and the off angle (θ) from the c-axis to the m-axis direction. θ′). Therefore, the smaller the value of the off-angle, the more the mismatch of the crystal growth direction of the c-plane of the SAM substrate is relaxed by the crystal structure conversion film, indicating that the crystal surface is flat.

In the present invention, the off angle (θ) of the c-plane of the SAM substrate relaxed by the crystal structure conversion film in the a-axis direction from the c-axis and the off-angle (θ′) in the m-axis direction from the c-axis are , less than or equal to 0.2°. The angle is preferably 0.15° or less, more preferably 0.1° or less, and even more preferably 0.05° or less in terms of exhibiting a superior effect of reducing dislocations in epitaxial growth.

In the present invention, the off-angle can be measured by an X-ray diffraction method.

In the present invention, the crystal structure conversion film (A) has a composition represented by Ga _1-x In _x N, and is not particularly limited as long as it is in the range of 0.15≦x≦0.25, but preferably 0.17. ≦x≦0.24, more preferably 0.19≦x≦0.23, still more preferably 0.20≦x≦0.22.

In the present invention, the crystal structure conversion film (A) has a dislocation density of 10 ⁶ /cm ² or less. It is preferably 10 ⁵ /cm ² or less, more preferably 10 ⁴ /cm ² or less, still more preferably 10 ³ /cm ² or less, from the viewpoint of exhibiting a superior effect of reducing dislocations in epitaxial growth.

In the present invention, the dislocation density of the crystal structure conversion film (A) is measured by the topography method using X-rays.

In the present invention, the thickness of the crystal structure conversion film (A) is not particularly limited, but may be, for example, in the range of 10 nm to 100 nm.

In the present invention, the crystal structure conversion film (A) can be grown using the MBE method (Patent Document 1). The MBE method includes, for example, the RF-MBE method and the ECR-MBE method. Among them, the RF-MBE method is preferred.

1.3 Nitride epitaxial thin film (B)
In the present invention, the nitride epitaxial thin film (B) is deposited on top of the crystal structure conversion film (A).

In the present invention, methods for depositing an epitaxial thin film on a surface include methods for growing an epitaxial thin film on a surface.

In the present invention, the material for the nitride epitaxial thin film (B) is not particularly limited, but examples thereof include GaN, InN, AlN, and solid solutions thereof.

In the present invention, the nitride epitaxial thin film has a dislocation density of 10 ⁸ /cm ² or less, and is preferably 10 ⁷ /cm ² or less, more preferably 10 ⁶ /cm ² or less, more preferably 10 ⁵ /cm ² or less.

In the present invention, the dislocation density of the nitride epitaxial thin film is measured by topography using X-rays.

In the present invention, the thickness of the nitride epitaxial thin film (B) is not particularly limited, but may be in the range of 100 nm to 10 nm, for example.

In the present invention, the nitride epitaxial thin film (B) is deposited using the MBE method. The MBE method includes, for example, the RF-MBE method and the ECR-MBE method. Among them, the RF-MBE method is preferred.

1.4 Other layers
In the template for growing a nitride semiconductor film of the present invention, the crystal structure conversion film (A) may be arranged on the surface of the substrate via one or more other layers, or the nitride epitaxial A thin film (B) may be disposed on the surface of the crystal structure conversion film (A) opposite to the substrate with one or more other layers interposed therebetween.

Examples of other layers include, but are not limited to, adhesive layers.

An adhesive layer is a layer that is placed between two layers adjacent to each other and that is placed between the two layers to adhere them to each other. Although the adhesive layer is not particularly limited, for example, one commonly used as an adhesive layer in nitride semiconductors can be used. The adhesive layer may consist of any one of these alone, or may consist of a plurality of types.

1.5 Use of template for growing nitride semiconductor film of the present invention
The template for growing a nitride semiconductor film of the present invention is preferably used for manufacturing nitride semiconductors and light-emitting devices and electronic devices using nitride semiconductors.

Specifically, a nitride semiconductor film is formed directly or via one or more other layers on the surface of the nitride epitaxial thin film (B) film of the template for growing a nitride semiconductor film of the present invention, which is opposite to the substrate. A nitride semiconductor can be obtained by growing it.

The composition of the nitride semiconductor film grown on the nitride epitaxial thin film (B) film of the template for growing a nitride semiconductor film of the present invention is not particularly limited. Moreover, the nitride semiconductor film may be composed of a single layer having one composition, or may be composed of a plurality of layers having different compositions.

The template for growing a nitride semiconductor film of the present invention is dislocation-free or has a reduced dislocation density, and the template for growing a nitride semiconductor film of the present invention is used as a substrate for growing a nitride semiconductor film having a small lattice mismatch. By using it, a dislocation-free or low-dislocation nitride semiconductor film can be obtained, and this film can be used to manufacture high-performance and long-life light-emitting devices, electronic devices, and the like.

2. Method for producing a template for growing a nitride semiconductor film of the present invention
In the method for producing a template for growing a nitride semiconductor film of the present invention, in addition to the crystal structure conversion film (A) and the nitride epitaxial thin film (B), at least one other film different from them is formed on the c-plane of the SAM single crystal substrate. may include the step of respectively arranging the layers of

In the nitride semiconductor film-growing template of the present invention, the crystal structure conversion film (A) is arranged on the c-plane of the SAM single crystal substrate directly or via one or more other layers. Further, in the template for growing a nitride semiconductor film of the present invention, the nitride epitaxial thin film (B) is formed directly on the surface opposite to the substrate of the crystal structure conversion film (A) or by forming one or more other layers thereon. placed through

The crystal structure conversion film (A) and the nitride epitaxial thin film (B) provided in the nitride semiconductor film growth template of the present invention are each grown under high vacuum and at a temperature of less than 1000° C. using the MBE method. . The temperature conditions are preferably 450° C. to 900° C., more preferably 450° C. to 750° C., from the viewpoint of preventing damage to the growth surface of the substrate.

3. Semiconductor of the present invention
The semiconductor of the present invention is
On at least one c-plane of a ScAlMgO ₄ (SAM) single crystal c-plane substrate:
(A) a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25); and (B) Al _x Ga _y In _z N (0≦x, y, z≦1, x+y +z=1) A nitride semiconductor containing a nitride epitaxial thin film having a composition of
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
The nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate,
In the nitride semiconductor, the crystal structure conversion film (A) alleviates the mismatch in the crystal growth direction of the surface of the substrate.

FIG. 5 shows one mode of the nitride semiconductor of the present invention. In this embodiment, the crystal structure conversion film (A) is directly arranged on the c-plane of the substrate, and the nitride epitaxial thin film (B) is directly arranged on the surface of the crystal structure conversion film (A) opposite to the substrate. It is

The semiconductor of the present invention may further contain an epitaxial thin film (C) having a composition different from that of the nitride epitaxial thin film (B).

FIG. 6 shows one mode of the nitride semiconductor of the present invention. In this embodiment, the crystal structure conversion film (A) is directly arranged on the c-plane of the substrate, and the nitride epitaxial thin film (B) is directly arranged on the surface of the crystal structure conversion film (A) opposite to the substrate. An epitaxial thin film (C) having a composition different from that of the nitride epitaxial thin film (B) is directly disposed on the surface of the nitride epitaxial thin film (B) opposite to the crystal structure conversion film (A).

3.1 Epitaxial thin films with different compositions (C)
In the present invention, the epitaxial thin film (C) having a composition different from that of the nitride epitaxial thin film (B) is grown on the nitride epitaxial thin film (B).

In the present invention, the material for the epitaxial thin film (C) is not particularly limited, but examples thereof include GaN, InN, AlN, and solid solutions thereof.

In the present invention, the thickness of the epitaxial thin film (C) is not particularly limited, but may be in the range of 100 nm to 10 nm, for example.

3.2 Other layers
In the nitride semiconductor of the present invention, the crystal structure conversion film (A) may be arranged on the surface of the substrate via one or more other layers, or the nitride epitaxial thin film (B) may be arranged on the surface of the substrate. may be arranged via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate. Further, the epitaxial thin film (C) may be arranged on the surface of the nitride epitaxial thin film (B) opposite to the crystal structure conversion film (A) via one or more other layers.

EXAMPLES The present invention will be described in more detail with reference to Examples below, but the present invention is not limited to these Examples.
<Manufacturing template for growing nitride semiconductor film>
1. Growth of modified crystal structure films on the c-plane of SAM substrates
1.1 Structural characterization of RF-MBE grown GaN on SAM substrate
SAM has a lattice mismatch with GaN and a thermal expansion coefficient difference of 1.8% and 9.8%, respectively, which are smaller than those of a sapphire substrate. In recent years, production of dislocation-free SAM single crystals has also been reported. However, the growth surface of the SAM substrate is damaged by Mg reacting with reducing gases such as hydrogen and ammonia at temperatures above 900°C. Metal-organic vapor phase epitaxy (MOCVD) and hydride vapor phase epitaxy (HVPE), which are generally used for manufacturing nitride semiconductors, are not suitable for growth.

In view of the above-mentioned problems of SAM substrates, the present inventors used the molecular beam epitaxy (MBE) method, which enables the growth of nitride epitaxial thin films in a high-vacuum environment at relatively low temperatures (450°C to 900°C). GaN film was directly grown on the SAM substrate, and an epitaxial thin film in which SAM and GaN were bonded at the atomic level was obtained. Specifically, using SAM substrates with different off-angles or step spacings (terrace widths), the effects of off-angles and step spacings on RF-MBE grown GaN on SAM substrates were investigated.

GaN was directly grown on a 10 mm square c-plane SAM substrate with an off-angle of 0.18° or 0.24° by supplying Ga and N simultaneously by the RF-MBE method. The growth conditions are growth temperature: 700° C., Ga flux: 6.33×10 ⁻⁷ Torr, nitrogen plasma power: 110 W, nitrogen flow rate: 2.0 sccm, growth time: 1 hour. Next, using a focused ion beam (FIB) from the obtained sample, the electron beam incident direction during transmission electron microscope (TEM) observation was parallel to [1-100] and [11-20] of GaN. Sectional TEM observation was performed using JEM-2100Plus (accelerating voltage: 200 kV).

Fragmentary TEM images of GaN grown directly on a SAM substrate with an off-angle of 0.18° confirmed that a flat and well-connected GaN film was grown. In addition, dislocations in the upper half of about 10 ⁹ /cm ² were present in the film. Furthermore, the selected area diffraction image revealed that hexagonal GaN was epitaxially grown on the SAM substrate. These results indicate that GaN grows coherently with a sharp interface with the SAM substrate, and that the RF-MBE method is effective for direct GaN growth on the SAM substrate.

On the other hand, in GaN grown directly on a SAM substrate with an off-angle of 0.24°, no dislocations were observed at the SAM/GaN interface. Mixture of GaN and hexagonal GaN and generation of dislocations were observed.

GaN was directly grown by RF-MBE on c-plane SAM substrates with step spacings of about 780 nm, 190 nm, or 115 nm. The growth conditions are the same as in the above experiments.

Scanning electron microscope (SEM) images of GaN grown on SAM substrates confirmed that GaN grown directly on SAM substrates with a step spacing of ~780 nm yielded the flattest films. On the other hand, in GaN grown directly on a SAM substrate with a step spacing of about 190 nm or 115 nm, it was confirmed that the film connection was poor and the presence of droplets. In addition, when the presence or absence of cubic GaN in the film was confirmed by X-ray diffraction (XRD) 2θ-ω measurement, cubic crystal A GaN peak was observed, while a cubic GaN peak was not observed for GaN grown directly on a SAM substrate with a step spacing of about 780 nm. Furthermore, the intensity ratio of the cubic GaN peak to the hexagonal GaN peak indicates that GaN grown directly on a SAM substrate with a step spacing of ~115 nm is superior to GaN grown directly on a SAM substrate with a step spacing of ~190 nm. However, it was found that more cubic GaN was mixed.

1.2 RF-MBE grown GaInN on SAM substrate
The present inventors have found that the mixture of cubic GaN and hexagonal GaN and the occurrence of dislocations in the RF-MBE grown GaN on the SAM substrate shown in 1.1 are caused by the crystal growth direction of the c-axis direction, which is the crystal growth direction. The mismatch (step height) is about 0.5 nm for the GaN unit cell and about 0.8 nm for the SAM. (Fig. 7).

From this, we found that not only in-plane lattice matching but also heightwise lattice matching is important for growing GaN films with few dislocations on SAM substrates.

Therefore, the present inventors precisely observed the initial stage of crystal growth and investigated the In composition at which the lattice in the step height direction matches in the Ga _1-x In _x N solid solution. FIG. 8 shows the relationship between the c-axis lattice constant (nm) and the bandgap energy (eV) of the nitride semiconductor. The c-axis lattice constants of GaN, AlN and InN are 0.519 nm, 0.498 nm and 0.570 nm, respectively. From this, it was found that in the GaInN solid solution, the step height of 3/2c of GaInN coincides with the step height of the SAM substrate at an In composition of 21% (Fig. 9).

This is also close to the in-plane lattice matching condition described below. FIG. 10 shows the relationship between the a-axis lattice constant (nm) and the bandgap energy (eV) of the nitride semiconductor. The a-axis lattice constants of GaN, AlN and InN are 0.319 nm, 0.311 nm and 0.355 nm, respectively. Also, the lattice constant of the a-axis of the SAM substrate is 0.325 nm. Therefore, in the GaInN solid solution, the in-plane lattices of GaInN and the SAM substrate match at an In composition of 17%.

Therefore, it is possible to grow a GaN film with few dislocations on a SAM substrate by growing a GaInN solid solution with lattice matching in the step height direction as a crystal structure conversion film on the c-plane of the SAM single crystal substrate ( Figure 11).

Claims (11)

On the c-plane of the ScAlMgO ₄ (SAM) single crystal substrate:
(A) A template for growing a nitride semiconductor film containing a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25),
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
A template for growing a nitride semiconductor film, wherein the crystal structure conversion film (A) alleviates mismatch in the crystal growth direction of the surface of the substrate. moreover,
(B) contains a nitride epitaxial thin film having a composition of Al _x Ga _y In _z N (0≤x, y, z≤1, x+y+z=1);
2. The method according to claim 1, wherein the nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate. A template for growing a nitride semiconductor film. 3. The template for growing a nitride semiconductor film according to claim 1, wherein the crystal structure conversion film (A) has a thickness of 10 nm to 100 nm. The off-angle from the c-axis to the a-axis direction and the off-angle from the c-axis to the m-axis direction of the surface of the substrate in which the mismatch in the crystal growth direction is alleviated by the crystal structure conversion film (A) 4. The template for growing a nitride semiconductor film according to claim 1, wherein is 0.2° or less. When the crystal structure conversion film (A) is deposited by molecular beam epitaxy (MBE) and the nitride epitaxial thin film (B) is present, the nitride epitaxial thin film (B) is deposited by molecular beam epitaxy. 5. The template for growing a nitride semiconductor film according to claim 1, deposited by (MBE method). 6. The template for growing a nitride semiconductor film according to claim 5, wherein the growth temperature is 450.degree. C. to 900.degree. 7. Directly or through one or more other layers on the surface of the nitride epitaxial thin film (B) opposite to the substrate of the template for growing a nitride semiconductor film according to any one of claims 2 to 6 and an epitaxial thin film (C) having a composition different from that of the nitride epitaxial thin film (B). On the c-plane of the SAM single crystal substrate:
(A) a crystal structure conversion film having a composition of Ga _1-x In _x N (0.15≦x≦0.25); and (B) Al _x Ga _y In _z N (0≦x, y, z≦1, x+y +z=1) A nitride semiconductor containing a nitride epitaxial thin film having a composition of
the crystal structure conversion film (A) is disposed on the surface of the substrate directly or via one or more other layers;
The nitride epitaxial thin film (B) is arranged directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate,
A nitride semiconductor in which the mismatch in the crystal growth direction of the surface of the substrate is alleviated by the crystal structure conversion film (A). 9. The nitride epitaxial thin film (B) of the nitride semiconductor according to claim 8 is directly or via one or more other layers on the surface of the nitride epitaxial thin film (B) opposite to the substrate, and A nitride semiconductor in which an epitaxial thin film (C) having a different composition is arranged. On the c-plane of the SAM single crystal substrate:
(A) A method for manufacturing a template for growing a nitride semiconductor film containing a crystal structure conversion film having a Ga _1-x In _x N (0.15≦x≦0.25) composition using a molecular beam epitaxy method (MBE method). hand,
(1) A manufacturing method comprising the step of growing the crystal structure conversion film (A) directly or via one or more other layers on the c-plane of the SAM single crystal substrate. The template for growing a nitride semiconductor film is
(B) further containing a nitride epitaxial thin film having a composition of Al _x Ga _y In _z N (0≤x, y, z≤1, x+y+z=1);
The manufacturing method is
(2) growing the nitride epitaxial thin film (B) directly or via one or more other layers on the surface of the crystal structure conversion film (A) opposite to the substrate; 11. The production method according to Item 10.

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