JP2000188260A - Nitride-based compound semiconductor element, crystal growth of the nitride-based compound semiconductor, and manufacture of the element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride-based compound semiconductor element, in which lattice misalignment at an interface with a substrate is relaxed. SOLUTION: This semiconductor element includes a substrate 11, a BN-based compound semiconductor buffer layer 24 on the substrate 11, and nitride-based compound semiconductor crystalline layers 34, 25 and 36 on the buffer layer 24. The substrate 11 may be made of sapphire or silicon carbide (SiC). The difference in lattice constants between those of BN and sapphire is small, and the difference in lattice constants between those of BN-based compound semiconductor and sapphire is also small. Accordingly, the BN-based compound semiconductor buffer layer 24 acts to relax lattice misalignment between the substrate 11 and semiconductor crystalline layers 34, 35 and 36. As a result, the crystallization of the semiconductor crystalline layers 34, 35 and 36 can be improved and thus light emission and electrical characteristics of the semiconductor element can be improved. The element is also high in its reliability and has long operational life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitride-based compound semiconductor device. Further, the present invention relates to a method of manufacturing the nitride-based compound semiconductor device and a method of growing a nitride-based compound semiconductor crystal used in the method of manufacturing the nitride-based compound semiconductor device. Layer composed of a BN-based compound semiconductor between an oxide-based single crystal (second solid material) (hereinafter referred to as a “BN-based compound buffer layer”)
Abbreviated. ) To form a nitride-based compound semiconductor single crystal layer having excellent crystallinity.

[0002]

2. Description of the Related Art Recently, semiconductor light emitting devices capable of emitting light in a short wavelength region (ultraviolet to green), particularly blue light, have been spotlighted. A ternary system composed of a nitride compound semiconductor such as gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), and a mixed crystal obtained by mixing these nitride compound semiconductors at a fixed ratio. A nitride-based compound semiconductor such as a quaternary system has an energy gap (forbidden band width) capable of emitting light of such a wavelength.

[0003] The crystal growth of such a nitride-based compound semiconductor mainly uses an organometallic compound CVD (MOCVD) method. The MOCVD method is a method of supplying an organic compound reaction gas into a reaction vessel in which a substrate is installed at a substrate temperature of about 900 to 1100 ° C. to epitaxially grow a thin film made of a nitride-based compound semiconductor on the substrate.
As a substrate used for crystal growth of a nitride-based compound semiconductor, a sapphire substrate and a silicon carbide (SiC) substrate are known. The reason for using a sapphire substrate or a silicon carbide (SiC) substrate is that the crystal structure is the same as that of the growing nitride-based compound semiconductor crystal and the lattice constant is relatively close.

[0004] Strictly speaking, however, there is no commercial substrate lattice-matching with a nitride-based compound semiconductor. Therefore, when a nitride-based compound semiconductor crystal is grown on the sapphire substrate or the silicon carbide (SiC) substrate by using the conventional MOCVD method, the surface morphology of the grown epitaxial layer is poor. Also, it is very difficult to obtain a crystal with high crystal perfection due to stress caused by lattice mismatch. As a result, it has been almost impossible to develop a semiconductor light emitting device that emits blue light.

To solve such a problem, FIG.
GaAl on a sapphire substrate 11 as shown in FIG.
A low-temperature growth layer 21 of N is arranged, and Ga _x Al
A structure of a semiconductor light emitting device in which a _1-x N crystal layer 31 is epitaxially grown has been proposed. The method of forming this semiconductor light emitting device is based on a method of forming a low temperature growth layer (GaAlN) at a substrate temperature T _SUB of about 400 to 900 ° C., which is much lower than a substrate temperature T _SUB (about 1000 to 1100 ° C.) used for growing a normal GaAlN crystal. Layer) 21 is grown for several tens of nm, and Ga
An AlN epitaxial layer 31 is grown. The low-temperature growth layer 21 is formed between the sapphire substrate 11 and the nitride-based compound semiconductor crystal layer 31 and is called a “buffer layer” 21 used to improve the crystallinity of the nitride-based compound semiconductor crystal layer 31. It is. The buffer layer (GaAlN buffer layer) 21 was expected to improve the surface morphology of the epitaxial layer 31 and the lattice matching between the substrate and the epitaxial layer 31. Under such expectations, development of a semiconductor light emitting device for a short wavelength region, particularly, a blue light has begun to progress.

However, in the semiconductor light emitting device having the structure shown in FIG. 9A, it is necessary to strictly control the growth conditions of the buffer layer 21. In particular, the buffer layer 21
It is necessary to set the thickness to be as thin as 0 to 50 nm, and it is necessary to control the thickness uniformly over the entire surface of the sapphire substrate 11, but it is very difficult to grow such a buffer layer 21. Therefore, in reality, the crystallinity is not improved until a semiconductor light emitting device such as a light emitting diode is manufactured. In the structure shown in FIG. 9A, a pn junction for practical use of the light emitting diode is used. Could not be realized.

Therefore, a blue light semiconductor light emitting device having a structure as shown in FIG. 9B has been proposed. In this semiconductor light emitting device, about 400 to 8
In the temperature range of 00 ° C., the GaN buffer layer 22 is
After epitaxial growth of 2 to 0.2 μm, the GaN buffer layer 22 is heated to 900 to 900 μm higher than the substrate temperature.
Ga _x Al _1-x N crystal layer 3 in a temperature range of 1150 ° C.
2 is epitaxially grown. Due to the buffer layer 22 grown at a low temperature, the lattice constant difference between the sapphire substrate 11 and the nitride-based crystal layer (Ga _x Al ₁ -xN crystal layer) 32 is reduced, and stress is reduced. Therefore, the prospect of obtaining a high-quality nitride-based compound semiconductor crystal was obtained. That is, continuous epitaxial growth to obtain a high-quality nitride-based compound semiconductor crystal capable of realizing a semiconductor light emitting device structure such as a light emitting diode (LED) or a semiconductor laser was expected. Then, the structure shown in FIG. 9B is Ga _x Al ₁ -xN
It was expected to be equally useful for buffer layers and Ga _x Al _1-x N nitride-based crystals.

However, the semiconductor light emitting device having the structure shown in FIG. 9B actually has a lattice mismatch. FIG.
FIG. 2 shows the relationship between the energy gap and the lattice constant of each material. According to this graph, sapphire is about 0.26 nm, AlN is about 0.31 nm, GaN
It can be seen that has a lattice constant of about 0.315 nm and InN has a lattice constant of about 0.35 nm. Therefore, the difference between the lattice constants of GaN and sapphire is about 0.055 nm. Such a lattice constant, when applied to an actual semiconductor light emitting device, causes a lattice mismatch between the substrate and the growth layer, and eventually causes a decrease in the crystallinity of the single crystal layer made of the nitride-based compound semiconductor. Becomes Furthermore, since the lattice constant difference between sapphire and AlN is about 0.05 nm, even if a Ga _x Al _1-x N buffer layer that is a mixed crystal of GaN and AlN is formed, the lattice constant difference is remarkable, The crystallinity of the single crystal layer made of a nitride-based compound semiconductor decreases.

On the other hand, the difference between the lattice constants of sapphire and InN is about 0.09 nm, which is larger than the difference between the two materials. Therefore, it is not desirable to form an InN buffer layer. Also, AlN, GaN, In
Similarly, the mixed crystal of the compound semiconductor composed of N also has a remarkable difference in lattice constant, indicating that it cannot be used as a buffer layer.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above points, and has been made in consideration of the above-described problems, and is directed to a material (first solid material) having a different lattice constant from a nitride-based compound semiconductor crystal layer (second solid material). It is an object of the present invention to provide a method for growing a crystal of a nitride-based compound semiconductor, which can prevent the occurrence of lattice mismatch at the interface between the substrate and the substrate for epitaxial growth.

Another object of the present invention is to provide a method for forming a nitride-based compound semiconductor crystal layer (second solid material) on a substrate such as a sapphire substrate or a silicon carbide (SiC) substrate (first solid material). An object of the present invention is to provide a crystal growth method for a nitride-based compound semiconductor that can prevent lattice mismatch with a nitride-based compound semiconductor crystal layer and improve crystallinity.

Still another object of the present invention is to provide a nitride-based compound semiconductor having a multilayer structure (second solid material) in which lattice mismatch at an interface with a substrate (first solid material) is effectively prevented. It is intended to provide an element.

Still another object of the present invention is to provide a structure in which a nitride-based compound semiconductor crystal layer (second solid material) is disposed on a substrate such as a sapphire substrate or a silicon carbide (SiC) substrate (first solid material). It is an object of the present invention to provide a nitride-based compound semiconductor device having a structure in which lattice mismatch between the substrate and the nitride-based compound semiconductor crystal layer is relaxed and the crystallinity of the nitride-based compound semiconductor crystal layer is high.

Still another object of the present invention is to provide a nitride-based compound semiconductor device having a high luminous efficiency and a long luminous life.

Still another object of the present invention is to provide a method for manufacturing a nitride-based compound semiconductor device which can prevent occurrence of lattice mismatch at an interface with an epitaxial growth substrate.

Another object of the present invention is to improve the crystallinity of a single crystal layer made of a nitride compound semiconductor by preventing the occurrence of lattice mismatch between the substrate and the crystal layer, and to provide a highly reliable nitride compound. An object of the present invention is to provide a method for manufacturing a semiconductor device.

Still another object of the present invention is to provide a method of manufacturing a nitride-based compound semiconductor device having a high luminous efficiency and a long luminous life.

[0018]

To achieve the above object, a nitride-based compound semiconductor device according to a first aspect of the present invention comprises a substrate and a BN-based compound semiconductor disposed on the substrate. It comprises at least a buffer layer and a nitride-based compound semiconductor crystal layer disposed on the buffer layer. As the substrate, a sapphire substrate, a silicon carbide (SiC) substrate, or the like can be used.

According to the nitride-based compound semiconductor device according to the first aspect of the present invention, since the buffer layer made of the BN-based compound semiconductor is provided on the substrate made of a material having a different lattice constant, The lattice mismatch between the material-based buffer layers is reduced, and the crystallinity of the nitride-based compound semiconductor single crystal layer is high. When a semiconductor light emitting device such as an LED is manufactured by improving the crystallinity, light emitting characteristics and electric characteristics are improved. In addition, since the crystallinity of the nitride-based compound semiconductor single crystal layer is improved, the reliability and operating life of the nitride-based compound semiconductor device are significantly increased.

In the nitride-based compound semiconductor device according to the first aspect of the present invention, it is preferable that the buffer layer is a semiconductor layer having a structure in which the atomic arrangement is irregular. "Structure with disordered atomic arrangement" means a "non-single-crystal state" structure such as an amorphous structure, a polycrystalline structure having small crystal grain boundaries, or a structure composed of a mixture of these. I do. It is unnecessary to explain that the amorphous structure is a structure in which the atomic arrangement is disordered. In a semiconductor layer in a poly-single crystal state, the regularity of the atomic arrangement is maintained within a certain grain range, but the regularity is disordered from a macro perspective. Disturbed structure ". The thickness of the buffer layer may be about 10 to 60 nm, and more preferably, about 20 to 30 nm.

The nitride compound according to the first aspect of the present invention
BN-based compound buffer placed on substrate of semiconductor device
Examples of layers include Ga_1-xB_xN (0 <x ≦ 1), Al
_1-xB_xN (0 <x ≦ 1), In_1-xB_xN (0 <x ≦
1), ((Al_1-yGa_y)_1-xB_x) N (0 <x ≦ 1,0
≦ y ≦ 1), ((In_1-yGa_y)_1-xB_x) N
(0 <x ≦ 1, 0 ≦ y ≦ 1), ((In_1-yAl_y)_1-x
B_x) N (0 <x ≦ 1, 0 ≦ y ≦ 1), ((In_1-yAl
_y)_1-xB_x) N (0 <x ≦ 1, 0 ≦ y ≦ 1) or ((A
L _aGa_bIn_c)_1-xB_x) N (0 <x ≦ 1, a + b + c
= 1, a, b, c ≠ 0) and the like can be used. Also, nitriding
Compound semiconductor crystal layer is composed of AlN, GaN, InN
A semiconductor is a typical example.

Further, according to a second aspect of the present invention, there is provided a method for growing a nitride-based compound semiconductor crystal, comprising the steps of: (a) preparing a substrate; and (ii) forming a BN-based compound on the substrate at a first substrate temperature. Forming at least a step of growing a semiconductor layer to form a buffer layer, and (c) epitaxially growing a nitride-based compound semiconductor crystal layer on the buffer layer at a second substrate temperature higher than the first substrate temperature. I have.

According to the method for growing a nitride-based compound semiconductor crystal according to the second aspect of the present invention, the BN-based compound buffer layer is formed on the substrate at the first substrate temperature. When the nitride-based compound semiconductor single crystal layer is epitaxially grown, lattice mismatch between the substrate and the nitride-based buffer layer can be reduced, and the crystallinity of the nitride-based compound semiconductor single crystal layer can be improved.

The buffer layer of the BN compound semiconductor has a first substrate temperature of about 200 to 1100 ° C., preferably about 50 ° C.
About 1 to 100 nm at a first substrate temperature of 0 to 600 ° C.
, Preferably about 10 to 60 nm, more preferably about 20 to 30 nm. By growing at a low first substrate temperature,
The buffer layer of the BN-based compound semiconductor is in an amorphous state or a polycrystalline state with small grains. Or about 5
B grown at a first substrate temperature of about 00 to 600 ° C.
An amorphous state and a polycrystalline state with small crystal grain boundaries are mixed in the buffer layer of the N-based compound semiconductor. In either the amorphous state or the polycrystalline state, there is no problem in serving as the buffer layer. And
The nitride-based compound semiconductor crystal layer may be epitaxially grown at a second substrate temperature of about 1000 ° C. or higher, which is higher than the first substrate temperature when the buffer layer is formed. By raising the substrate temperature to the second substrate temperature, the BN in the amorphous state
The crystallization partially progresses in the buffer layer of the compound semiconductor. A polycrystalline layer is generated at the interface between the nitride-based compound semiconductor crystal layer and the buffer layer, and a highly crystalline nitride-based compound semiconductor crystal layer can be obtained. Even when the nitride-based compound semiconductor crystal layer is grown directly from the amorphous state of the buffer layer, a lattice is formed between the amorphous buffer layer having only short-range order and the single-crystal nitride-based compound semiconductor crystal layer. Since no mismatch occurs, a nitride-based compound semiconductor crystal layer having high crystallinity can be obtained.

In the crystal growth method for a nitride-based compound semiconductor according to the second aspect of the present invention, the nitride-based compound semiconductor crystal layer may be made of AlN, GaN, InN, or the like.

Further, a nitride-based compound semiconductor device according to a third aspect of the present invention includes a first layer made of a first solid material,
A second layer made of a second solid material having a nitride-based compound semiconductor crystal structure having a different lattice constant from the first solid material;
It comprises a buffer layer made of a BN-based compound semiconductor for lattice-matching the first layer and the second layer arranged between the first layer and the second layer. As the first solid material, a solid material (substance) such as sapphire or silicon carbide (SiC) is suitable.

According to the nitride-based compound semiconductor device according to the third aspect of the present invention, the second solid material is different from the buffer made of the BN-based compound semiconductor on the substrate made of the first solid material having a different lattice constant. Since the layer includes the layer, lattice mismatch between the first solid material and the second solid material (nitride-based compound semiconductor crystal) is reduced, and the second solid material (nitride-based compound semiconductor crystal) has high crystallinity. Then, when a semiconductor light emitting device such as an LED is manufactured by improving the crystallinity, the light emission characteristics and the electric characteristics are improved, and the crystallinity of the second solid material (nitride-based compound semiconductor crystal) is improved. Therefore, the reliability and operating life of the nitride-based compound semiconductor device are greatly increased.

Further, according to a fourth aspect of the present invention, there is provided a nitride-based compound semiconductor device comprising a substrate and a BN disposed on the substrate.
A buffer layer comprising a compound semiconductor, an n-type nitride-based compound semiconductor crystal layer disposed on the buffer layer, and n
An active layer composed of a nitride-based compound semiconductor crystal disposed on the p-type nitride-based compound semiconductor crystal layer, a p-type nitride-based compound semiconductor crystal layer disposed on the active layer, and applying a voltage to the active layer And a first electrode and a second electrode. As the substrate, a sapphire substrate or a silicon carbide (SiC) substrate is preferable. The active layer is made of an intrinsic nitride-based compound semiconductor crystal to which no impurity is intentionally added (doped), and emits light when an operating voltage is applied. Here, as the “nitride-based compound semiconductor element”, an LED, a semiconductor laser, a transistor, or the like can be applied. For LEDs and semiconductor lasers,
The “electrode” is one of an anode electrode (p-electrode) and a cathode electrode (n-electrode). "Second electrode"
This means that in an LED or a semiconductor laser, either an anode electrode (p-electrode) or a cathode electrode (n-electrode) that does not become the first electrode. If the “nitride-based compound semiconductor device” of the present invention is a bipolar transistor (BJT), the “first electrode” is one of the emitter electrode or the collector electrode, and the “second electrode” is the second electrode. Either the emitter electrode or the collector electrode area which is not one electrode. The “nitride-based compound semiconductor device” of the present invention is a HEMT, MESFET,
In the case of SIT, the “first electrode” is one of a source electrode and a drain electrode, and the “second electrode” is one of a source electrode and a drain electrode that does not become the first electrode.

According to the nitride-based compound semiconductor device of the fourth aspect of the present invention, the sapphire substrate or the silicon carbide (Si)
C) Since the BN-based compound buffer layer is provided on a substrate such as a substrate made of a material having a different lattice constant, lattice mismatch between the substrate and the nitride-based buffer layer is reduced. Therefore, the respective crystals of the n-type nitride-based compound semiconductor crystal layer, the active layer and the p-type nitride-based compound semiconductor crystal layer have high integrity. For this reason, when a semiconductor light emitting device such as an LED is manufactured, light emitting characteristics and electrical characteristics are improved. Further, since the crystallinity of each of the n-type nitride-based compound semiconductor crystal layer, the active layer, and the p-type nitride-based compound semiconductor crystal layer is improved, the reliability is high and the operation life is long.

In the nitride-based compound semiconductor device according to the fourth aspect of the present invention, it is preferable that the buffer layer is a semiconductor layer having a structure in which the atomic arrangement is irregular. As described in the first feature, the “structure having disordered atomic arrangement” refers to “a structure such as an amorphous structure, a polycrystalline structure having small crystal grain boundaries, or a structure including a mixture thereof. "Non-single crystal state" structure. The thickness of this buffer layer is 10 to 60 nm, preferably 20 to 60 nm.
It can be selected to be about 30 nm. The BN-based compound semiconductor forming the buffer layer is, for example, AlN,
It can be composed of a mixed crystal of a compound semiconductor such as GaN or InN and BN.

The n-type nitride-based compound semiconductor crystal layer or the p-type nitride-based compound semiconductor crystal layer is formed of an n-type impurity element or a p-type nitride semiconductor.
, GaN, In doped with a p-type impurity element
With an N-compound semiconductor or the like, the intrinsic nitride-based compound semiconductor crystal layer can be composed of a compound semiconductor crystal such as AlN, GaN, or InN. Further, the n-type nitride-based compound semiconductor crystal layer, the p-type nitride-based compound semiconductor crystal layer, and the intrinsic nitride-based compound semiconductor crystal layer are made of AlN, GaN, InN.
Ternary system containing these or 4
It is also possible to use a base nitride-based compound semiconductor crystal layer. The active layer is at least one quantum well (QW)
May be included. The quantum well (QW) adjusts its forbidden band energy by changing the composition ratio of elements constituting each of the adjacent nitride-based compound semiconductor crystal layers, and forms a heterojunction by joining layers having different forbidden band energies. Can be formed. Alternatively, a heterojunction may be formed by a first layer forming an energy barrier and a second layer in which the composition ratio of the constituent elements of the first layer is changed to form a predetermined potential profile.

When the substrate is made of an insulating sapphire substrate, the n-electrode is disposed on the n-type nitride-based compound semiconductor layer from which a part has been removed. On the other hand, when the substrate is made of SiC, which is a conductor, the n-electrode can be formed on the back surface of the substrate.

Further, a method for manufacturing a nitride-based compound semiconductor device according to a fifth aspect of the present invention includes the steps of (a) preparing a substrate, and (b) forming a BN-based compound on the substrate at a first substrate temperature. (C) forming a buffer layer by epitaxially growing the semiconductor layer and (c) forming an n-type nitride-based compound semiconductor crystal layer on the buffer layer at a second substrate temperature higher than the first substrate temperature; a step of growing a nitride-based compound semiconductor crystal on the n-type nitride-based compound semiconductor crystal to form an active layer; and (e) a step of forming a p-type nitride-based compound semiconductor crystal layer on the active layer. (F) forming a first electrode and a second electrode for applying a voltage to the active layer.

According to the method of manufacturing a nitride-based compound semiconductor device according to the fifth aspect of the present invention, the buffer layer of the BN-based compound semiconductor is grown at a low first substrate temperature of about 200 to 1000 ° C. Becomes an amorphous state or a polycrystalline state with small grains. Alternatively, an amorphous state and a polycrystalline state having small crystal grain boundaries are mixed in the buffer layer of the BN-based compound semiconductor grown at the first substrate temperature. The first substrate temperature is more preferably from 500 to 600C. Then, the n-type nitride-based compound semiconductor crystal layer is set at a temperature higher than the first substrate temperature when the buffer layer is formed.
By performing epitaxial growth at a second substrate temperature of 000 ° C. or higher, the BN-based compound semiconductor buffer layer in an amorphous state partially undergoes crystallization. A polycrystalline layer is generated at the interface between the n-type nitride-based compound semiconductor crystal layer and the buffer layer, and a nitride-based compound semiconductor crystal layer having high crystallinity can be obtained. Even when the n-type nitride-based compound semiconductor crystal layer is grown directly from the amorphous state of the buffer layer, an amorphous buffer layer having only short-range order and an n-type nitride-based compound semiconductor in a single crystal state Since no lattice mismatch occurs between crystal layers, a nitride-based compound semiconductor crystal layer having high crystallinity can be obtained. Therefore, it is possible to manufacture a nitride-based compound semiconductor device while maintaining high quality crystallinity of the active layer and the p-type nitride-based compound semiconductor crystal layer thereon. For this reason, it is possible to manufacture a semiconductor light emitting device such as an LED while improving the light emitting characteristics and the electric characteristics. Further, since the crystallinity of each of the n-type nitride-based compound semiconductor crystal layer, the active layer, and the p-type nitride-based compound semiconductor crystal layer is improved, a semiconductor device having high reliability and a long operating life can be manufactured. is there.

The nitride-based compound semiconductor crystal layer of the nitride-based compound semiconductor device according to the fifth aspect of the present invention is composed of AlN,
GaN, InN, or the like can be employed, and a ternary or quaternary compound semiconductor crystal layer made of a mixed crystal thereof may be used. The n-type nitride-based compound semiconductor crystal layer is formed by adding C, Si, Ge, Se, S, S
What is necessary is just to dope an impurity element, such as n, Te, Be. Further, the p-type nitride-based compound semiconductor crystal layer is formed by adding Mg, Zn, Cd, Be, Ca, S
An impurity element such as r or Ba may be doped.

Further, according to a sixth aspect of the present invention, there is provided a nitride-based compound semiconductor device comprising: a buffer layer formed of a BN-based compound semiconductor disposed on a substrate; and a nitride-based compound semiconductor disposed on the buffer layer. And a first electrode and a second electrode for applying a voltage to the laminate having a pn junction structure.

The nitride-based compound semiconductor device according to the sixth aspect of the present invention is characterized in that BN is formed on a substrate made of a material having a different lattice constant, such as a sapphire substrate or a silicon carbide (SiC) substrate.
Since the compound compound buffer layer is provided, when epitaxially growing a laminate having a pn junction structure made of a nitride compound semiconductor, lattice mismatch with the substrate is reduced,
The crystallinity of the laminate having a pn junction structure is high, the number of crystal defects is small, and the surface morphology is good. For this reason, when a semiconductor light emitting device such as an LED is formed by a laminate having a pn junction structure, the luminous efficiency is high and the electrical characteristics are good. Further, since the crystallinity of the laminate having the pn junction structure is good, the reliability is high and the operating life is long.

Further, in the method for manufacturing a nitride-based compound semiconductor device according to the seventh aspect of the present invention, (a) a BN-based compound semiconductor layer is epitaxially grown on a substrate at a first substrate temperature to form a buffer layer. (B) forming a laminate of a pn junction structure made of a nitride-based compound semiconductor on the buffer layer at a second substrate temperature higher than the first substrate temperature; and (c) pn Forming a first electrode and a second electrode for applying a voltage to the laminate having the bonding structure. As described in the second aspect, the first substrate temperature is about 200 to 1100
C., preferably about 500-600 C., and the second substrate temperature is about 1000 C. or more. By growing at a low first substrate temperature, the buffer layer of the BN-based compound semiconductor has an amorphous state, a polycrystalline state, or a structure in which the amorphous state and the polycrystalline state are mixed. By increasing the substrate temperature to the high second substrate temperature, the buffer layer of the amorphous BN-based compound semiconductor partially crystallizes. A polycrystalline layer is generated at the interface between the nitride-based compound semiconductor crystal layer and the buffer layer, and a pn junction structure composed of the nitride-based compound semiconductor crystal layer having high crystallinity can be obtained. Even when the nitride-based compound semiconductor crystal layer is grown directly from the amorphous state of the buffer layer, a lattice is formed between the amorphous buffer layer having only short-range order and the single-crystal nitride-based compound semiconductor crystal layer. Since no mismatch occurs, a pn junction structure including a nitride-based compound semiconductor crystal layer having high crystallinity can be obtained.

According to the method for manufacturing a nitride-based compound semiconductor device according to the seventh aspect of the present invention, the crystallinity of the stacked body having the pn junction structure is improved. Characteristics and electrical characteristics are improved. Furthermore, p-
Since the crystallinity of the n-junction structure is improved, the reliability and operating life of the nitride-based compound semiconductor device are significantly increased.

Further, in the nitride compound semiconductor device according to the eighth aspect of the present invention, a buffer layer composed of a BN compound semiconductor disposed on a substrate and a light emitting region formed on the buffer layer are formed. A first compound electrode for applying a voltage to the light emitting region;
And at least electrodes.

According to an eighth aspect of the present invention, there is provided a nitride-based compound semiconductor device on a substrate made of a material having a different lattice constant, such as a sapphire substrate or a silicon carbide (SiC) substrate.
Since the substrate buffer layer is provided, lattice mismatch between the substrate and the nitride buffer layer is reduced, and the crystallinity of the light emitting region is good. Therefore, the light emitting characteristics and electrical characteristics of the semiconductor light emitting device are improved. In addition, since the crystal in the light emitting region has high integrity, the nitride-based compound semiconductor device has high reliability and a long operating life.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The most basic object of the present invention is to provide a nitride-based compound semiconductor on a surface of an epitaxial growth substrate made of a material having a different lattice constant from that of a nitride-based compound semiconductor. An object of the present invention is to provide a method for epitaxially growing a single crystal. The difference in lattice constant between the substrate material and the compound semiconductor epitaxial growth layer causes lattice mismatch at the interface. Therefore, in order to epitaxially grow a high-quality nitride-based compound semiconductor crystal,
A buffer layer that matches the lattice constant between the substrate material and the compound semiconductor epitaxial growth layer should be formed.

In the present invention, a BN-based compound semiconductor is used instead of the compound semiconductor used as a conventional buffer layer for lattice matching. Figure 8 shows the lattice constant of BN.
Approximately 0.24 nm as shown in FIG. Therefore, there is a difference in lattice constant of about 0.02 nm from sapphire mainly used as a substrate. This value is much smaller than the lattice constant difference between the compound semiconductor used as a conventional buffer layer and the sapphire substrate. Therefore, BN and Al
All ternary compound semiconductors composed of AlBN which is a compound (mixed crystal) with N, GaAlN which is a mixed crystal of BN and GaN, and InBN which is a mixed crystal of BN and InN, are all used.
It has only a small lattice constant difference from the sapphire substrate.

Further, a ternary or quaternary compound composed of a mixed crystal of two or more compound semiconductors selected from AlN, GaN and InN and a quaternary or quinary compound composed of a mixed crystal of BN and BN. Even if a buffer layer is formed with a system compound semiconductor,
The difference in lattice constant is smaller than that of a conventionally used compound semiconductor buffer layer. Therefore, even if these quaternary or more compound semiconductors are used, it is possible to greatly reduce lattice mismatch between the substrate and the epitaxial growth layer.

An embodiment of the present invention will be described with reference to a nitride-based compound semiconductor device having a sectional structure shown in FIG. The buffer layer 23 disposed on the sapphire substrate 11 is made of a ternary compound semiconductor of (Ga ₁ -xB _x ) N, on which a single-crystal GaN crystal layer 33 is grown.

A method of forming a nitride-based compound semiconductor device having the structure shown in FIG. 1 employs a method of growing using a two-stage temperature profile at a first substrate temperature T _SUB1 and a second substrate temperature T _SUB2 . ing. That is, (G) is first placed on the sapphire substrate 11 at the low first substrate temperature T _SUB1 .
The a _{1-x B x)} N buffer layer 23 is epitaxially grown. Thereafter, Ga is further added on the buffer layer 23 at a second substrate temperature T _SUB2 higher than the first substrate temperature T _SUB1.
An N crystal layer 33 is grown. The (Ga _1-x B _x ) N buffer layer 23 can be formed to a thickness of about 1 to 100 nm, preferably about 10 to 60 nm, and more preferably about 2 to 60 nm.
A thickness of 0 to 30 nm is more preferred. Furthermore, (Ga _1-x
B _x ) The first substrate temperature T _SUB1 for growing the N buffer layer 23 is about 200 to 1000 ° C. In particular,
A substrate temperature T _{SU B1} of about 500-600 ° C. is preferred.

The (Ga _1-x B _x ) N buffer layer 23 and the nitride-based compound semiconductor crystal layer 33 can be epitaxially grown by a general semiconductor device growth method. The following is a description of a method for growing a nitride-based compound semiconductor crystal of the present invention by applying this general method for growing a semiconductor device.

[0048] (a) First, in the low substrate temperature T _SUB about 500 to 600 ° C., be grown the _{(Ga 1-x B x)} N layer, the _{(Ga 1-x B x)} N layer It becomes an amorphous state.
The (Ga _1-x B _x ) N buffer layer 23 in such an amorphous state is partially crystallized by gradually increasing the substrate temperature T _SUB to about 1000 ° C. or higher. In particular,
The sapphire substrate 11 is introduced and installed in the reaction vessel, and controlled by a mass flow controller (MFC) or the like.
Organometallic compound gas (MO gas) as a group V source gas and ammonia (N
H ₃ ) gas together with a carrier gas is applied to the sapphire substrate 1
1 to grow a desired crystal layer epitaxially. In this case, first, a source gas (source gas) to which boron (B) is added is supplied onto the sapphire substrate 11, and the substrate temperature T _SUB is raised to 500 to 600 ° C. Then, a buffer layer 23 made of a compound of (Ga ₁ -xB _x ) N is formed on the sapphire substrate 11 while maintaining the substrate temperature T _SUB at 500 to 600 ° C.

(B) After growing the buffer layer 23, the temperature in the reaction vessel is gradually increased, and at a substrate temperature T _SUB of about 1000 ° C. or more, a group III source gas (source gas) to which boron (B) is not added. ) And an ammonia (NH ₃ ) gas as a group V source gas are supplied to the surface of the sapphire substrate 11 together with a carrier gas to epitaxially grow the GaN crystal layer 33. As the substrate temperature T _SUB rises, the crystallization of the (Ga _1-x B _x ) N buffer layer 23 in the amorphous state partially progresses. The rise of the substrate temperature T _SUB is (Ga _1-x B _x ) N
Activation energy is given to the constituent elements (atoms) of the buffer layer 23, and each atom is moved to a lattice point by the activation energy, and crystallization proceeds. However, in practice, such a crystallization process cannot produce a complete single crystal state. Since crystallization progresses locally, the buffer layer 23 has a polycrystalline structure with small crystal grain boundaries. This polycrystal acts as a seed crystal when forming the GaN crystal layer 33 on the buffer layer 23. That is, about 1000 ° C
When GaN is epitaxially grown at the above substrate temperature T _SUB , a GaN single crystal layer is uniformly formed from the seed crystal.

A substrate temperature T _SUB of about 200 to 1000 ° C.,
Preferably, the (Ga ₁ -xB _x ) N buffer layer 23 grown at a substrate temperature T _SUB of about 500 to 600 ° C. may not be in an amorphous state but in a polycrystalline state with small grains. Whether an amorphous state or a polycrystalline state depends on the growth conditions of the (Ga _1-x B _x ) N layer, whichever functions as the buffer layer 23. There is no problem to fulfill. (Ga in the amorphous state
_{Even when the 1-x} B _x ) N buffer layer 23 is grown, the substrate temperature T _{SUB is then} increased to grow the GaN crystal layer 33.
Raises the interface with the GaN crystal layer 33 (G
a _1-x B _x ) Since a polycrystalline layer is formed on the surface of the N buffer layer 23, a GaN crystal layer 33 having high crystallinity can be obtained. Even when the GaN crystal layer 33 is grown directly from the amorphous state of the (Ga _1-x B _x ) N buffer layer 23, the (Ga _1-x B _x ) N
_1-x B _x ) Since the lattice mismatch does not occur between the N buffer layer 23 and the single crystal GaN crystal layer 33, G
An aN crystal layer 33 can be obtained.

The (Ga _1-x B _x ) N buffer layer 23 grown at a low substrate temperature T _SUB of about 500 to 600 ° C. has an amorphous state and a polycrystalline state with a small grain boundary. Are mixed. Such an amorphous or polycrystalline buffer layer 23 enables a uniform single crystal layer to be epitaxially grown thereon. Furthermore, the buffer layer 23 for epitaxially growing a single crystal layer with high crystal perfection must be lattice-matched with the single crystal layer at the interface. Good lattice matching with the layer. Therefore, the buffer layer of the present invention is a “semiconductor layer having a structure with disordered atomic arrangement”, that is, an amorphous semiconductor layer or a polycrystalline semiconductor layer. In a semiconductor layer in a polysingle crystal state, the regularity of the atomic arrangement is maintained within a certain grain range, but the regularity is disturbed from a macro perspective.
This can be described as a “non-single-crystal state” semiconductor layer.

In the embodiment of the present invention, a ternary or higher compound semiconductor, which is a mixed crystal in which BN is added, is used as a buffer layer in a compound semiconductor which has been conventionally used as a buffer layer. By using such a buffer layer made of a ternary or higher compound semiconductor containing BN (hereinafter abbreviated as "BN-based compound buffer layer"), a BN-based compound buffer layer and a single epitaxially grown BN-based compound buffer layer are formed. Lattice mismatch with the crystal layer is further reduced. As shown in FIG. 8, a compound semiconductor conventionally used mainly as a buffer layer, for example, Al
The lattice constant difference between BN and the sapphire substrate is much smaller than the lattice constant difference between the compound semiconductor such as N, GaN, and InN and the sapphire substrate. Therefore, the lattice constant difference between the buffer layer made of a BN-based compound semiconductor containing BN as a mixed crystal and the single crystal layer epitaxially grown thereon is reduced, and the lattice mismatch is reduced. As a result, a crystal layer with high crystal perfection can be formed.

Further, the use of a BN-based compound semiconductor containing BN as a mixed crystal causes an increase in the softness of the buffer layer. BN having a hexagonal crystal structure or a wurtz crystal structure has characteristics such that, compared to other materials, it has high flexibility and easy impurity doping. Therefore, if a certain ratio of BN is added to a compound semiconductor conventionally used as a buffer layer to form a ternary or quaternary mixed crystal, the softness of the compound semiconductor increases. This increase in softness further reduces the difference in lattice constant between the substrate and the single crystal layer epitaxially grown thereon. Therefore, it becomes possible to obtain a single crystal layer which is more excellent in crystallography.

Table 1 shows that when the conventional GaN buffer layer and the (Ga _1-x B _x ) N buffer layer of the present invention were used,
The comparison of the characteristics of the GaN single crystal layer epitaxially grown on the buffer layer was shown.

[0055]

[Table 1] In the comparison of Table 1, the GaN buffer layer and Ga _1-x B _x
All N buffer layers (x = 0.05) are grown at about 550 ° C. to a thickness of about 30 nm. The GaN crystal layer on the buffer layer is an n-type single crystal layer,
It is epitaxially grown to a thickness of μm.

As shown in Table 1, the GaN single crystal layer epitaxially grown on the GaN buffer layer
While having an electron mobility of about m ² / Vs, Ga _{1 -x}
B _x N buffer layer arranged GaN crystal layer on has a electron mobility of about 340m ² / Vs. That is, Ga _1-x
It is the electron mobility in the case of forming a GaN crystal layer on the B _x N buffer layer is increased. Such an increase in electron mobility is due to a decrease in defects in the GaN crystal layer, which is because when electrons travel in the GaN crystal layer, scattering phenomena due to defects are reduced.

Therefore, when a semiconductor light emitting device such as a semiconductor laser or an LED is manufactured, the mobility of electrons in the n-type GaN crystal layer and the p-type GaN crystal layer epitaxially grown on the buffer layer is improved, and Luminous efficiency is improved.

Further, the full width at half maximum (FWH) measured by DXRD
M) decreased from 550 seconds (arcsec) to about 400 seconds (arcsec). Accordingly, the displacement of atoms at lattice points of the GaN crystal layer is reduced, which means that the crystallinity of the GaN crystal layer is improved. The electron density is 3.2 × 10 ¹⁷
cm ⁻³ to 2.46 × 10 ¹⁷ cm ⁻³ .

Table 2 shows that Ga having a different composition ratio of boron (B) was used.
The electron mobility, full width at half maximum (FWHM), and electron density characteristics of the GaN crystal layer when the _1-x B _x N buffer layer was grown are shown, and FIGS. 6A and 6B show the table. 2 is a graph showing the dependence of electron mobility and full width at half maximum (FWHM) on the composition ratio of boron (B) corresponding to No. 2. FIG. 7 is a graph showing the dependence of the electron density shown in Table 2 on the composition ratio of boron (B).

[0060]

[Table 2] As shown in Table 2, FIG. 6 and FIG. 7, Ga _{1 in which the} amount of boron (B) is constant, ie, the composition ratio of boron (B) is about 5 to 10 mol%, compared to the case where boron (B) is not added. _{-x In} B _x N, (x
= 0.05 to 0.1), the electron mobility, the full width at half maximum (FWHM) and the electron concentration characteristics of the GaN crystal layer are improved. Further, when the composition ratio of boron (B) is increased to about 5 to 10 mol% or more, the above characteristics are found to be deteriorated.

As the substrate on which the buffer layer is grown, a silicon carbide (SiC) substrate can be used instead of the sapphire substrate 11. Since the silicon carbide (SiC) substrate itself is made of a semiconductor material, when an operating voltage is applied, current can be conducted and the nitride-based compound semiconductor device of the present invention is applied to a semiconductor light emitting device. In this case, it can be usefully used. However, silicon carbide (S
iC) When a nitride-based single crystal is formed thereon similarly to the sapphire substrate 11, stress is generated at the interface due to lattice mismatch, so a buffer layer is required.

The buffer layer of the present invention can be made of other compound semiconductors in addition to Ga _1-x B _x N. As shown in FIG. 8, since BN itself has a small lattice constant difference from the sapphire substrate, compound semiconductors used as conventional buffer layers, that is, AlN, GaN, and InN and BN are used.
Compound semiconductors such as ternary systems composed of mixed crystals of
It is a good buffer layer capable of improving the crystallinity of a single crystal layer epitaxially grown on a sapphire substrate.

That is, Ga _1−x B _x N (0 <x ≦ 1), Al
_1-x B _x N (0 <x ≦ 1), In _1-x B _x N (0 <x ≦
_{1), ((Al 1-} y Ga y) 1-x B x) N (0 <x ≦ 1,0
≦ y ≦ 1), ((In _1−y G _ay ) _1−x B _x ) N (0 <x ≦
1,0 ≦ y ≦ 1), ( (Al a Ga b In c) 1-x B x) N
(0 <x <1, a + b + c = 1, where A, B, and C are not 0), and the like. Can be used as a layer.

The buffer layer of the present invention comprises the above ternary system,
It may be grown at a first substrate temperature T _SUB1 using a reaction gas (raw material gas) containing a quaternary or quinary or higher BN compound semiconductor component element (constituent element).
For example, first, about 200 to 1000 ° C., preferably about 5
At a first substrate temperature T _SUB1 of 00 to 600 ° C., 1
It grows to a thickness of １００100 nm, preferably about 10-60 nm, more preferably about 20-30 nm.

Then, the first layer is placed on the buffer layer.
In higher than the substrate temperature T _SUB1 second substrate temperature T _SUB2,
What is necessary is just to epitaxially grow the nitride-based compound semiconductor single crystal layer. The nitride-based compound semiconductor single crystal layer can be epitaxially grown with any material made of a nitride-based compound semiconductor. That is, InN, GaN, AlN, In
_All nitride-based compound semiconductors such as _1-x Ga _x N, Al _1-x Ga _x N, and AlIn _1-x Ga _x N can be epitaxially grown. A nitride-based compound semiconductor single crystal layer made of the above material is epitaxially grown at a second substrate temperature T _SUB2 of about 1100 ° C. or higher, which is higher than the first substrate temperature T _SUB1 . The buffer layer is grown at the first substrate temperature T _SUB1 , and then the reaction gas is supplied to the reaction vessel while gradually increasing to the second substrate temperature T _SUB2 , thereby forming the nitride-based compound semiconductor single crystal layer. .

B between the substrate and the nitride-based compound semiconductor crystal layer
The nitride-based compound semiconductor device on which the buffer layer made of the N-based compound semiconductor is formed operates well as a blue LED. Embodiments of the present invention will be described with reference to structural examples (structural examples 1 to 4) of such an LED shown in FIGS.

(Structural Example 1) First, as shown in FIG.
The LED according to Structural Example 1 of the present invention includes a sapphire substrate 11
A BN-based compound buffer layer 24 is formed thereon,
An n-type nitride-based single crystal layer (hereinafter referred to as “n-type nitride-based crystal layer”) 34 is formed thereon.

The BN-based compound buffer layer 24 is composed of a mixed crystal of BN and a compound semiconductor composed of AlN, GaN, and InN.
_{That, Ga 1-x B x N} , Al 1-x B x N, In 1-x B x N, A
_{l 1- y Ga y) 1-} x B x N, ((In 1-y Ga y) 1-x B x)
_{N, ((Al a Ga b} In c) 1 -x B x) an N-like, first substrate temperature T _SUB1 about 200 to 1100 ° C., preferably from about 1 at a substrate temperature T _SUB1 of 500 to 600 ° C. 10
It is epitaxially grown to a thickness of 0 nm, preferably about 10 to 60 nm, more preferably 20 to 30 nm. At the first substrate temperature T _SUB1 , the buffer layer 24 has an amorphous structure, a polycrystalline structure having small crystal grain boundaries, or a mixed structure of an amorphous structure and a polycrystalline structure.

The n-type nitride-based crystal layer 34 has a single crystal structure, and has a first substrate temperature T on the BN-based compound buffer layer 24.
_{At a} second substrate temperature T _SUB2 of about 1000 ° C. or higher, which is higher than _SUB1 , GaN, AlN, In _1-x Ga _x N, Al _1-x G
It is formed by doping an n-type impurity element when epitaxially growing a nitride-based compound semiconductor layer such as a _x N, AlIn _1-x Ga _x N or the like. Alternatively, after epitaxially growing a nitride-based compound semiconductor layer,
It can also be formed by doping an n-type impurity element. The doping of the n-type impurity element is performed using a general doping method with an impurity element such as C, Si, Ge, Se, S, Sn, Te, Be, and O.

An active layer 35 made of a nitride-based compound semiconductor single crystal is formed on n-type nitride-based crystal layer 34. The active layer 35 is made of GaN, AlN, In _1-x Ga _x N, Al _1-x Ga _x which is not intentionally doped with impurities.
It is formed by epitaxially growing an intrinsic semiconductor such as N, AlIn _1-x Ga _x N. The active layer 35 is L
When a predetermined operating voltage is applied to the ED, it constitutes a part of a light emitting region that emits light by transition development of injected carriers.

The active layers 35 have different energy gaps.
May be formed from a plurality of different layers. like this
Layers are for forming a quantum well (QW).
Therefore, it can be formed in two layers, and can be formed in three or more layers.
Rukoto can. Forming a quantum well (QW) in the active layer 35
In order to achieve this, the nitride-based compound
Make the composition ratio of multiple layers of conductor layers different from each other
What is necessary is just to configure. For example, Al_1-xGa_xEpitaxy N
When the active layer 35 is formed by char growth, Al and Ga
To form a plurality of layers having different composition ratios, that is, x values.
Therefore, a quantum well (QW) can be formed. this
In such a quantum well (QW), the quantum well (QW)
Carriers are trapped at a low energy level. This
Transition between bands when operating voltage is applied
The luminous efficiency is greatly increased. Furthermore, quantum well (QW)
The active layer 35 having
Can be realized by forming multiple layers
You. For example, In_1-xGa_xN / GaN, In_1-xGa_x
N / In_1-yGa_yN, In_1-xGa_xN / Al_1-zGa _zN
(Where x ≦ y, 0 ≦ x, y, z ≦ 1)
Active layer also having a quantum well (QW)
35 can be used.

In this case, one layer, for example, a specific layer such as a GaN layer can be formed, and further, a plurality of In _1-x Ga _x N layers can be formed while changing the x value. In this case, the energy level of the GaN layer acts as a potential barrier, and the plurality of In _1-x Ga _x N are formed by a multiple quantum well (MQ).
W). As a result, most carriers are trapped in this multiple quantum well (MQW). By forming at least one of a plurality of layers constituting a multiple quantum well (MQW) by a mixed crystal of compound semiconductors having different energy gaps, a potential having a different energy level depending on a composition ratio of the mixed crystal. Can be formed.

On the active layer 35, a p-type nitride single crystal layer
(Hereinafter referred to as “p-type nitride-based crystal layer”) 36
Is formed. This p-type nitride-based crystal layer 36 is an n-type nitride
GaN, AlN, In_1-xGa_x
N, Al_1-xGa_xN, AlIn _1-xGa_xNitrogen such as N
Of a compound semiconductor on the active layer 35
The p-type impurity element
Is performed. Mg, Zn, C as the p-type impurity element
d, Be, Ca, Sr, Ba and the like are used.

The laminated structure including the n-type nitride-based crystal layer 34, the active layer 35, and the p-type nitride-based crystal layer 36 has a p-type structure in which carriers are injected and activated by applying an operating voltage to both ends. An n-junction structure is formed. Then, the pn junction structure becomes a light emitting region that emits actual light.

As shown in FIG. 2, the laminated structure including the n-type nitride-based crystal layer 34, the active layer 35, and the p-type nitride-based crystal layer 36 partially includes an n-type nitride-based crystal layer. There is provided a concave portion from which 34 is exposed. At the bottom of the recess, a part of the n-type nitride-based crystal layer 34 is further removed. A first electrode (n-electrode) 42 made of a metal having good conductivity is formed at the bottom of the recess.
Further, a second electrode (p-electrode) 41 made of metal is also formed on the p-type nitride-based crystal layer 36. An operating voltage is applied to the pn junction structure through the n-electrode 42 and the p-electrode 41, and carriers are injected beyond the potential barrier at the pn junction interface, so that light is emitted from the light emitting region. start.

Generally, the sapphire substrate 11 is an insulator. Therefore, in order to apply an operating voltage to the active layer 35, in the LED according to the first structural example of the present invention, a part of one side of the n-type nitride-based crystal layer 34 is removed and the n-electrode 4 is placed thereon.
2 are formed. In the LED having such a structure,
When a predetermined voltage is applied between the n-electrode 42 and the p-electrode 4, the p-type nitride-based crystal layer 3
A current flows between the active layer 6 and the n-type nitride-based crystal layer 34, so that light is emitted from the active layer 35.

The n-electrode 42 and the p-electrode 41 are made of a metal having good conductivity, and their types generally differ depending on the n-type nitride-based crystal layer 34 and the p-type nitride-based crystal that are in contact with the electrodes. The method for forming the n-electrode 42 and the p-electrode 41 is as follows.
A general metal deposition method, for example, a vacuum evaporation method or a sputtering method can be used.

(Structure Example 2) The structure of the LED according to Structure Example 2 of the present invention shown in FIG. 3 is basically the same as the LED shown in FIG. However, LE as shown in FIG.
The position of the first electrode (n-electrode) 42a, 42b is different from the structure of D. The reason for employing the structure of the LED as shown in FIG. 3 is that the sapphire substrate 11 is an insulator. Therefore, the n− of the LED shown in FIGS.
Electrodes 42, 42a, 42b and second electrode (p-electrode) 4
1 are all formed on the n-type nitride-based crystal layer 34 and the p-type nitride-based crystal layer 36 so as to be in direct ohmic contact. In particular, when an operating voltage is applied, a current flows through the entire region of the active layer 35, so that the n-type nitride-based crystal layer 34, the active layer 35, and the p-type nitride-based crystal layer 3
A concave portion is formed by removing a part of both sides of the laminated structure made of 6, and n-electrodes 42a and 42b are formed in the n-type nitride-based crystal layer 34 at the bottom of the concave portion. n-electrode 42a,
Reference numeral 42b may be formed as a plurality of independent regions, and is integrally formed as a ring surrounding a convex portion of a laminated structure including the n-type nitride-based crystal layer 34, the active layer 35, and the p-type nitride-based crystal layer 36 at the center. May be formed. That is, although two cross sections 42a and 42b are apparently shown in the cross sectional view shown in FIG. 3, they may be actually configured as continuous electrodes.

(Structure Example 3) The structure of the LED according to Structure Example 3 of the present invention shown in FIG. 4 is basically the same as the LED shown in FIG. However, the positions of the first electrode (n-electrode) 42 and the second electrodes (p-electrodes) 41a and 41b are different from the structure of the LED as shown in FIG. That is, the n-type nitride-based crystal layer 34 and the active layer (35a,
35b) and a portion near the center of the stacked structure composed of the p-type nitride-based crystal layers (36a, 36b) is removed to form a recess, and the n-electrode 42 is formed on the n-type nitride-based crystal layer 34 at the bottom of the recess. Are formed. Due to the central recess, the LED according to Structural Example 3 of the present invention apparently has two active layers 35a and 35b and two p-type nitride-based crystal layers 36a and 36b.
Appears on the cross section. However, these active layers 35
a, 35b and p-type nitride-based crystal layers 36a, 36b
It may be formed as a laminated structure integral with a ring shape surrounding the central recess. Therefore, the p-type nitride-based crystal layer 36a,
The p-electrodes 41a and 41b connected so as to make ohmic contact with the 36b are also apparently two cross sections 41a and 41b in the cross-sectional view of FIG. 4, but are actually configured as a continuous single ring-shaped electrode. You may.

The reason for adopting the structure of the LED as shown in FIG. 4 is that the sapphire substrate 11 is an insulator as described above. Accordingly, the n-electrodes 42, 42a, 42b and the p-electrodes 41, 41a, 41b of the LED as shown in FIGS. 2 to 4 are all n-type nitride-based crystal layers 34 and p-type nitride-based crystals, respectively. It is formed so as to make direct ohmic contact on the layer 36.

According to the structural example 3 of the present invention shown in FIG.
When an operating voltage is applied between the n-electrode 42 and the p-electrodes 41a and 41b, a current flows almost uniformly in the entire region of the active layer (35a and 35b).

(Structure Example 4) FIG. 5 shows a structure example 4 of the present invention.
1 shows the structure of the LED according to the first embodiment. L according to Structure Example 4 of the present invention
The ED is an LED using a silicon carbide (SiC) substrate having a low specific resistance. Since SiC is a semiconductor, the specific resistance can be adjusted by doping impurities. Therefore,
An impurity is doped so as to have a sufficiently high impurity density to form a low-resistivity substrate 12, and electrodes 51 and 52 (the first electrode 51 and the second electrode 5) are interposed via the low-resistivity substrate 12.
An operating voltage can be applied during 2). First electrode 51 and second electrode 51
When an operating voltage is applied between the electrodes 52, a current flows between the first electrode 51 and the second electrode 52 with low resistance. Therefore, as shown in FIG. 5, in the LED according to Structural Example 4 of the present invention, the first electrode 51 can be formed on the lower surface of the SiC substrate 12.

FIG. 5 shows an LED according to structural example 4 of the present invention.
The advantage of this structure is that the area of the light emitting region of the LED can be formed to be the same as the area of the SiC substrate 12. When an operating voltage is applied between the first electrode 51 and the second electrode 52, the current flows uniformly throughout the nitride single crystal layer 35 serving as a light emitting region, so that the light emitting efficiency is greatly improved. .

2 to 4 on a silicon carbide (SiC) substrate.
The same buffer layer 25 as that of the LED shown in FIG. 1 is formed, and a nitride-based single crystal layer 37 is formed thereon. Although the detailed structure of the nitride-based single crystal layer 37 is not shown, a p-type nitride-based single crystal layer, an intrinsic nitride-based single crystal layer (active layer), and an n-type nitride-based single crystal layer It is a multilayer structure consisting of The buffer layer 25 is a non-single-crystal layer made of a BN-based compound semiconductor. Buffer layer 25 improves the crystallinity of the nitride-based single crystal layer by preventing lattice mismatch from occurring between silicon carbide (SiC) substrate 12 and nitride-based single crystal layer 37.

In the nitride-based single crystal layer 37, if the p-type nitride-based single crystal layer is below and the n-type nitride-based single crystal layer is above,
The electrode (first electrode) 51 is a p-electrode, an electrode (second electrode)
52 is an n-electrode. Conversely, if the p-type nitride-based single crystal layer is upper and the n-type nitride-based single crystal layer is lower, the first electrode 51
It goes without saying that the n-electrode and the second electrode 52 are p-electrodes. However, which is the first electrode and which is the second electrode
Calling them electrodes is only a matter of how they are called.

(Other Embodiments) As described above, the present invention has been specifically described using Structural Examples 1 to 4. However, the description and drawings constituting a part of this disclosure limit the present invention. Should not be understood to be. From this disclosure, various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art.

The nitride-based compound semiconductor device of the present invention can be applied to a general semiconductor light-emitting device made of a nitride-based compound semiconductor. A pn junction structure made of a nitride-based compound semiconductor is formed on substrates having different lattice constants, such as a semiconductor laser, a light-emitting transistor, and an optical integrated circuit, as well as the LED described in the above structure examples 1 to 4. All of the manufactured semiconductor devices can easily produce more efficient semiconductor devices by utilizing the concept of the present invention.

Further, the method for growing a crystal of a nitride-based compound semiconductor of the present invention is not limited to a specific semiconductor device. The present invention relates to a method for epitaxially growing a nitride-based compound semiconductor (second solid material) on a substrate made of a material (first solid material) having a different lattice constant, and only to a crystal growth method for a specific semiconductor device. It is not limited.

As described above, the present invention naturally includes various embodiments and the like not described herein. Therefore, the technical scope of the present invention is determined only by the invention specifying matters according to the claims that are appropriate from the above description.

[0090]

As described above, according to the present invention, the BN compound buffer layer is formed on a substrate made of a material (first solid material) having a different lattice constant, such as a sapphire substrate or a silicon carbide (SiC) substrate. Therefore, when a nitride-based compound semiconductor single crystal layer (second solid material) is epitaxially grown,
Mitigates lattice mismatch between the substrate and the nitride buffer layer,
The crystallinity of the nitride-based compound semiconductor single crystal layer (second solid material) can be improved.

Further, according to the present invention, when a semiconductor light emitting device such as an LED is manufactured by improving the crystallinity, the light emitting characteristics and the electric characteristics are improved.

Further, according to the present invention, since the crystallinity of the nitride-based compound semiconductor single crystal layer is improved, the reliability and the operating life are greatly increased.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a nitride-based compound semiconductor device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a structure of a blue LED according to a structural example (structural example 1) of an embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of a blue LED according to a structural example (structural example 2) of the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a structure of a blue LED according to a structural example (structural example 3) of the embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a structure of a blue LED according to a structural example (structural example 4) of the embodiment of the present invention.

FIG. 6 is a graph showing characteristics of the nitride-based compound semiconductor crystal layer according to the embodiment of the present invention.

FIG. 7 is a graph showing characteristics of the nitride-based compound semiconductor crystal layer according to the embodiment of the present invention.

FIG. 8 is a graph showing a relationship between lattice constants and energy gaps of various nitride-based compound semiconductors and sapphire.

FIG. 9 is a sectional view showing the structure of a conventional nitride-based compound semiconductor device.

[Explanation of symbols]

11 sapphire substrate 21 GaAlN buffer layer 22 GaN buffer layer 23 GaBN buffer layer 24 BN compound buffer layer 31,32 Ga _x Al _1-x N crystal layer 33 GaN crystal 34 n-type nitride-based crystal layer 35, 35a, 35b activity Layers 36, 36a, 36b P-type nitride-based crystal layer 37 Nitride-based single crystal layer 41, 41a, 41b P-electrode 42, 42a, 42b N-electrode 51, 52 Electrode

Claims (55)

[Claims] 1. A nitride compound semiconductor device comprising at least a substrate, a buffer layer composed of a BN compound semiconductor disposed on the substrate, and a nitride compound semiconductor crystal layer disposed on the buffer layer. . 2. The nitride-based compound semiconductor device according to claim 1, wherein said buffer layer is a semiconductor layer having a structure in which atomic arrangement is disordered. 3. The nitride-based compound semiconductor device according to claim 2, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is an amorphous layer. 4. The nitride-based compound semiconductor device according to claim 2, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is a polycrystalline layer. 5. The nitride-based compound according to claim 2, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is a layer in which an amorphous state and a polycrystalline state are mixed. Semiconductor element. 6. The nitride-based compound semiconductor device according to claim 1, wherein said substrate is a sapphire substrate or a silicon carbide (SiC) substrate. 7. The buffer layer has a thickness of 10 to 60 n.
2. The nitride-based compound semiconductor device according to claim 1, wherein m is m. 8. The buffer layer has a thickness of 20 to 30 n.
8. The nitride-based compound semiconductor device according to claim 7, wherein m is m. 9. The method according to claim 1, wherein the BN-based compound semiconductor is AlN, G
2. The nitride-based compound semiconductor device according to claim 1, wherein the nitride-based compound semiconductor device is a mixed crystal comprising at least one compound semiconductor selected from a group consisting of aN and InN and BN. 10. The semiconductor device according to claim 1, wherein the BN-based compound semiconductor is Ga _1-x
10. A device according to claim 9, wherein B _x N (0 <x ≦ 1).
3. The nitride-based compound semiconductor device according to item 1. 11. The method according to claim 11, wherein the BN-based compound semiconductor is Al _1-x
10. A device according to claim 9, wherein B _x N (0 <x ≦ 1).
3. The nitride-based compound semiconductor device according to item 1. 12. The method of claim 1, wherein the BN-based compound semiconductor is In _1-x
10. A device according to claim 9, wherein B _x N (0 <x ≦ 1).
3. The nitride-based compound semiconductor device according to item 1. 13. The method according to claim 1, wherein the BN-based compound semiconductor comprises ((Al
_{1-y Ga y) 1-} x B x) N (0 <x ≦ 1,0 ≦ y ≦ 1) nitride compound semiconductor device according to claim 9, characterized in that a. 14. The method according to claim 14, wherein the BN-based compound semiconductor is ((In
_{1-y Ga y) 1-} x B x) N (0 <x ≦ 1,0 ≦ y ≦ 1) nitride compound semiconductor device according to claim 9, characterized in that a. 15. The method according to claim 15, wherein the BN-based compound semiconductor is ((In
_{1-y Al y) 1-} x B x) N (0 <x ≦ 1,0 ≦ y ≦ 1) nitride compound semiconductor device according to claim 9, characterized in that a. 16. The method according to claim 16, wherein the BN-based compound semiconductor is ((Al _{a
Ga b In c) 1-x} B x) N (0 <x ≦ 1, a + b + c =
10. The nitride-based compound semiconductor device according to claim 9, wherein 1, a, b, c ≠ 0. 17. The nitride-based compound semiconductor crystal layer,
2. The nitride-based compound semiconductor device according to claim 1, wherein the device is made of at least one compound semiconductor of a group consisting of AlN, GaN, and InN. 18. A step of preparing a substrate, a step of growing a BN-based compound semiconductor layer on the substrate at a first substrate temperature to form a buffer layer, and a second substrate temperature higher than the first substrate temperature. , A step of epitaxially growing a nitride-based compound semiconductor crystal layer on the buffer layer. 19. The temperature of the first substrate is 200 to 1000.
The method for growing a nitride-based compound semiconductor according to claim 18, wherein the temperature is ℃. 20. The temperature of the first substrate is 500 to 600 ° C.
20. The method of growing a nitride-based compound semiconductor according to claim 19, wherein: 21. The method according to claim 18, wherein the temperature of the second substrate is 1000 ° C. or higher. 22. The nitride-based compound semiconductor crystal layer is
19. The nitride-based compound semiconductor device according to claim 18, comprising at least one compound semiconductor of a group consisting of 1N, GaN, and InN. 23. A first layer made of a first solid material, a second layer made of a second solid material having a nitride-based compound semiconductor crystal structure having a lattice constant different from that of the first solid material, and the first layer And a buffer layer made of a BN-based compound semiconductor that lattice-matches the first layer and the second layer arranged between the second layer and the second layer. 24. The nitride-based compound semiconductor device according to claim 23, wherein the buffer layer is a semiconductor layer having a structure in which the regularity of atomic arrangement is disordered. 25. The semiconductor layer according to claim 2, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is an amorphous layer.
5. The nitride-based compound semiconductor device according to 4. 26. The semiconductor layer according to claim 2, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is a polycrystalline layer.
5. The nitride-based compound semiconductor device according to 4. 27. The nitride compound according to claim 24, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is a layer in which an amorphous state and a polycrystalline state are mixed. Semiconductor element. 28. A substrate, a buffer layer formed of a BN-based compound semiconductor disposed on the substrate, an n-type nitride-based compound semiconductor crystal layer disposed on the buffer layer, and the n-type nitride-based An active layer formed of a nitride-based compound semiconductor crystal disposed on the compound semiconductor crystal layer; a p-type nitride-based compound semiconductor crystal layer disposed on the active layer; and a voltage generator for applying a voltage to the active layer. A nitride-based compound semiconductor device comprising a first electrode and a second electrode. 29. The nitride-based compound semiconductor device according to claim 28, wherein the buffer layer is a semiconductor layer having a structure in which the atomic arrangement is disordered. 30. The semiconductor layer having a structure in which the regularity of the atomic arrangement is disordered is an amorphous layer.
10. The nitride-based compound semiconductor device according to item 9. 31. The semiconductor layer having a structure in which the regularity of the atomic arrangement is disordered is a polycrystalline layer.
10. The nitride-based compound semiconductor device according to item 9. 32. The nitride-based compound semiconductor according to claim 29, wherein the semiconductor layer having a structure in which the atomic arrangement is disordered is a layer in which an amorphous state and a polycrystalline state are mixed. element. 33. The buffer layer has a thickness of 10 to 60.
29. The nitride-based compound semiconductor device according to claim 28, wherein 34. The buffer layer has a thickness of 20 to 30.
34. The nitride-based compound semiconductor device according to claim 33, wherein 35. The BN-based compound semiconductor comprises AlN,
The nitride-based compound semiconductor device according to claim 28, comprising a mixed crystal of at least one compound semiconductor selected from a group consisting of GaN and InN and BN. 36. The nitride-based compound semiconductor crystal layer is made of A
29. The nitride-based compound semiconductor device according to claim 28, comprising at least one compound semiconductor of a group consisting of 1N, GaN, and InN. 37. The method according to claim 37, wherein the nitride-based compound semiconductor crystal layer is made of A
29. The nitride-based compound semiconductor device according to claim 28, comprising a mixed crystal of at least two compound semiconductors of a group consisting of 1N, GaN, and InN. 38. The nitride-based compound semiconductor device according to claim 28, wherein said active layer includes at least one quantum well. 39. The quantum well includes a plurality of nitride compound semiconductor crystal layers having different composition ratios of constituent elements inside the nitride compound semiconductor crystal layer of the active layer. 39. The nitride-based compound semiconductor device according to claim 38. 40. The active layer comprises: a first layer forming an energy barrier; and a composition ratio of constituent elements different from that of the first layer to form the quantum well, and a forbidden band with the first layer. 39. The nitride-based compound semiconductor device according to claim 38, further comprising a second layer having different energy. 41. The active layer comprises: a first layer forming an energy barrier; and a composition ratio of constituent elements different from that of the first layer to form a predetermined potential profile, forbidden from the first layer. 39. The nitride-based compound semiconductor device according to claim 38, further comprising: a second layer having a different band energy. 42. The nitride-based compound semiconductor device according to claim 28, wherein said substrate is a sapphire substrate. 43. The semiconductor device according to claim 43, wherein the first electrode is disposed on the n-type nitride-based compound semiconductor crystal layer, and the second electrode is disposed on the p-type nitride-based compound semiconductor crystal layer. 43. The nitride-based compound semiconductor device according to claim 42. 44. The nitride-based compound semiconductor device according to claim 28, wherein said substrate is a silicon carbide (SiC) substrate. 45. The device according to claim 45, wherein the first electrode is disposed on a surface opposite to a surface of the substrate that is in contact with the buffer layer,
The nitride-based compound semiconductor device according to claim 44, wherein an electrode is disposed on the p-type nitride-based compound semiconductor crystal layer. 46. A step of preparing a substrate, a step of forming a buffer layer by epitaxially growing a BN-based compound semiconductor layer on the substrate at a first substrate temperature, and a step of forming a buffer layer on the substrate at a second substrate temperature higher than the first substrate temperature. Forming an n-type nitride-based compound semiconductor crystal layer on the buffer layer; growing an nitride-based compound semiconductor crystal on the n-type nitride-based compound semiconductor crystal to form an active layer; Forming a p-type nitride-based compound semiconductor crystal layer on the active layer; and forming a first electrode and a second electrode for applying a voltage to the active layer. Production method. 47. The temperature of the first substrate is 200 to 1000.
The method for manufacturing a nitride-based compound semiconductor device according to claim 46, wherein the temperature is ° C. 48. The temperature of the first substrate is 500 to 600 ° C.
The method for manufacturing a nitride-based compound semiconductor device according to claim 47, wherein: 49. The method according to claim 46, wherein the temperature of the second substrate is 1000 ° C. or higher. 50. The method according to claim 50, wherein the nitride-based compound semiconductor crystal layer
47. A semiconductor device comprising at least one material selected from the group consisting of 1N, GaN, and InN compound semiconductors.
3. The method for producing a nitride-based compound semiconductor device according to item 1. 51. The method of forming an n-type nitride-based compound semiconductor crystal layer, wherein the nitride-based compound semiconductor includes C, S
47. The method according to claim 46, further comprising a step of doping at least one impurity element selected from the group consisting of i, Ge, Se, S, Sn, Te, and Be. . 52. The method of forming a p-type nitride-based compound semiconductor crystal layer according to claim 52, wherein the nitride-based compound semiconductor includes Mg, Z
The method for manufacturing a nitride-based compound semiconductor device according to claim 46, further comprising a step of doping at least one impurity element selected from the group consisting of n, Cd, Be, Ca, Sr, and Ba. 53. A laminated body having a pn junction structure composed of a BN-based compound semiconductor disposed on a substrate, a BN-based compound semiconductor disposed on the buffer layer, and the pn A nitride-based compound semiconductor device comprising a first electrode and a second electrode for applying a voltage to a laminate having a junction structure. 54. A step of epitaxially growing a BN-based compound semiconductor layer on a substrate at a first substrate temperature to form a buffer layer; Composed of compound semiconductors
forming a stacked body having an n-junction structure; and forming a first electrode and a second electrode for applying a voltage to the stacked body having a pn junction structure. A method for manufacturing a compound semiconductor device. 55. A buffer layer formed of a BN-based compound semiconductor disposed on a substrate, a nitride-based compound semiconductor crystal layer disposed on the buffer layer and forming a light-emitting region, and applying a voltage to the light-emitting region. The first electrode and the second
A nitride-based compound semiconductor device comprising an electrode.