JPH11346001A - Iii group nitride semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make feasible of sufficiently exercising the effect by adopting a cubic structure crystal Si substrate in III group nitride semiconductor light emitting element. SOLUTION: In this III group nitride semiconductor light emitting element 10 composed of a laminated light emitting part 3 comprising III group nitride semiconductor through the intermediary of a buffer layer 2 on a conductive silicon single crystal substrate 1, the buffer layer 2 is formed of a BP based III group element-V group compound semiconductor crystal 21 in the composition ratio of 1 to 1 as a main body crystal as well as multiatom boron phosphide crystal (BXPY:X>=6, 0<Y<=2) 22 in the composition ratio of boron element and phosphorus element exceeding 6 to 1 as a subordinate crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a group III nitride semiconductor light emitting device in which a light emitting part made of a group III nitride semiconductor is laminated on a conductive silicon single crystal substrate via a buffer layer. .

[0002]

2. Description of the Related Art Structural formulas Al _A Ga _B In _C Q _{1 -Z} N _Z (0 ≦
A, B, C ≦ 1, A + B + C = 1, 0 <Z ≦ 1, symbol Q
Represents a V element other than nitrogen. The group III nitride semiconductor crystal represented by) has a forbidden band width suitable for emitting short-wavelength light in the near-ultraviolet band and the blue to green band (Yasuharu Suematsu, “Optical Devices”). (Refer to the first edition, 8th printing on May 15, 1997, published by Corona Co., Ltd.), pp. 28-29). For this reason, light emitting diodes (LE
D) and a light emitting unit of a laser diode (LD) (Mat. Res. Soc. Symp. Pro).
c. Vol. 449 (1997), pp. 509-518). The light-emitting portion of these light-emitting elements is usually formed of a pn-junction type double hetero (DH) junction structure advantageous for obtaining high light-emission output (Iwao Teramoto, "Introduction to Semiconductor Devices" ( First edition on March 30, 1995,
(Published by Baifukan Co., Ltd.), pages 124-125).

[0003] Many conventional light emitting devices made of Group III nitride semiconductors use hexagonal sapphire (α-Al ₂ O ₃ single crystal) as a substrate material (Jpn. J. Appl. P).
hys. , 34 (1995), L1332-L1335
Page). In addition, a buffer layer is generally provided on the sapphire substrate for the purpose of relieving a lattice mismatch (mis-match) with the group III nitride semiconductor crystal layer to be laminated (Japanese Patent Laid-Open No. 2-229476). And Japanese Patent Application Laid-Open No. 4-297,023).
The buffer layer is usually made of aluminum gallium nitride (Al _A G
a _B N: 0 ≦ A, B ≦ 1, A + B = 1)
In addition, a film is formed at a relatively low temperature of about 400 ° C. to about 900 ° C. (Edited by Isamu Akasaki, “III-V Group Compound Semiconductor” (19
First edition, May 20, 1994, published by Baifukan Co., Ltd.), 335-
337).

[0004] However, when the light emitting element is formed by using sapphire for the substrate as described above, the following problems occur. First, since sapphire is an electrical insulator, both n-type and p-type ohmic electrodes necessary for forming a light-emitting element are provided on the same side, and one of the electrodes is used for a light-emitting portion. That is, it is necessary to remove and provide a part. The removal of a part of the light emitting portion results in a remarkable decrease in the surface area of a region that emits light (that is, a pn junction region), which is disadvantageous for obtaining a light emitting element with high light emission intensity (see Jpn. Appl.Phys., 34.
(1995), FIG. 1).

Another problem is that sapphire belonging to the hexagonal system does not exhibit clear cleavage. The lack of the cleavage property inhibits the formation of an optical resonance surface that promotes laser light resonance and requires smoothness and flatness in an LD, for example.

Further, a hexagonal group III nitride semiconductor crystal layer is naturally formed on a hexagonal substrate, and the hexagonal group III nitride semiconductor crystal layer is formed as compared with a cubic crystal. It is difficult to obtain a p-type conductive layer. This is because a cubic crystal such as a zinc-blend type and a wurtzite-type hexagonal crystal have a difference in the band gap of the valence band in the valence band ( See Tokaki Ikoma and Hideaki Ikoma, "Introduction to Basic Properties of Compound Semiconductors" (published by Baifukan Co., Ltd., p. 17). That is, in the case of the wurtzite-type hexagonal crystal, the confinement band of the hole band of the valence band is released, and as a result, it becomes difficult to release holes, and thus it is difficult to obtain a p-type conductive layer. On the other hand, in the cubic crystal, since the constriction of the hole band of the valence band is not released, the holes are easily released and the p-type conductive layer with low resistance is easily formed.

[0007] The above-mentioned various problems that occur when a group III nitride semiconductor light-emitting device is formed using hexagonal sapphire as a substrate are expected to be solved by using a cubic single crystal as a substrate. Is done. For example, as a cubic single crystal, diamond crystal structure type silicon (Si),
Gallium arsenide (GaAs) or gallium phosphide (GaP)
And the like. A zinc-blende type III-V compound semiconductor crystal is used as a substrate.

When such a cubic single crystal is used as a substrate, first, since a conductive substrate can be used, the problem of a reduction in the light emitting area associated with the conventional arrangement of ohmic electrodes is solved. . Further, since these diamond structure type and zinc blende type single crystals exhibit a clear cleavage in the [011] crystal direction, it is possible to easily form an optical resonance surface in the LD. Furthermore, since it is a cubic crystal, a low-resistance p-type conductive layer can be easily formed.

For this reason, recently, conductive silicon (S
i) A technique for forming a group III nitride semiconductor light emitting device using a single crystal as a substrate has been known (Elect).
ron. Lett. Vol. 33, no. 23 (19
97), 1986-1987). An example is disclosed in which a thin layer made of aluminum nitride (AlN) is provided as a buffer layer between the silicon substrate and the group III nitride semiconductor crystal layer (Appl. Phys. Le).
tt. , 72 (4) (1998), 415-417).

According to this example, the AlN crystal layer provided on the silicon substrate is hexagonal. Also, this A
On the 1N crystal layer, a pn junction type DH structure light emitting portion including GaN as a light emitting layer is provided, and the light emitting portion is formed of a hexagonal group III nitride semiconductor crystal layer. I have. In other words, the light emitting portion is still composed of a hexagonal crystal layer, as in the case of a conventional group III nitride light emitting device using sapphire as a substrate, and the effect of using a silicon substrate is sufficiently utilized. It has not been fully demonstrated.

In addition, a method using silicon (Si) as a substrate III
In another conventional example of a group III nitride semiconductor light emitting device, a configuration in which a zinc blende-type cubic boron phosphide (BP) layer is used as a buffer layer is disclosed (see Japanese Patent Application Laid-Open No. 2-275682). .

[0012]

However, while the lattice constant of BP forming the buffer layer is 4.538 °,
That of Si forming the substrate is 5.431 °, which is greatly different. Therefore, the above-mentioned Japanese Patent Laid-Open No.
Even if an attempt is made to form a BP crystal layer on the surface of a Si substrate by a conventional method of growing a buffer layer, as in the conventional example disclosed in 275682, the BP-based crystal is actually formed on the surface of the Si substrate. Growing islands are only scattered (Naoya Shibusawa, Kazutaka Terashima, "Journal of Japan Society for Crystal Growth", Vol.2)
4, no. 2 (1997), p. 150). It is extremely difficult to stack a crystal layer having continuity on such a film having no continuity.

[0013] In addition, a conventional method for growing a buffer
Even if a BP-based crystal can be grown on a substrate, most of it is a hexagonal crystal containing boron as a multi-atom (hereinafter, referred to as “boron polyatomic boron phosphide”) represented by B ₁₃ P _2. "), And it was also found that BP having a cubic structure was generated only slightly. An upper layer inheriting the crystal system of the crystal constituting the buffer layer is formed on the buffer layer mainly composed of such boron-polyatomic boron phosphide. Lamination of cubic crystal layers is difficult.

FIG. 14 is mainly composed of boron polyatomic boron phosphide.
-Ray diffraction spectroscopy of boron phosphide film formed on buffer layer composed of
FIG. Boron phosphide film is deposited on Si substrate
Buffer layer formed mainly of boron polyatomic boron phosphide
It is formed by growing it at 1030 ° C. on it. In the figure
As shown, the boron phosphide film has (111) and (112)
Were observed. Diffraction peak (11
1) is a peak derived from the (004) crystal plane of the Si substrate.
It is. The diffraction peak (112) is₁₃P _TwoNo mi
The Lah index (hkl) is (220), (021), (0
27) or X-ray diffraction from (104) crystal plane
Is the peak attributed to Light from BP binary crystal
No obvious diffraction peak was recognized. Thus, boron
Originally cubic crystal on buffer layer mainly composed of polyatomic boron phosphide
Even if a boron phosphide film having a structure is formed, the boron phosphide
The film is a crystal layer with a very low cubic structure ratio
Was.

As described above, even if an attempt is made to form a BP layer as a buffer layer on a Si substrate, the buffer layer is mainly composed of boron polyatomic boron phosphide such as B ₁₃ P _2. Also in this case, the light emitting portion formed on the buffer layer becomes a hexagonal group III nitride semiconductor crystal layer,
The effect using the cubic Si substrate cannot be sufficiently exhibited.

The present invention has been proposed in view of the above,
It is an object of the present invention to provide a group III nitride semiconductor light emitting device capable of sufficiently exhibiting the effect of using a cubic Si substrate as a substrate.

[0017]

In order to achieve the above-mentioned object, according to the first aspect of the present invention, a light emitting portion made of a group III nitride semiconductor is laminated on a conductive silicon single crystal substrate via a buffer layer. In the III-nitride semiconductor light-emitting device constructed as described above, the buffer layer is mainly composed of a BP-based III-V compound semiconductor crystal having a composition ratio of a III-group element to a V-group element of 1: 1. Boron polyatomic boron phosphide crystal in which the composition ratio of the element and the phosphorus element is 6: 1 or more (B _x P _Y : X ≧
6, 0 <Y ≦ 2) are formed as subordinate crystals.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the buffer layer further comprises:
It is characterized in that it becomes a single crystal at the bonding interface side with the silicon single crystal substrate and becomes amorphous at the upper layer side.

According to a third aspect of the present invention, in addition to the constitution of the first aspect of the present invention, the dependent crystal as a whole
0% or less.

According to a fourth aspect of the present invention, in addition to the configuration of the first aspect of the invention, the main crystal is a boron phosphide crystal (BP).

According to a fifth aspect of the present invention, in addition to the configuration of the first aspect, the main crystal is a boron-gallium phosphide crystal.

Further, the invention according to claim 6 is characterized in that, in addition to the configuration of the invention described in claim 1, the main crystal is a boron-indium phosphide crystal.

According to a seventh aspect of the present invention, in addition to the configuration of the first aspect of the present invention, the buffer layer further comprises:
It is characterized in that buffer layers having different proportions of the main crystals are formed in layers.

Further, the invention according to claim 8 is characterized in that an intervening layer is provided between the buffer layer and the light emitting portion constituting layer in addition to the structure of the invention described in claim 1. And

According to a ninth aspect of the present invention, in addition to the constitution of the eighth aspect, the intervening layer is a composition gradient layer.

According to a tenth aspect of the present invention, in addition to the configuration according to any one of the first to ninth aspects, the buffer layer is a low-temperature buffer grown at a low temperature of 250 ° C. or more and 600 ° C. or less. Layer.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a diagram schematically showing a part of a laminated structure of a group III nitride semiconductor light emitting device of the present invention. Referring to FIG. 1, a group III nitride semiconductor light emitting device 10 of the present invention includes a light emitting unit 3 made of a group III nitride semiconductor on a conductive silicon (Si) single crystal substrate 1 via a buffer layer 2.
Are laminated.

The Si single crystal substrate 1 is a cubic crystal having a diamond structure, and has a clear cleavage in the [011] crystal direction. The buffer layer 2 is laminated on the Si single crystal substrate 1. The conductive semiconductor single crystal material other than Si includes a group III-V compound semiconductor crystal such as gallium arsenide (GaAs) or gallium phosphide (GaP). In some cases, a high temperature exceeding about 1000 ° C. is required for forming a crystal layer. In this embodiment, a Si single crystal is used as a substrate because of its superiority such as heat resistance.

The buffer layer 2 is mainly composed of a cubic boron phosphide (BP) -based III-V compound semiconductor crystal 21 having a composition ratio of boron element to phosphorus element of 6: 1 or more. Polyatomic boron phosphide crystal (B _i P _j : i ≧ 6, 0 <j
≦ 2) 22 as a subordinate crystal. Details of the buffer layer 2 will be described later.

The light emitting section 3 is formed by laminating a crystal layer made of a group III nitride semiconductor on the buffer layer 2. Since the main crystal of the buffer layer 2 is a cubic crystal, each layer of the light emitting section 3 is formed. Are also mainly composed of cubic crystals. Emitting unit 3, for example, n-type cubic _{Al A Ga B N (0 ≦} A, B ≦ 1, A + B =
1) A cubic n-type Ga _C
In _D N (0 ≦ C, D ≦ 1, C + D = 1) is used as a light emitting layer, and a cubic p-type Al _A Ga _B N (0 ≦ A, B ≦
1, A + B = 1) The crystal layer is configured as an upper cladding layer. In this case, the light-emitting layer, the Ga _C In _D N layer may be formed as a quantum well structure and the quantum well layer.

Further, since the light-emitting portion 3 in this embodiment can be formed into a cubic crystal as described above, a low-resistance p-type can be obtained without requiring any special treatment such as heat treatment. The conductive layer can be easily formed.

As described above, the buffer layer 2 is made of a cubic group III-V compound semiconductor crystal containing boron B as a group III element and phosphorus P as a group V element (hereinafter referred to as "BP-based III
21) and a boron polyatomic BP crystal 22 containing a large number of boron elements. BP
The system III-V compound semiconductor crystal 21 can be made of not only BP but also, for example, a multi-element mixed crystal containing gallium Ga or indium In as a group III constituent element. However, in order to easily obtain the buffer layer 2 having stable characteristics, it is desirable that the base material has a configuration that is as simple as possible. It is desirable to use a quaternary mixed crystal rather than a quaternary mixed crystal.

When the main crystal is a ternary mixed crystal, a boron phosphide / gallium mixed crystal (B _X Ga _{1 -X} P: 0 ≦ X ≦ 0.04)
And a mixed crystal of boron phosphide and indium (B _Y In _1-Y P: 0 ≦
Y ≦ 0.66) is particularly suitable for forming the buffer layer 2. This is because a zinc blende type B _0.02 Ga _0.98 P mixed crystal having a boron composition ratio X of 0.02 and a boron composition ratio Y
B _0.33 In _0.67 P mixed crystal having a value of 0.33 has the same lattice constant as 5.431 ° of the lattice constant of Si used as the substrate, and each mixed crystal having a boron composition ratio in the vicinity thereof is almost lattice-matched to Si. It is because

On the other hand, a boron polyatomic BP crystal 22 is represented by the general formula B
Assuming that iPj (i ≠ 0, j ≧ 1), i is 7
The existence of polyatomic crystals from No. 10 to No. 10 is known (Katsufusa Shono, "Semiconductor Technology (1)" (9th edition, June 25, 1992, published by The University of Tokyo Press, p. 76). ). In addition, a typical BiPj crystal includes a crystal represented by a chemical formula B ₁₃ P ₂ where i = 13 and j = 2 (VIMA).
TKOVICH, Acta. Cryst. , 14 (19
61), page 93, and J.I. Amer. Ceramic
Society, 47 (1964), pp. 44-46).

In the present invention, the BP-based III-V compound semiconductor crystal 21 and the boron polyatomic BP crystal 22 are quantitatively defined, and the BP-based III-V compound semiconductor crystal 21 is , More than the boron polyatomic BP crystal 22. That is, the BP III-V compound semiconductor crystal 2
The buffer layer 2 is formed with 1 as a main crystal and a boron polyatomic BP crystal 22 as a subordinate crystal.

As described above, the polyatomic BP crystal is a hexagonal system (Ame), as described in the section of the prior art.
r. Ceramic Society, 47 (196
4), pages 44-46, and American Soc
iety of Testing Materials
When the buffer layer is formed with this hexagonal system, the light emitting portion also becomes hexagonal, and the object of the present invention is to make the light emitting portion cubic using a cubic Si substrate. This is because it cannot be achieved.

Specifically, the amount of the subordinate crystal boron polyatomic BP crystal 22 is set to be less than about 30% of the entire buffer layer 2, and it is particularly preferable to set the amount to 10% or less. If the amount of the dependent crystal is so small, it does not affect the crystal system of the upper layer. In addition, a polyatomic boron BP crystal 22
May not necessarily be an essential component of the buffer layer 2. In the boron polyatomic BP crystal 22, when the number of boron atoms constituting a molecule increases, the volume occupied by the molecule naturally increases, and the strain in the buffer layer 2 increases. Including atoms,
That is, in the structural formula BiPj, a boron polyatomic BP crystal where i ≧ 6 is an object whose amount is regulated. The number j of phosphorus atoms constituting one molecule is usually 1 or 2, and the structural formula of the corresponding boron polyatomic BP crystal includes, for example, B ₆ P, B ₁₂ P ₂ , B ₁₃ P _{2 and the} like. There is.

B ₁₃ P, a typical boron polyatomic BP crystal
It is known that ₂ is produced from BP according to the following reaction formula (1). 52BP → 4B ₁₃ P ₂ + 11P ₄ ... (1) B _{13 due} to the thermal decomposition of BP represented by this reaction formula (1)
The generation of P ₂ progresses more actively as the temperature increases (edited by the Japan Society for Industrial Technology Promotion, New Materials Technology Committee, “Compound Semiconductor Device” (September 15, 1973, issued by the Industrial Research Institute, Inc.), 248 Page). Therefore, in order to suppress the content of the boron polyatomic BP crystal 22 represented by the chemical formula B ₁₃ P ₂ to a small amount and increase the amount of the BP-based III-V compound semiconductor crystal 21, it is necessary to form the buffer layer 2. It is reasonable to keep the temperature low. For example, when forming the buffer layer 2 mainly composed of BP by a halide vapor phase epitaxy (VPE) method using phosphorus trichloride (PCl ₃ ) and boron trichloride (BCl ₃ ) as raw materials, the film forming temperature is reduced to about When the temperature is set in the range of 300 ° C. to about 500 ° C., it is possible to form the buffer layer 2 that satisfies the regulation of the present invention regarding the content of the sub crystal 22. In the case of depositing on the (001) crystal plane of the Si single crystal substrate 1 by the above-described VPE method, a particularly desirable temperature is approximately from 300 ° C. to 400 ° C. In the formation of the buffer layer 2 mainly composed of BP by the metalorganic pyrolysis vapor phase epitaxy (MOVPE) method using diborane (B ₂ H ₆ ) and phosphine (PH ₃ ) as a raw material, a desirable temperature is generally about 250 ° C. C to about 600C. Next, the structure of the buffer layer 2 when the buffer layer 2 is formed at a relatively low temperature will be described with reference to FIG.

FIG. 2 is a diagram schematically showing the structure of the buffer layer. As described above, when the buffer layer 2 formed at a relatively low temperature such that the BP-based III-V compound semiconductor crystal 21 becomes the main crystal, when observing the internal crystal structure, as shown in FIG. A single crystal 2m is arranged on the bonding interface 4 side between the Si single crystal substrate 1 and the buffer layer 2, and an amorphous body 2n is arranged on the single crystal 2m. This single crystal body 2m has a pseudomorphism (pseudomorphism) in a region corresponding to the thickness of several lattices from the junction interface 4.
Inheriting the lattice constant of Si on the substrate 1 side, reflecting the phenomena (see “Thin Film / Surface Phenomena”, edited by Takayoshi Hashiguchi et al., Material Science Course 6, published by Asakura Shoten, pp. 11-12). And plays a role of providing continuity with the upper layer by almost absorbing the lattice mismatch between the single crystal layer and the Si single crystal substrate 1. On the other hand, the amorphous body 2
n is an amorphous body including a microcrystalline body or a substantially homogeneous amorphous body with almost no inclusions, and as described later, sufficiently prevents the lattice mismatch with the light emitting unit 3 side. In addition, it exerts the effect of uniformly relaxing.

The temperature range suitable for growing the buffer layer 2 can be determined based on the following criteria. First, the lowest temperature is a small but single-crystal BP system at the bonding interface 4 with the Si single-crystal substrate 1.
This is the temperature at which the presence of the group III-V compound semiconductor crystal 21 is recognized, and the upper region thereof begins to appear a structure mainly composed of amorphous. If the temperature is lower than this, such a configuration cannot be obtained stably, and most of the configuration is made of the amorphous body 2n. At lower temperatures, B
Alternatively, due to the imbalance in the thermal decomposition properties of the P source, the situation is such that droplets composed of undecomposed raw materials are scattered and adhere to the surface of the Si single crystal substrate 1 only. This situation is, of course, inconvenient for the buffer layer which plays the role of making the upper layer a continuous film.

Conversely, at a high growth temperature, the island-like single crystal grains grow vigorously in the vertical (vertical) direction with respect to the surface of the Si single crystal substrate 1. Each of the pyramidal crystals developed based on this growth mode is a single crystal, but the orientation of the pyramidal crystals is not uniform. Therefore, a film formed by combining these pyramid-shaped single crystals eventually becomes a polycrystalline film in many cases. Further, the surface of the film is composed of pyramids of a pyramidal single crystal, and has a sharp uneven surface. Alternatively, sharp needle-like crystals (whisker crystals) may be randomly generated on the surface of the film. On such a buffer layer in which the orientation is disordered and the surface is in the form of a protrusion having a large difference in height, an upper layer lacking in uniformity of orientation is deposited, and is not suitable as a buffer layer. Therefore, the upper limit of the growth temperature of buffer layer 2 is determined as the temperature at which the growth of such a pyramidal single crystal is predominantly started.

The upper limit and the lower limit of the temperature suitable for obtaining the buffer layer 2 according to the present invention are determined for the reasons described above. In addition, the temperature varies depending on the plane orientation of the Si single crystal substrate 1, and varies depending not only on the epitaxial growth means but also on the configuration of the growth vessel for performing the growth reaction. Further, there is a slight variation depending on the thermal decomposability of the phosphorus (P) source. In view of these circumstances, a generally preferable temperature is in a range from 250 ° C. to 600 ° C.

FIG. 3 is a diagram for explaining the crystal defect suppressing action of the amorphous body. BP is applied to the Si single crystal substrate 1
When the buffer layer 2 having the system III-V compound semiconductor crystal 21 as the main crystal is formed, the structure of the buffer layer 2 is composed of the single crystal body 2m and the amorphous body 2b as described above. I have. Then, as shown in FIG.
A crystal defect 2t such as a misfit dislocation may be generated from a bonding interface 4 between the semiconductor layer and the buffer layer 2 due to lattice mismatch between the two. However, in this embodiment, since the buffer layer 2 is grown at a low temperature and the amorphous body 2n is formed in the upper region of the single crystal body 2m, the growth of the crystal defects 2t is suppressed by the amorphous body 2n. As a result, the crystal defects 2t propagating to the region of the amorphous body 2n are extremely small.

Therefore, this region can be constituted by a homogeneous amorphous body 2n having good crystal quality,
The homogeneous amorphous body 2n can exert an action of sufficiently and uniformly relaxing lattice mismatch. Due to the action of relaxing the lattice mismatching of the homogeneous amorphous body 2n, a group III nitride semiconductor having no lattice matching relationship with the buffer layer 2 is formed on the amorphous body 2n. Also, a crystal layer having smoothness and continuity can be laminated. For example,
A gallium nitride crystal layer may be laminated as a lower cladding layer of the light emitting portion on the buffer layer made of B _0.33 In _0.67 P (lattice constant = 5.43 °). The lattice constant of cubic gallium nitride (GaN) is 4.51 ° and B _0.33 I
Although there is no lattice matching relationship with the n _0.67 P buffer layer, even in this case, a continuous and smooth crystal layer can be provided. Further, a group III nitride semiconductor having a uniform crystal orientation can be laminated on the buffer layer 2 because of its good crystal quality and homogeneity.

Then, the BP III-V compound semiconductor crystal 21 is made of B _0.02 Ga _0.98 P
In the case of a ternary mixed crystal or a B _0.33 In _0.67 P ternary mixed crystal, a region near the bonding interface 4 with the Si single crystal substrate 1 can be formed of a single crystal that completely lattice matches with Si, Further, the existence of such a single crystal region has a sufficient effect to make the region above it a homogeneous amorphous body. Because the region below the amorphous body consists of a lattice-matched system, the amorphous body above it is more homogeneous with a lower density of crystal defects, and therefore has a continuity on the buffer layer. It is possible to more reliably form a smooth growth layer having a certain thickness.

FIG. 4 shows the structure of B laminated on the buffer layer according to the present invention.
It is a figure which shows the X-ray diffraction spectrum of a P thin film layer. Simple Si
BP as the main crystal on the (001) crystal plane of crystal substrate 1
A buffer layer 2 is formed, and a BP thin film is formed on the surface of the buffer layer 2.
Was formed at 1030 ° C, and the BP thin film was analyzed by X-ray diffraction.
Tral was observed. In addition, a buffer having this BP as a main crystal
The layer is PCl_ThreeWith a phosphorus source and BCl_ThreeWith boron source
The film was formed at 350 ° C. using the Ride VPE method. This and
As shown in FIG. 4, the X-ray diffraction spectrum of the BP film
The diffraction peak from the (004) crystal plane of the Si single crystal substrate 1
(111) appears, and (20) of the BP film
0) Diffraction peaks (116) and (220) from crystal plane
A diffraction peak (117) from the crystal plane is observed. one
One, B₁₃P _TwoThe diffraction peak from (see FIG. 14) disappeared.
ing.

That is, since the buffer layer 2 is mainly composed of cubic BP, the BP
The thin film is also a BP thin film made of a cubic crystal. This means that the buffer layer 2 in which the BP-based III-V compound semiconductor crystal as the main crystal is cubic is laminated on the buffer layer II.
This shows that a great effect can be obtained in making the group I nitride semiconductor crystal layer also a cubic system.

Further, from the result of the X-ray diffraction shown in FIG. 4, it is sufficiently understood that the crystal orientation of the BP thin film is uniform since the upper region of the buffer layer 2 is an amorphous layer. This indicates that a group III nitride semiconductor crystal having a uniform crystal orientation can be stacked on the buffer layer 2 according to the present invention, as described above. .

It should be noted that from the examples of FIGS. 4 and 14 described above,
Whether the buffer layer 2 is made of a BP-based III-V compound semiconductor crystal such as BP or a boron polyatomic boron phosphide crystal represented by B ₁₃ P ₂ as a main crystal, and the main crystal It can also be seen that the quantitative relationship between and the dependent crystal is clear from the result of X-ray diffraction analysis of the thin film laminated thereon.

FIGS. 5 and 6 are views showing a second embodiment of the present invention. This embodiment is different from the first embodiment in that the buffer layer has a multilayer structure. In this multilayer structure, crystal layers having different lattice constants are stacked to form a strained superlattice structure.

That is, the buffer layer 2a in the group III nitride semiconductor light emitting device 10a shown in FIG. 5 is formed by layering B _x Ga ₁ -XP mixed crystals having different lattice constants from each other. B having a lattice constant ΔaÅ larger than the lattice constant d around the lattice constant d (= 4.531 °)
_X1 Ga _1-X1 P mixed crystal layer (lattice constant (Å) = d + Δa) of the first layer _{20a, B X2 Ga 1-X2} P mixed crystal layer having ΔaÅ a smaller lattice constant than the lattice constant d (lattice constant (Å ) = D−Δ
a) is a second layer 21a, and the first layer 20a and the second layer 2a
1a are alternately layered. As a specific example, since the boron composition ratio X of the B _x Ga _1-x P mixed crystal lattice-matched to Si is 0.02, this boron composition ratio X = 0.
B with +0.02 and -0.02 around 02
_0.04 is a multilayer structure that combines Ga _{0. 96} P mixed crystal and GaP. Further, with the boron composition ratio X = 0.02 as the center,
The multilayer structure is a combination of a B _0.03 Ga _0.97 P mixed crystal and a B _0.01 Ga _0.99 P mixed crystal with +0.01 and −0.01. As described above, in the case of a multilayer structure, it is preferable that the boron composition ratio is increased and decreased by an equal amount with respect to a reference value (center value), and as is taught by Vegard's law, the lattice constant of Si is changed. This is because, as a criterion, by making the amount of displacement of the lattice constant in the large and small directions equal, an effect of sufficiently relaxing lattice mismatch can be exerted.

In the case of the B _x Ga _{1 -X} P mixed crystal, the maximum amount of displacement in both the large and small directions is boron, which gives a lattice constant matching that of Si, considering the condition of boron composition ratio X ≧ 0. It is ± 0.02 based on the composition ratio 0.02. Therefore, in the B _X Ga _{1 -X} P mixed crystal, the possible range of the boron composition ratio X is 0 ≦ X ≦ 0.04. The order of lamination of the first layer 20a and the second layer 21a and the number of layers can be arbitrarily set. However, it is avoided that GaP when X = 0 is directly laminated on the Si single crystal substrate 1. It is the Si single crystal substrate 1
On the other hand, it is difficult to grow a flat and continuous good film of GaP, while the BP-based film is compatible with the Si single crystal substrate 1 and can be grown as a good film.

Group III nitride semiconductor light emitting device 1 shown in FIG.
The buffer layer 2b at 0b has a lattice constant different from that of B
_This is a layer in which _Y In _{1 -Y} P mixed crystals are layered. Similar to the case of FIG. 5, the lattice constant d of Si on the substrate side (= 4.531)
Å), the first layer 20b is a B _Y1 In _1-Y1 P mixed crystal layer having a lattice constant ΔbÅ larger than the lattice constant d, and B _Y2 I having a lattice constant ΔbÅ smaller than the lattice constant d.
The n _{1 -Y2} P mixed crystal layer is referred to as a second layer 21b, and the first layer 20b
And the second layer 21b are alternately layered. Since the boron composition ratio Y of the B _Y In _1-Y P mixed crystal lattice-matched to Si is 0.33, this boron composition ratio Y = 0.
It is configured such that Y is displaced equally in two directions, large and small, about the center 33.

In the case of this B _Y In _1-Y P mixed crystal, the maximum amount displaced in both the large and small directions is, considering the condition of the boron composition ratio Y ≧ 0, the boron composition which gives a lattice constant matching that of Si. It is ± 0.33 based on the ratio 0.33. Therefore, in the B _Y In _1-Y P mixed crystal, the range in which the boron composition ratio Y can be taken is 0 ≦ Y ≦ 0.66. Further, as in the case of FIG. 5, the first layer 20b and the second layer 2
The order of lamination with 1b and the number of layers can be arbitrarily set.

FIG. 7 is a diagram showing a third embodiment of the present invention. This embodiment is different from the first embodiment in that an intervening layer 9 is provided between the buffer layer 2 and the light emitting section 3. This intervening layer 9 is for ensuring the lattice matching between the buffer layer 2 and the lower cladding layer of the light emitting section 3. The buffer layer 2 is formed at a relatively low temperature of 600 ° C. or less. On the other hand, it is formed at a higher temperature, for example, around 900 ° C. Materials suitable for forming the intervening layer 9 include a range of possible lattice constants of 3.62 ° or more and 4.5 or more.
Boron phosphide nitride of 4 ° or less (BP ₁ -ZN _Z : 0 ≦ Z ≦
1) There is a mixed crystal. Depending on the nitrogen composition ratio Z, a crystal layer lattice-matched to an aluminum-gallium nitride mixed crystal (Al _A Ga _B N: 0 ≦ A, B ≦ 1, A + B = 1) suitable for forming the lower cladding layer is formed. This is because they can be supplied. For example,
BP _{0. 97} N _0.03 mixed crystal nitrogen composition ratio of 0.03 is lattice matched to the cubic GaN (lattice constant = 4.51Å),
A BP _0.83 N _0.17 mixed crystal with a nitrogen composition ratio of 0.17 is lattice-matched to cubic AlN (lattice constant = 4.38 °).

Also, from the lattice matching with the lower cladding layer, boron phosphide (BP) or boron phosphide / gallium (BG)
aP) is also a material suitable for forming the intervening layer 9.

Further, boron arsenide (BAs _1-W N _W : 0)
≦ W ≦ 1) A mixed crystal is also a material suitable for forming the intervening layer 9. 3 composed of boron arsenide (BAs: lattice constant = 4.78 °) and boron nitride (BN: lattice constant = 3.62 °)
By forming the intermediate layer 9 from BAs _1-W N _W is the original mixed crystal, the range of possible lattice constant of the intermediate layer 9 is 3.
It is 62 ° or more and 4.78 ° or less, and can be lattice-matched with a group III nitride semiconductor crystal that did not have lattice matching with the above-mentioned boron nitrided phosphide BP ₁ -ZN _Z , so that the group III nitride having lattice matching can be achieved. Kinds of semiconductor crystals can be increased. For example, BAs having an arsenic composition ratio of 0.81
_0.81 N _0.19 cannot be achieved by the above BP ₁ -ZN _Z mixed crystal. For example, Ga _0.90 with an indium composition ratio of 10% is used.
Lattice matching can be achieved with In _0.10 N (lattice constant = 4.56 °).

The intervening layer 9 may be formed with a single composition as described above, or a composition may be provided with a gradient, and a composition that lattice-matches with the buffer layer 2 on the bonding interface side with the buffer layer 2. Alternatively, the composition may be formed so as to have a composition lattice-matched to the lower cladding layer on the bonding interface side with the lower cladding layer.

In each of the above embodiments, it is preferable that the buffer layer 2 is also made conductive because the light emitting portion 3 made of a conductive crystal layer is provided on the conductive Si single crystal substrate 1. In order to add conductivity to the buffer layer 2, doping may be performed at the time of film formation. The n-type buffer layer 2 can be formed by doping n-type impurities such as Si and tin Sn belonging to group IV of the periodic table and selenium Se and sulfur S of group VI, and zinc Zn, beryllium of group II A p-type buffer layer 2 can be provided by doping with a p-type impurity such as Be, magnesium Mg, or group IV carbon C.

The thickness of the buffer layer 2 is less than a few μm, especially 50 μm.
It is desirable that the angle be 0 ° or less. In the region of the bonding interface 4 with the Si single crystal substrate 1, a function as a buffer layer can be sufficiently exhibited if the thickness is at least about several atomic layers.

In each of the above embodiments, an ohmic electrode is laid on one surface of the Si single crystal substrate 1 opposite to the buffer layer 2 side. A p-type Si single crystal is provided with a p-type ohmic electrode, and an n-type Si single crystal is provided with an n-type ohmic electrode. These electrodes are made of a known ohmic electrode material such as aluminum. As described above, by utilizing the advantage of using the conductive Si crystal for the substrate 1, a positive or negative ohmic electrode can be arranged on the Si single crystal substrate 1 to form a light emitting element such as an LED or an LD. . Unlike a conventional laminated structure using insulating sapphire as a substrate, there is no need to lay two ohmic electrodes on the same surface side. Therefore, the light emitting area is required to form both p-type and n-type electrodes. It is not necessary to delete (pn junction area). Therefore, a reduction in the light emitting area can be avoided, and a light emitting element having a larger light emitting area with the same chip size can be provided.

Further, since diamond crystal type Si having clear cleavage in the [011] crystal direction is used as the substrate 1, an LD is formed from the laminated structure formed on the Si single crystal substrate 1. In such a case, the optical resonance surface composed of the {011} plane can be easily formed by its cleavage.

As described above, in the embodiment according to the present invention, the buffer layer 2 on the Si single crystal substrate 1 is
A boron polyatomic boron phosphide crystal (B _x P _Y : X ≧ 6, 0 <Y ≦ 2) in which the group-V compound semiconductor crystal 21 is the main crystal and the composition ratio of the boron element and the phosphorus element is 6: 1 or more. ) 22 was formed so as to be a subordinate crystal, and a light emitting portion 3 made of a group III nitride semiconductor was laminated on the buffer layer 2. Since buffer layer 2 is mainly composed of cubic BP-based III-V compound semiconductor crystal 21, light-emitting portion 3 in the upper layer can be formed as a cubic crystal. Therefore, group III nitride semiconductor light-emitting device In the above, various effects exhibited by using a conductive cubic Si single crystal for the substrate 1, that is, a wider light emitting area can be secured, an optical resonance surface in an LD can be easily formed, and further, a pn junction Various effects such as a low-resistance p-type conductive layer constituting the light-emitting portion 3 of the mold can be easily formed.

In view of the structure of the buffer layer 2, the single crystal 2m is formed on the bonding interface 4 side with the Si single crystal substrate 1 and the amorphous body 2n is formed on the upper layer. Therefore, the single-crystal body 2m on the bonding interface 4 side substantially absorbs the lattice mismatch between the single-crystal body 1 and the Si single-crystal substrate 1 to provide continuity with the upper layer. Therefore, the buffer layer 2 has a function of sufficiently and evenly mitigating the lattice mismatch with the light emitting portion 3 side, so that even a group III nitride semiconductor having no lattice matching relationship with the buffer layer 2 can be smoothed. Thus, a crystal layer having continuity can be laminated. In addition, because of the good crystal quality and homogeneity of the amorphous body 2n, a group III nitride semiconductor having a uniform crystal orientation can be stacked on the buffer layer 2.

Further, since the subordinate boron polyatomic boron phosphide crystal 22 accounts for 10% or less of the entire buffer layer 2, the influence of the hexagonal crystal hardly affects the light emitting portion 3, but the light emitting portion 3 3 can be more preferably configured as a cubic crystal.

Since the main crystal BP-based III-V compound semiconductor crystal 21 is formed of a mixed crystal of boron phosphide / gallium or a mixed crystal of boron phosphide / indium,
Perfect lattice matching with Si of the substrate 1 can be realized, and therefore, the growth layer laminated on the buffer layer 2 can be made smoother and more continuous.

Further, since the buffer layer 2 is formed by superposing the main crystals having different compositions, lattice matching with the Si single crystal substrate 1 can be realized by the action of the strained superlattice.
It can serve as a buffer layer.

Further, since the intervening layer 9 is provided between the buffer layer 2 and the light emitting section 3, the lattice matching with the light emitting section 3 side can be made more complete, and Can be made more complete without crystal defects.

Next, the group III nitride semiconductor light emitting device of the present invention will be described with reference to more specific examples.

[0070]

FIG. 8 is a diagram showing a cross-sectional structure of an LED according to a first embodiment of the present invention. In this embodiment,
On a p-type (001) -Si single crystal substrate 101 doped with boron (B), a laminated structure including a buffer layer 102 made of a mixed crystal of boron phosphide and gallium is formed. A group III nitride semiconductor light emitting device (LED) 100 that outputs visible light of a wavelength was configured.

The buffer layer 102 was a p-type BGaP mixed crystal layer doped with zinc (Zn). The mixed crystal layer was composed of a B _0.02 Ga _0.98 P mixed crystal having a boron composition ratio of 0.02 which gives a lattice constant (5.431 °) corresponding to Si.
The BGaP buffer layer 102 having a thickness of 150 ° is made of diborane (B ₂ H ₆ ) / trimethylgallium ((CH ₃ ) ₃ Ga).
It was grown by a reduced pressure MOCVD method using a / phosphine (PH ₃ ) / hydrogen growth reaction system. In order to mainly configure the region near the bonding interface with the Si single crystal substrate 101 with a single crystal,
The film was formed at a low temperature of 380 ° C. Zn doping sources include:
Diethyl zinc ((C ₂ H ₅ ) ₂ Zn) (100 volume pp
m) - Using hydrogen (H _2).

Si single crystal substrate 101 and B _0.02 Ga _0.98 P
A region approximately 30 ° from the junction interface 104 with the buffer layer 102 was a single crystal region 102m mainly composed of a single crystal. The region extending over about 120 ° is an amorphous body region 102n mainly composed of an amorphous body.

On the B _0.02 Ga _0.98 P buffer layer 102, M
g-doped p-type Al _0.10 Ga _0.90 N mixed crystal layer (layer thickness = 0.7
5 μm, lower cladding layer 103 a of carrier concentration = 2.0 × 10 ¹⁷ cm ⁻³ ), Si-doped n-type Ga _0.90 I
n _0.10 N (layer thickness = 0.10 μm, carrier concentration = 1.5
× 10 ¹⁸ cm ⁻³ ) light-emitting layer 103b and n-type G
aN (layer thickness = 3.0 μm, carrier concentration = 3.5 × 10
^An upper cladding layer 103c having a thickness of ¹⁸ cm ^-3 ) was sequentially laminated, and a light emitting portion 103 having a pn junction type DH structure was overlaid.
The contact layer 106 on the upper cladding layer 103c
It consisted of a g-doped p-type GaN layer.

After constructing the LED 100, the buffer layer 1
X-ray diffraction analysis of the composition of the buffer layer 102
The amount of the boron polyatomic boron phosphide crystal represented by B ₁₃ P ₂ is very small (less than 1%) from the B _0.02 Ga _0.98 P mixed crystal layer that constitutes Was confirmed.

Further, since the buffer layer 102 is made of a material that is lattice-matched with Si of the substrate 101, each of the upper layers has particularly excellent continuity and exhibits a cubic crystal form. . Observation of crystal defects by the cross-sectional TEM method showed that the buffer layer 102 was effective in reducing the density of misfit dislocations and the like that propagate to the upper light emitting portion 103. The light emitting section 1 is formed from a region near the bonding interface 104 between the Si single crystal substrate 101 and the buffer layer 102.
The density of dislocations penetrating into the lower cladding layer 103a constituting the layer No. 03 is 10 ⁴ c higher than that of the conventional sapphire substrate / group III nitride semiconductor buffer layer lamination system.
It was remarkably reduced from m ⁻² to 10 ⁵ cm ⁻² .

A positive ohmic electrode 107 is formed on the back surface of the p-type conductive Si substrate 101, and a negative ohmic electrode 10 having a diameter of about 110 μm is formed on the surface of the contact layer 106.
8 were provided to configure the LED 100. This LED 100
An operating current was passed in the forward direction to emit blue light. When the forward current is 20 mA, the emission wavelength is about 430 nm.
The half width of the emission spectrum was about 14 nm. The light emission intensity in the chip state measured using a general integrating sphere is 1
6 microwatts (μW). Forward voltage (V
f) is about 2.7 V and the reverse voltage (Vr) is 1
It was as excellent as 5 V or more, and it was recognized that good pn junction characteristics were manifested.

(Second Embodiment) FIG. 9 is a view showing a sectional structure of an LED according to a second embodiment of the present invention. In the present embodiment, the constituent material of the buffer layer 202 is the B material described in the first embodiment.
_The LED 200 was constructed by changing from _0.02 Ga _0.98 P mixed crystal to B _0.33 In _0.67 P mixed crystal.

The buffer layer 202 is made of zinc (Zn)
P-type B_0.33In_0.67It consisted of a P mixed crystal layer. Layer thickness
The BInP buffer layer 102 of which
(B_TwoH₆) / Phosphine (PH_Three) / Hydrogen growth reaction system
Formed at 450 ° C by a general atmospheric pressure MOCVD method
Filmed. As a Zn doping source, diethyl zinc ((C
_TwoH_Five)_TwoZn) (100 ppm by volume) -hydrogen (H_Two)use
Used.

A region approximately 30 ° from the junction interface 204 between the Si substrate 201 and the B _0.33 In _0.67 P buffer layer 202 was a single crystal region 202m mainly composed of a single crystal. The region extending over about 120 ° is an amorphous body region 202n mainly composed of an amorphous body. After the LED 200 was formed, no X-ray diffraction peak attributed to B ₆ P or B ₁₃ P ₂ was recognized from the B _0.33 In _0.67 P mixed crystal layer forming the buffer layer 202.

On the B _0.33 In _0.67 P buffer layer 202, the light emitting section 203 having the pn junction type DH structure described in the first embodiment and the contact layer 206 were formed in an overlapping manner. Substrate 20
Buffer layer 202 from a material lattice-matched to Si
, Each of the upper layers was particularly excellent in continuity and exhibited a cubic crystal form.

An LED 200 was constructed by providing a positive ohmic electrode 207 on the back surface of a p-type conductive Si substrate 201 and a negative ohmic electrode 208 having a diameter of about 110 μm on the surface of the contact layer 206. This LED200 has 2
By passing a forward current of 0 mA, the emission wavelength becomes about 450
Blue emission was obtained with a nm. The half width of the emission spectrum was about 13 nm. The forward voltage is about 2.7 V (at2
0 mA) and the reverse voltage is as high as 15 V (at 10 μA)
And an LED having excellent pn junction characteristics (rectifying properties) was provided.

(Third Embodiment) FIG. 10 is a view showing a sectional structure of an LED according to a third embodiment of the present invention. In this embodiment, an n-type (00) doped with antimony (Sb) is used.
1) A stacked structure including a buffer layer 302 having a strained superlattice structure was formed on a -Si single crystal substrate 301, and an LED 300 was formed from the stacked structure.

In this embodiment, the buffer layer 302 is made of BCl
400 ° C by ₃ / PCl ₃ / H ₂ halogen VPE method
To form a strained superlattice type multilayer structure of B _0.04 Ga _0.96 P mixed crystal and gallium phosphide (GaP). That is, S
An undoped n-type B _0.04 Ga _0.96 P mixed crystal layer 320 was first deposited on the surface of the b-doped Si single crystal substrate 301 to form a lowermost layer of the buffer layer 302. Undoped n-type B _0.04 Ga
_{On the 0.96} P mixed crystal layer 320, a Si layer having a thickness of about 50 ° is formed.
A doped n-type GaP layer 321 has been deposited. This B _0.04
After the multilayer structure of the Ga _0.96 P mixed crystal layer 320 / GaP layer 321 was repeatedly stacked twice, the B _0.04 Ga _0.96 P mixed crystal layer 320 was further laminated, and the whole was used as the buffer layer 302.

The lowermost layer B _0.04 Ga _0.96 P of the buffer layer 302
The mixed crystal layer 320 reduces the content of a boron polyatomic boron phosphide crystal represented by B ₁₃ P ₂ to less than about 1/30 based on an analysis by an electron beam diffraction method after the LED 300 is formed. It was found that most of them were composed of cubic BGaP crystals. In addition, the Si single crystal substrate 3
The region near the bonding interface 304 with No. 01 was composed of a face-centered cubic lattice type BP single crystal.

The light emitting portion 303 on the buffer layer 302 having a strained superlattice structure has a Si-doped n-type GaN layer (layer thickness = 3.2 μm, carrier concentration =
3.0 × 10 ¹⁸ cm ⁻³ ), n-type Ga _0.90 In doped with zinc (Zn) and Si as the light emitting layer 303 b
_0.10 N layer (layer thickness = 0.08 μm, carrier concentration = 2.0
× 10 ¹⁸ cm ⁻³ ) and an Mg-doped p-type Al _0.10 Ga _0.90 N layer (layer thickness = 0.0) as the upper cladding layer 303c.
2 μm, carrier concentration = 1.4 × 10 ¹⁷ cm ⁻³ ) were sequentially laminated.

The light emitting portion is provided on the surface of the buffer layer 302 according to the present invention.
The light emitting unit 303 is configured by stacking the 303.
Each of the layers 303a, 303b, 303c is a continuous film
Could be configured. The outermost layer of the buffer layer 302
Si-doped n-type B _0.04Ga_0.96P mixed crystal layer 32
0 does not include any hexagonal boron polyatomic boron phosphide crystal
, The light emitting portion 303 has a cubic structure.
It was composed of a crystal layer.

The Mg-doped p on the upper cladding layer 303c
GaN layer (layer thickness = 0.12 μm, carrier concentration = 1.1.
On the contact layer 306 made of 5 × 10 ¹⁸ cm ⁻³ ), a p-type ohmic electrode 307 having a multilayer structure of gold (Au) and nickel (Ni) oxide was arranged. Also,
On the back surface of the Sb-doped Si single crystal substrate 301, an n-type ohmic electrode 308 made of an aluminum (Al) · Sb alloy is disposed by utilizing the conductivity of the substrate 1, and an LED 300 that supplies an operating current in the vertical direction is provided. Done

An operating current was passed through the LED 300 in the forward direction to emit blue light. When the forward current was 20 mA, the emission wavelength was about 450 nm, and the half width of the emission spectrum was about 12 nm. The light emission intensity in a chip state measured using a general integrating sphere is 18 microwatts (μ
W). The forward voltage (Vf) was about 2.7 V, and the reverse voltage (Vr) was as excellent as 15 V or more, and it was recognized that good pn junction characteristics were exhibited.

(Fourth Embodiment) FIG. 11 is a view showing a sectional structure of an LED according to a fourth embodiment of the present invention. In this embodiment, n-type (100) -S doped with phosphorus (P) is used.
Buffer layer 4 made of boron phosphide on i single crystal substrate 401
02 and an intervening layer 409 were formed, and an LED 400 was formed from the laminated structure.

The buffer layer 402 is made of boron trichloride (BCl_Three)
/ Phosphorus trichloride (PCl_Three) / Hydrogen (H _Two) Using a reaction system
Grown at 350 ° C by a general halogen VPE method.
N-type boron phosphide having a layer thickness of 200 °
(BP) layer. BCl _ThreePC1 for_ThreeCompanion
Ratio of the amount of supply (= PCl_Three/ BCl_ThreeRatio) is 100 times
Set. When forming the buffer layer 402, disilane (5
Product ppm) -Doping Si using hydrogen mixed gas
did. Among the buffer layers 402, the Si single crystal substrate 401
A region of about 30 ° from the joining surface 404 with BP is made of BP.
The single crystal body region is 402 m, and the further upper region is BP
As an amorphous body region 402n. Single crystal
B in the body region 402m₆P or B₁₃P_TwoOr B_14.7P
_0.3 The existence of boron polyatomic boron phosphide crystals such as
It was not detected by fold analysis.

On the surface of the buffer layer 402, the halide VP
A boron phosphide (BP) layer is formed at 960 ° C.
09. The layer thickness was 0.2 μm. Also,
By doping Si using a mixed gas of disilane (5 ppm by volume) and hydrogen at the time of film formation, the intervening layer 409 was made an n-type crystal layer. Since the amount of boron polyatomic boron phosphide crystal typified by B ₁₃ P ₂ contained in the lower buffer layer 402 was less than 1%, this BP intervening layer 40
9 was a cubic crystal and became a smooth continuous film.

On the BP intervening layer 409, a Si-doped n-type gallium nitride (GaN) layer (layer thickness = 1.0 μm, carrier concentration = 2.2 × 10 ¹⁸ cm ⁻³ ), undoped n-type Ga
_0.94 In _0.06 N layer (layer thickness = 0.06 μm, carrier concentration = 1.8 × 10 ¹⁸ cm ⁻³ ), and Mg-doped p-type Al
_0.90 Ga _0.10 N layer (layer thickness = 0.10 μ, carrier concentration =
1.2 × 10 ¹⁷ cm ⁻³ ), each having a cubic crystal layer. An n-type GaN crystal layer is used as a lower cladding layer 403a, an n-type Ga _0.94 In _0.06 N crystal layer is used as a light emitting layer 403b, and a p-type A1 _0.90 Ga _0.10 N crystal layer is used as an upper cladding layer 403c. The light emitting unit 403 having the junction type DH structure was formed. The contact layer 406 on the p-type cladding layer 403c is a Mg-doped p-type GaN layer (layer thickness = 0.10 μm, carrier concentration = 8.2).
× 10 ¹⁷ cm ^-3 ).

A positive ohmic electrode 407 made of gold (Au) having a diameter of about 120 μm is provided on the surface of the contact layer 406, and aluminum (Al) is formed on almost the entire back surface of the n-type conductive Si single crystal substrate 401. An LED 400 was provided by providing a negative ohmic electrode 408 made of Al).

An operating current was passed between the ohmic electrodes 407 and 408 in the forward direction to emit blue-violet light. When the forward current was set to 20 milliamperes (mA), the emission wavelength was measured at about 430 nanometers (nm). The half width of the emission spectrum was about 12 nm, which was sufficient to provide emission with excellent monochromaticity. The forward voltage (Vf) is
The value was particularly low at 2.6 volts. In addition, the reverse voltage value is 15 V or more (at 10 microamps (μ
A)) and a high value indicating that good pn junction characteristics were formed.

(Fifth Embodiment) FIG. 12 is a view showing a sectional structure of an LED according to a fifth embodiment of the present invention. In the present embodiment, the constituent materials of the buffer layer 502 and the intervening layer 509 are
Boron phosphide / gallium mixed crystal (B
_0.02 Ga _0.98 P) to construct LED500.

The boron composition ratio for forming the buffer layer 502 is set to 0.1.
The n-type B _0.02 Ga _0.98 P mixed crystal layer of 02 has a boron (B) source of trimethylboron ((CH ₃ ) ₃ B), a gallium (Ga) source of trimethylgallium ((CH ₃ ) ₃ Ga), A film was formed at 450 ° C. by a normal atmospheric pressure MOCVD method using phosphine (PH ₃ ) and phosphine (PH ₃ ) as a source. In order to obtain the n-type buffer layer 502, Si was doped at the time of film formation using disilane as a doping gas. The content of the boron polyatomic boron phosphide crystal represented by B ₁₃ P ₂ in the buffer layer 502 was less than 1%. Among the buffer layer 502 to about 100Å for layer thickness, the region of about 20Å from the bonding interface 504 between the Si single crystal substrate 501 formed as a single crystal region 502m consisting B _{0. 02} Ga _0.98 P mixed crystal, Further, a region thereabove was formed as an amorphous body region 502n made of a B _0.02 Ga _0.98 P mixed crystal.

[0097] On the surface of the buffer layer 502, in to 950 ° C. in the same manner as in the fourth embodiment, by laminating a n-type B _{0. 02} Ga _0.98 P mixed crystal as an intervening layer 509. Since the amount of boron polyatomic boron phosphide crystal typified by B ₁₃ P ₂ contained in the lower buffer layer 502 was less than 1%, this B _0.02 Ga _0.98
The P mixed crystal intervening layer 509 was cubic and became a smooth continuous film.

N-type B _0.02 G with lattice constant of 4.51 °
On the surface of a _0.98 P mixed crystal intervening layer 509, n-type GaN having a lattice constant of 4.51 ° is also formed on lower cladding layer 503.
A light emitting unit 5 similar to that described in the fourth embodiment, including
03 was laminated. That is, the lattice matching between the buffer layer 502 and the lower cladding layer 503a is further ensured by the intervening layer 509. The fourth p-type AlGaN cladding layer 503c constituting the light emitting portion 503 has
As in the embodiment, the contact layer 50 made of p-type GaN is used.
6 was laminated. Thus, a laminated structure for an LED was constructed. Each of the constituent layers constituting the laminated structure was cubic, and was a continuous film. Gold (A) having a diameter of about 120 μm is formed on the surface of the contact layer 506.
The positive ohmic electrode 507 made of u) was provided, and the negative ohmic electrode 508 made of aluminum (Al) was provided on substantially the entire back surface of the n-type conductive Si single crystal substrate 501 to constitute the LED 500.

The LED 500 emitted blue-violet visible light of about 430 nm when an operating current of 20 mA was passed in the forward direction. The half width of the emission spectrum was about 14 nm. The forward voltage (Vf) was about 2.7 V, and the reverse voltage (Vr) was as excellent as 15 V or more.

(Sixth Embodiment) FIG. 13 is a view showing a sectional structure of an LD according to a sixth embodiment of the present invention. In this embodiment, the same Zn-doped p-type B _0.02 Ga as described in the first embodiment is used.
_{On the} buffer layer 602 made of _0.98 P mixed crystal, an intervening layer 609 made of BP _K N _1-K (0 <K ≦ 1) in which the phosphorus composition ratio K is reduced in the thickness direction is inserted to form a laminated structure. Then, a laser diode (LD) 600 as a group III nitride semiconductor light emitting device was formed from the laminated structure.

The intervening layer 609 is a crystal layer provided to ensure the lattice matching between the buffer layer 602 and the lower cladding layer 603a.
Was formed. The phosphorus composition ratio K of the intervening layer 602 is
1.0 at the bonding interface 605 with the layer No. 02 and a layer thickness of 0.50
The thickness was 0.97 on the surface of the intervening layer 609 having a thickness of μm. The phosphorus composition ratio K is determined by keeping the supply amounts of B ₂ H ₆ as the boron (B) source and PH ₃ as the phosphorus source to the MOCVD reaction system constant, while maintaining the supply amount of NH _{3 as} the nitrogen (N) source. The supply amount was increased at a constant rate over time. Also, the intervening layer 60
No. 9 formed a p-type crystal layer by doping Zn with a mixture of diethyl zinc (100 ppm by volume) and hydrogen as a doping source of Zn at the time of film formation. This p-type intervening layer 609 is a continuous film, and thus has contributed to making the upper layer a continuous film.

On the BP _0.97 N _0.03 layer having a lattice constant of 4.51 ° constituting the surface of the intervening layer 609, a p-type gallium nitride (GaN) crystal mainly composed of a cubic crystal having a lattice constant identical to that of the BP _0.97 N _0.03 layer The lower clad layer 603a made of was laminated. This lower cladding layer 603a is made of a normal pressure MOCV
The film was formed at 850 ° C. by the method D, and the carrier concentration was changed to biscyclopentadienyl Mg (b
is- (C ₅ H ₅₎ was adjusted with a feed to MOCVD reaction system ₂ Mg). Since the lower cladding layer 603a made of GaN crystal is mainly composed of a cubic crystal, the carrier concentration is reduced to about 1 × 1 by doping with Mg.
A p-type layer of 0 ¹⁸ cm ^-3 was easily provided. The layer thickness was about 2.5 μm.

On the cubic GaN crystal layer constituting the lower cladding layer 603a, a cubic gallium indium nitride mixed crystal (Ga) having a small inconsistency with GaN and an indium (In) composition ratio of 0.06 is used. _A light emitting layer 603b made of _0.94 In _0.06 N) was laminated. The light emitting layer 603b was undoped to have a carrier concentration of about 3 × 10 ¹⁸ cm ⁻³ and a layer thickness of about 0.1 μm. Ga _0.94 forming the light emitting layer 603b
Since the lattice constant of the In _0.06 N mixed crystal layer is 4.54 ° and the lattice constant of GaN constituting the lower cladding layer 603a is 4.51 °, the degree of lattice mismatch (degree of mismatch) is about 0 °. .67%. Incidentally, conventional hexagonal GaN (lattice constant =
3.180 °) and the lattice constant is 3.
The degree of lattice mismatch in a laminated system with a hexagonal Ga _0.94 In _0.06 N mixed crystal layer determined to be 209 ° reaches about 10.2%.

On the surface of the light emitting layer 603b, an Si-doped n-type GaN crystal layer was laminated as an upper cladding layer 603c. The carrier concentration is adjusted by the supply amount of a disilane (Si ₂ H ₆ ) -hydrogen mixed gas as a Si doping source to the MOCVD reaction system, and is about 3.0 × 10 ¹⁸ cm ^−3.
And The layer thickness was 0.50 μm. The upper cladding layer 603c made of cubic GaN was also formed by the normal pressure MOCVD method similarly to the light emitting layer 603b. A p-type GaN crystal layer having a layer thickness of 0.8 μm and a carrier concentration of 1.5 × 10 ¹⁸ cm ⁻³ was laminated on the upper cladding layer 603c to form a current confinement layer 610.

According to a cross-sectional TEM observation using a transmission electron microscope (TEM), B ₁₃ P ₆ is formed in a very small region of the bonding interface 604 between the Si single crystal substrate 601 and the buffer layer 602.
Microcrystals presumed to be were observed. However, the buffer layer 60
No boron polyatomic boron phosphide crystals were observed in the upper region of No. 2. Further, at the time of film formation at a low temperature, a region mainly composed of a single crystal, which has been limited to the vicinity of the bonding interface 604 with the Si single crystal substrate 601, is almost entirely formed after the upper layer is laminated at a higher temperature. It was composed of crystals.

The current confinement layer 61 which is the outermost layer of the laminated structure
After opening 0 in a band (stripe) shape, a band-shaped negative ohmic electrode 608 made of gold (Au) is connected to the current constriction eyebrow 61.
It was arranged so as to be in contact with the surface of the upper cladding layer 603c via the center line 0. On the other hand, a p-type positive ohmic electrode 607
Was provided on the back side of the cubic p-type Si single crystal substrate 601 as a "solid" full-surface electrode. Then, rectangular chips were formed using cutting lines orthogonal to each other on the surface of the laminated structure. Si single crystal substrate 6 of diamond crystal structure type
01 originally has a cleavage property in the [011] direction.
Chips could be easily formed with little chipping. In addition, since the end face on the short side of the chip is also formed of a smooth and mirror-like cleavage plane, it can be used as an optical resonance plane.

With the chip placed on the copper heat sink, a forward voltage was applied. Blue laser light oscillation was obtained with a threshold voltage of about 20 A / cm ² . The oscillation wavelength is about 44
It became 0 nm.

[0108]

Since the present invention has the above-described configuration,
The following effects can be obtained. In the invention according to claim 1, the buffer layer on the silicon single crystal substrate is
Boron polyatomic boron phosphide crystal (B _x P _Y : X ≧ 6, 0 <Y) in which a BP-based III-V compound semiconductor crystal is a main crystal and a composition ratio of a boron element and a phosphorus element is 6: 1 or more. ≦ 2) was formed as a subordinate crystal, and a light emitting portion made of a group III nitride semiconductor was laminated on this buffer layer. As described above, since the buffer layer is mainly composed of a cubic BP-based III-V compound semiconductor crystal, the light emitting portion of the upper layer can also be formed as a cubic crystal. Therefore, the group III nitride semiconductor light emitting device In the above, various effects exhibited by using a conductive cubic silicon single crystal for the substrate, that is, a light emitting area can be secured wider, an optical resonance surface in a laser diode can be easily formed, and further, a pn junction Various effects such as easy formation of a low-resistance p-type conductive layer constituting the light-emitting portion can be sufficiently exhibited, and a III-nitride semiconductor light-emitting device having good luminous efficiency and excellent luminous intensity can do.

According to the second aspect of the present invention, the buffer layer is made of a single crystal at the junction interface side with the silicon single crystal substrate and an amorphous material at the upper layer side. The single crystal body substantially absorbs the lattice mismatch between the single crystal body and the silicon single crystal substrate to provide continuity in the upper layer, and the amorphous body has a lattice with the light emitting portion side because of its homogeneity. It can sufficiently and uniformly reduce the mismatch, and can form a smooth and continuous crystal layer even with a group III nitride semiconductor that does not have a lattice matching relationship with the buffer layer. . In addition, because of the good crystal quality and homogeneity of the amorphous body, it is possible to stack a group III nitride semiconductor having a uniform crystal orientation on the buffer layer. The group III nitride semiconductor light emitting device can have high luminous efficiency and excellent luminous intensity.

Furthermore, according to the third aspect of the present invention, since the subordinate crystal of boron polyatomic boron phosphide is made to be 10% or less of the entire buffer layer, the influence of the hexagonal crystal does not affect the light emitting portion. It is almost inferior, and the light emitting portion can be more preferably configured as a cubic crystal.

According to the fifth and sixth aspects of the present invention,
Since the main crystal of the BP-based III-V compound semiconductor crystal is formed of a mixed crystal of boron phosphide and gallium, or a mixed crystal of boron phosphide and indium, perfect lattice matching with silicon of the substrate can be realized. Therefore, the growth layer laminated on the buffer layer can be made smoother and more continuous.

Further, in the invention according to claim 7, since the buffer layer is formed by superposing the main crystals having different compositions, lattice matching with the silicon single crystal substrate can be realized by the action of the strained superlattice. As in the case of the layer, it can serve as a buffer layer.

According to the eighth aspect of the present invention, since the intervening layer is provided between the buffer layer and the light emitting section, the lattice matching with the light emitting section side can be further improved.
This can contribute to making the crystal structure of the light emitting portion more complete without crystal defects.

Further, in the invention according to the tenth aspect, since the composition of the intervening layer is graded, lattice matching is performed with the buffer layer on the bonding interface side with the buffer layer, and the light emitting section is formed on the bonding interface side with the light emitting section. And the lattice matching can be further ensured.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a part of a laminated structure of a group III nitride semiconductor light emitting device of the present invention.

FIG. 2 is a diagram schematically showing a tissue configuration of a buffer layer.

FIG. 3 is a diagram for explaining a crystal defect suppressing action of an amorphous body.

FIG. 4 is a view showing an X-ray diffraction spectrum of a BP thin film layer laminated on a buffer layer according to the present invention.

FIG. 5 is a diagram showing a second embodiment of the present invention.

FIG. 6 is a diagram showing a second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a diagram showing a cross-sectional structure of the LED according to the first embodiment of the present invention.

FIG. 9 is a view showing a sectional structure of an LED according to a second embodiment of the present invention.

FIG. 10 is a diagram showing a sectional structure of an LED according to a third embodiment of the present invention.

FIG. 11 is a diagram showing a sectional structure of an LED according to a fourth embodiment of the present invention.

FIG. 12 is a view showing a sectional structure of an LED according to a fifth embodiment of the present invention.

FIG. 13 is a view showing a sectional structure of an LD according to a sixth embodiment of the present invention.

FIG. 14 is a diagram showing an X-ray diffraction spectrum of a boron phosphide film formed on a buffer layer mainly composed of boron polyatomic boron phosphide.

[Explanation of symbols]

Reference Signs List 1 Si single crystal substrate 2 Buffer layer 21 BP-based III-V compound semiconductor crystal 22 Boron polyatomic boron phosphide crystal 2m Single crystal 2n Amorphous 2t Crystal defect 2a Multilayered buffer layer 20a First layer 21a First layer Double layer 2b Buffer layer 20b having a multilayer structure 20b First layer 21b Second layer 3 Light emitting portion 4 Junction interface between Si single crystal substrate and buffer layer 9 Intervening layer 10 Group III nitride semiconductor light emitting device 100, 200, 300, 400, 500 LED 600 LD 101, 201, 301, 401, 501, 601
Si single crystal substrate 102, 202, 302, 402, 502, 602
Buffer layer 103, 203, 303, 403, 503, 603
Light emitting units 104, 204, 304, 404, 504, 604
Bonding interface between Si single crystal substrate and buffer layer 106, 206, 306, 406, 506, 606
Contact layers 107, 207, 307, 407, 507, 607
Positive ohmic electrodes 108, 208, 308, 408, 508, 608
Negative ohmic electrode 610 Current confinement layer

Claims (10)

[Claims] 1. A group III nitride semiconductor light emitting device comprising a light emitting portion made of a group III nitride semiconductor laminated on a conductive silicon single crystal substrate via a buffer layer, wherein the buffer layer is made of a group III element And the group V element by 1
The BP-based III-V compound semiconductor crystal according to-one mainly crystals, allocations to 6: 1 or more to boron polyatomic boron phosphide crystal boron element and phosphorus element _{(B x P Y: X ≧} 6 , 0 <
A group III nitride semiconductor light-emitting device, wherein Y ≦ 2) is formed as a dependent crystal. 2. The III according to claim 1, wherein the buffer layer is a single crystal at a bonding interface side with the silicon single crystal substrate and is an amorphous body at an upper layer side. Group nitride semiconductor light emitting device. 3. The group III nitride semiconductor light emitting device according to claim 1, wherein the sub crystal is 10% or less of the whole. 4. The group III nitride semiconductor light emitting device according to claim 1, wherein the main crystal is a boron phosphide crystal (BP). 5. The group III nitride semiconductor light-emitting device according to claim 1, wherein the main crystal is a boron-gallium phosphide crystal. 6. The group III nitride semiconductor light-emitting device according to claim 1, wherein the main crystal is a boron-phosphide-indium crystal. 7. The group III nitride semiconductor light emitting device according to claim 1, wherein said buffer layer is formed by laminating buffer layers having different proportions of main crystals. 8. The group III nitride semiconductor light emitting device according to claim 1, wherein an intervening layer is provided between the buffer layer and the light emitting portion constituting layer. 9. The group III nitride semiconductor light emitting device according to claim 8, wherein said intervening layer is a composition gradient layer. 10. The II according to claim 1, wherein the buffer layer is a low-temperature buffer layer grown at a low temperature of not less than 250 ° C. and not more than 600 ° C.
Group I nitride semiconductor light emitting device.