JP2011258988A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a semiconductor element from a group III nitride semiconductor layer exhibiting excellent crystallinity and planarity of surface when constituting a semiconductor element by using a group III nitride semiconductor layer on a silicon crystal substrate.SOLUTION: In a semiconductor element having a superlattice structure layer consisting of a silicon single crystal substrate, a silicon carbide layer provided on that substrate, a group III nitride semiconductor junction layer provided in contact with the silicon carbide layer, and a group III nitride semiconductor layer on the group III nitride semiconductor junction layer, the silicon carbide layer is a layer of nonstoichiometric composition of cubic crystal having a lattice constant of 0.436-0.460 nm and containing silicon affluently in the composition, and the group III nitride semiconductor junction layer has a composition of AlGaInNM(0≤X, Y, Z≤1, X+Y+Z=1, 0≤α<1 where M is a group V element other than nitrogen).

Description

  The present invention relates to a semiconductor element configured using a laminated structure including a silicon single crystal substrate and a group III nitride semiconductor layer formed on the substrate.

Gallium nitride (GaN), aluminum nitride (AlN), and the like are conventionally known as group III nitride semiconductors. These group III nitride semiconductor materials are used to construct semiconductor light emitting elements such as light emitting diodes (English abbreviation: LED) and laser diodes (abbreviation: LD) that emit visible light having a short wavelength such as blue or green. (For example, refer to Patent Document 1). In addition, it is used to configure electronic devices such as high-frequency transistors (for example, see Non-Patent Document 1).
A semiconductor element made of such a group III nitride semiconductor material is a sapphire (α-Al 2 O 3) bulk single crystal (for example, see Patent Document 2) or a cubic silicon carbide (SiC) bulk single crystal. A crystal is used as a substrate (see, for example, Patent Document 3). For example, an LED has been manufactured using a laminated structure including a clad layer made of a group III nitride semiconductor material and a light emitting layer on a sapphire substrate (see, for example, Patent Document 4). .
However, sapphire that is commonly used as a substrate for a group III nitride semiconductor device is electrically insulating. For example, it is not easy to obtain a group III nitride LED with high voltage resistance against static electricity or the like. There is a problem. Further, since sapphire does not have good thermal conductivity, it has been difficult to produce a low-loss field effect transistor (English abbreviation: FET) using the heat dissipation of the substrate. If a silicon carbide bulk single crystal having conductivity and excellent thermal conductivity is used as a substrate, it is convenient to construct an LED having excellent voltage resistance against static electricity or the like and an FET having excellent heat dissipation. However, a silicon carbide bulk single crystal having a reasonably large diameter for use as a substrate is expensive, which is disadvantageous in producing a general-purpose group III nitride semiconductor device for consumer use.

  On the other hand, silicon single crystals (silicon) are originally excellent in thermal conductivity and well-developed large-diameter single crystals have already been mass-produced. Therefore, it is expected that a low-cost general-purpose LED having high resistance to static electricity or the like can be put into practical use by using a highly conductive and large-diameter silicon as a substrate. Further, it is expected that a low-loss high-frequency band communication FET can be realized by using silicon having a high resistance and a high thermal conductivity as a substrate. However, the lattice constant (= a) of silicon single crystal is 0.543 nm, and the a-axis lattice constant of group III nitride semiconductors such as hexagonal GaN is 3.189３, so there is a large gap between both materials. There is a lattice mismatch. Even for cubic GaN (a = 0.451 nm), the mismatch with the silicon single crystal is large. Therefore, it has been difficult to stably form a high-quality group III nitride semiconductor layer with few crystal defects on a silicon single crystal substrate.

When providing a group III nitride semiconductor layer on a single crystal substrate having a large lattice mismatch, it is a conventional technique to provide a buffer layer for relaxing mismatch of both lattices. In the prior art, the buffer layer is made of a group III nitride semiconductor material such as AlN or GaN (see, for example, Patent Document 5). However, the lattice mismatch between the silicon single crystal and cubic or hexagonal AlN or GaN is large, and the lattice strain cannot be relaxed sufficiently. For this reason, even if an attempt is made to form a group III nitride semiconductor layer using a conventional group III nitride semiconductor material as a buffer layer, the group III nitride semiconductor layer having excellent crystallinity cannot be stably formed. It is a problem.
Further, when a group III nitride semiconductor layer is formed on a silicon single crystal as a substrate, a group III nitride semiconductor layer is formed through a thin film layer of cubic 3C-type silicon carbide (3C-SiC). The prior art to do is also known (for example, refer nonpatent literature 2). However, depending on the properties of the 3C-SiC thin film layer, the crystallinity and the like of the upper group III nitride semiconductor layer is remarkably changed. Therefore, there is a difficulty in stably forming a high-quality group III nitride semiconductor layer. is there. Even when a buffer layer made of SiC is used, the group III nitride semiconductor layer formed thereon does not necessarily have excellent surface flatness.

Japanese Patent Publication No.54-3834 JP-A-6-151963 JP-A-6-326416 JP-A-6-151966 JP-A-6-314659

MA Khan et al., Applied Physics Letters, USA, 1993, 62, 1786. T. Kikuchi et al., Journal of Crystal Growth, Netherlands, 2005, Vol.271, No.1-2, e1215-e1221

  In order to obtain a semiconductor element that has excellent electrical and electrical characteristics with excellent conductivity and heat dissipation and also has a large-diameter single crystal that has already been mass-produced using a silicon single crystal as a substrate, a lattice mismatch with the substrate is suitable. Therefore, there is a need for a buffer layer having a structure that can be relaxed to provide a high-quality group III nitride semiconductor layer. For example, when forming a group III nitride semiconductor layer on a silicon single crystal substrate, even if the SiC layer is used as a buffer layer, the SiC buffer layer having a configuration that can suitably relax the lattice mismatch between the two materials is required.

  Furthermore, in addition to using a SiC buffer layer having a structure effective for alleviating lattice mismatch, lamination on the buffer layer to provide a group III nitride semiconductor layer having excellent crystallinity and excellent surface flatness. The structure also needs to be creative. In addition, in order to manufacture a semiconductor element having excellent characteristics, a manufacturing method for stably providing the SiC buffer layer and a high-quality group III nitride semiconductor layer having excellent surface flatness is required.

That is, a substrate made of a single crystal, a silicon carbide (SiC) layer provided on the surface of the single crystal substrate, a group III nitride semiconductor junction layer provided bonded to the silicon carbide layer, and the group III A semiconductor device comprising a superlattice structure layer made of a group III nitride semiconductor provided on a nitride semiconductor layer, wherein the semiconductor device of the present invention comprises (1) a substrate made of silicon single crystal, A silicon carbide layer made of cubic silicon carbide having a non-stoichiometric composition rich in silicon and having a lattice constant exceeding 0.436 nm and 0.460 nm or less, Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M represents a Group V element other than nitrogen (N), and 0 ≦ α <1.) Group III nitride semiconductor junction layer and provided thereon And a superlattice structure layer made of a group III nitride semiconductor.

In particular, the semiconductor device according to the present invention is the semiconductor device according to the above item (1), wherein (2) the superlattice structure layer provided on the group III nitride semiconductor junction layer has a different aluminum (Al) composition. The aluminum nitride gallium (compositional formula Al _X Ga _1-X N: 0 ≦ X ≦ 1) layers are alternately stacked.

In particular, a semiconductor device according to the present invention is the semiconductor device according to the above item (2), wherein (3) a group III nitride semiconductor junction layer is formed of aluminum / gallium nitride (Al _X Ga) forming a superlattice structure layer. _1-X N: 0 ≦ X ≦ 1) layer, and an aluminum nitride / gallium layer having a smaller aluminum composition (= X) is bonded to each other.
In particular, a semiconductor element according to the present invention is the semiconductor element described in the above item (1), wherein (4) the superlattice structure layer has a gallium (Ga) composition different from that of gallium nitride indium (composition formula Ga _Q In _{1 -Q} N: 0 ≦ Q ≦ 1) layers are alternately stacked.

In particular, a semiconductor element according to the present invention is the semiconductor element described in the above item (4), wherein (5) a gallium indium nitride (Ga _Q In) layer forming a superlattice structure layer on a group III nitride semiconductor junction layer. _1-Q N: 0 ≦ Q ≦ 1) layer, and a gallium nitride / indium layer having a larger gallium composition (= Q) is bonded to each other.

  In particular, a semiconductor device according to the present invention is the semiconductor device according to any one of the above items (1) to (5), wherein (6) the group III nitride semiconductor superlattice structure layer has a thickness of 5 ML. It is characterized by being composed of a group III nitride semiconductor layer of 30 ML as described above.

  In particular, a semiconductor element according to the present invention is the semiconductor element according to any one of the above items (1) to (6), wherein (7) the substrate has {111} silicon whose surface is a {111} crystal plane. It is a single crystal, and the group III nitride semiconductor junction layer is characterized by being composed of hexagonal wurtzite crystal-type nitrided AlN.

  In particular, a semiconductor element according to the present invention is the semiconductor element according to any one of (1) to (6) above, wherein (8) the substrate has {001} silicon whose surface is a {001} crystal plane. It is a single crystal and the group III nitride semiconductor junction layer is characterized by being composed of cubic zinc blende crystal type aluminum nitride (AlN).

  A silicon single crystal substrate; a silicon carbide layer provided on the surface of the silicon single crystal substrate; a group III nitride semiconductor junction layer provided bonded to the silicon carbide layer; and group III nitride And a superlattice structure layer made of a group III nitride semiconductor provided on the oxide semiconductor layer. The method for manufacturing a semiconductor element of the present invention includes (A) (1) silicon single A step of spraying hydrocarbon gas on the surface of the crystal substrate to adsorb hydrocarbons on the crystal surface forming the surface of the substrate; and (2) thereafter heating the silicon single crystal substrate to a temperature higher than the adsorbed temperature. Forming a cubic silicon carbide layer having a non-stoichiometric composition rich in silicon and having a lattice constant greater than 0.36 nm and less than 0.460 nm on the surface of a silicon single crystal substrate; (3) Then, the surface of the silicon carbide layer Supplying a gas containing a Group V element and a gas containing a Group III element to form a Group III nitride semiconductor junction layer; and (4) Thereafter, on the Group III nitride semiconductor junction layer, And a step of forming a superlattice structure layer made of a group III nitride semiconductor.

  In particular, the method of manufacturing a semiconductor device of the present invention is the manufacturing method described in the above section (A), wherein (B) the substrate is a {111} silicon single crystal having a {111} crystal plane as its surface, After forming a cubic silicon carbide layer having a non-stoichiometric composition rich in silicon and having a {111} crystal plane on the surface of the substrate, the silicon carbide layer Forming a hexagonal group III nitride semiconductor junction layer on the surface, and then forming a superlattice structure layer made of a hexagonal group III nitride semiconductor on the group III nitride semiconductor junction layer. It is a feature.

  Further, in particular, in the manufacturing method described in the above item (A), (C) the substrate is a {001} silicon single crystal having a {001} crystal plane as a surface, and a compositional silicon is formed on the surface of the substrate. After forming a cubic silicon carbide layer having a non-stoichiometric composition richly containing and having a {001} crystal plane as a surface, a cubic group III is formed on the surface of the silicon carbide layer. A nitride semiconductor junction layer is formed, and then a superlattice structure layer made of a cubic group III nitride semiconductor is formed on the group III nitride semiconductor junction layer.

  In particular, in the manufacturing method described in the above item (B) or (C), (D) a non-stoichiometric composition containing silicon in a compositionally rich manner on the surface of a substrate made of a silicon single crystal. After forming the silicon carbide layer, supplying a gaseous material containing aluminum and a gaseous material containing nitrogen to the surface of the silicon carbide layer to form a group III nitride semiconductor junction layer made of aluminum nitride It is characterized by.

  In particular, in the manufacturing method described in the above section (D), (E) a silicon carbide layer having a non-stoichiometric composition containing silicon in a compositionally rich manner is formed on the surface of a substrate made of a silicon single crystal. After forming, a gas source containing aluminum is supplied to the surface of the silicon carbide layer, an aluminum film is deposited, a gas source containing nitrogen is supplied, the aluminum film is nitrided, and an aluminum nitride layer It is characterized by forming.

  Further, in particular, in the manufacturing method described in the above item (D), (F) while spraying hydrocarbon gas on the surface of the substrate made of silicon single crystal and irradiating electrons, the surface of the silicon single crystal substrate is It is characterized by adsorbing silicon carbide.

  In particular, in the manufacturing method described in the above item (F), (G) a temperature at which hydrocarbons are adsorbed while irradiating electrons after adsorbing hydrocarbons on the surface of a substrate made of a silicon single crystal. The silicon single crystal substrate is heated to the above temperature so that the surface of the silicon single crystal substrate has a lattice constant of more than 0.436 nm and not more than 0.460 nm. The cubic silicon carbide layer is formed.

That is, the present invention relates to the following.
[1] A silicon single crystal substrate, a silicon carbide layer provided on the surface of the substrate, a group III nitride semiconductor junction layer provided in contact with the silicon carbide layer, and a group III nitride semiconductor junction layer on the group III nitride semiconductor junction layer A semiconductor element including a superlattice structure layer made of a group nitride semiconductor, wherein the silicon carbide layer is cubic and has a lattice constant of more than 0.436 nm and not more than 0.460 nm, and is a non-rich silicon composition The group III nitride semiconductor junction layer has a composition of Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1, 0). ≦ α <1, and M is a group V element other than nitrogen.)
[2] A layer in which a superlattice structure layer made of a group III nitride semiconductor is formed by alternately laminating aluminum nitride gallium (Al _X Ga _1-X N: 0 ≦ X ≦ 1) layers having different aluminum (Al) compositions The semiconductor element according to [1], wherein
[3] The semiconductor element according to [2], wherein the aluminum nitride / gallium layer having a different aluminum composition and having a small aluminum composition is in contact with the group III nitride semiconductor junction layer.
[4] A layer in which a superlattice structure layer made of a group III nitride semiconductor is formed by alternately laminating gallium nitride indium (Ga _Q In _{1 -Q} N: 0 ≦ Q ≦ 1) layers having different gallium (Ga) compositions [5] The gallium nitride / indium layer having a different gallium composition and a layer having a larger gallium composition is in contact with the group III nitride semiconductor junction layer. The semiconductor element according to [4], which is characterized in that
[6] Any one of [1] to [5], wherein the superlattice structure layer made of a group III nitride semiconductor has a thickness in a range of 5 monolayers (ML) to 30 ML. The semiconductor element as described in.
[7] The silicon single crystal substrate is a substrate having a {111} crystal surface, and the group III nitride semiconductor junction layer is a hexagonal wurtzite crystal aluminum nitride (AlN) layer. The semiconductor element according to any one of [1] to [6].
[8] The silicon single crystal substrate is a substrate having a {001} crystal surface, and the group III nitride semiconductor junction layer is a cubic zinc blende crystal type aluminum nitride (AlN) layer. The semiconductor element according to any one of [1] to [6], which is characterized.

[9] (1) A step of spraying hydrocarbon gas on the surface of the silicon single crystal substrate to adsorb hydrocarbons on the surface of the substrate, and (2) heating the silicon single crystal substrate to a temperature higher than the adsorbed temperature. And forming a cubic silicon carbide layer having a non-stoichiometric composition rich in silicon and having a lattice constant exceeding 0.436 nm and not more than 0.460 nm on the surface of the silicon single crystal substrate. And (3) supplying a gas containing a group V element and a gas containing a group III element to the surface of the silicon carbide layer to form a group III nitride semiconductor junction layer, and (4) III And a step of forming a superlattice structure layer made of a group III nitride semiconductor on the group nitride semiconductor bonding layer in this order.
[10] A silicon single crystal substrate is a substrate having a {111} crystal plane on the surface, a silicon carbide layer formed on the substrate surface is a layer having a {111} crystal plane, and a group III nitride semiconductor junction layer 10. The method of manufacturing a semiconductor device according to claim 9, wherein a hexagonal crystal layer is used, and a superlattice structure layer made of a group III nitride semiconductor is a hexagonal crystal layer.
[11] A silicon single crystal substrate is a substrate whose surface is a {001} crystal plane, a silicon carbide layer formed on the substrate surface is a layer whose surface is a {001} crystal plane, and a group III nitride semiconductor junction layer 10. The method of manufacturing a semiconductor device according to claim 9, wherein a superlattice structure layer made of a group III nitride semiconductor is a cubic layer.
[12] In the step of (3), a gas containing aluminum as a gas containing a group III element and a raw material containing nitrogen as a gas containing a group V element are supplied to the surface of the silicon carbide layer, and nitriding The method for manufacturing a semiconductor device according to any one of [9] to [11], wherein a group III nitride semiconductor bonding layer made of aluminum is formed.
[13] The step (3) includes (3a) a step of supplying a gas containing a group III element to the surface of the silicon carbide layer to form a layer containing a group III element, and (3b) a group III The method according to any one of [9] to [12], wherein the step includes nitriding a layer including an element to form a nitride layer of a group III element as a group III nitride semiconductor bonding layer A method for manufacturing a semiconductor device.
[14] The semiconductor according to [13], wherein in the step (3a), a gas containing aluminum as a gas containing a Group III element is supplied to the surface of the silicon carbide layer to form an aluminum layer. Device manufacturing method.
[15] The step (1) is characterized in that (1a) a step of blowing hydrocarbon gas onto the surface of the silicon single crystal substrate and irradiating the surface of the substrate with electrons to adsorb the hydrocarbon onto the surface of the substrate. [9] The method for manufacturing a semiconductor device according to any one of [14].
[16] In steps (1) and (2), (1b) the surface of the silicon single crystal substrate is adsorbed with hydrocarbons, and then irradiated with electrons, to a temperature equal to or higher than the temperature at which the hydrocarbons were adsorbed. A silicon single crystal substrate is heated, and the surface of the silicon single crystal substrate has a lattice constant of 0.436 nm or more and 0.460 nm or less. The method for manufacturing a semiconductor element according to any one of [9] to [14], wherein the silicon carbide layer is formed.

According to the present invention, a substrate made of a single crystal, a silicon carbide layer provided on the surface of the single crystal substrate, a group III nitride semiconductor junction layer provided bonded to the silicon carbide layer, and A semiconductor device comprising a superlattice structure layer made of a group III nitride semiconductor provided on a group III nitride semiconductor layer, wherein the semiconductor device of the present invention comprises: (1) a substrate made of silicon single crystal, A buffer layer is formed from cubic silicon carbide having a non-stoichiometric composition rich in silicon and having a lattice constant of 0.436 nm or more and 0.460 nm or less provided on the substrate, On the buffer layer, Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M represents a Group V element other than nitrogen (N), A group III nitride semiconductor junction layer comprising: 0 ≦ α <1) In addition, since the semiconductor element is obtained by using a laminated structure in which a superlattice structure layer made of a group III nitride semiconductor is provided on the group III nitride semiconductor bonding layer, the crystal element has high quality, Thus, a group III nitride semiconductor layer having excellent surface flatness can be provided, and thus a high-performance semiconductor device can be provided.

In particular, in the present invention, the superlattice structure layer provided on the group III nitride semiconductor junction layer is formed by alternately laminating Al _X Ga _1-X N (0 ≦ X ≦ 1) layers having different aluminum compositions. As a result, it is possible to stably provide a group III nitride semiconductor layer having excellent crystallinity and excellent surface flatness, and is therefore effective in stably providing high-performance semiconductor elements. Play.

In particular, also in the present invention, in the provision of the superlattice structure layer composed of _{Al X Ga 1-X N (} 0 ≦ X ≦ 1) layer different aluminum composition, _Al X Ga ₁ to constitute a superlattice structure layer among _{-X N (0 ≦ X ≦ 1} ) layer, laminated structure provided by the _{Al X Ga 1-X} N layer to a smaller aluminum composition (= X) is joined to a group III nitride semiconductor junction layer Therefore, in particular, a group III nitride semiconductor layer having excellent surface flatness can be formed, which can contribute to obtaining a semiconductor device having a configuration capability.

In the present invention, the superlattice structure layer provided on the group III nitride semiconductor junction layer is alternately laminated with Ga _Q In _1-Q N (0 ≦ Q ≦ 1) layers having different gallium (Ga) compositions. Therefore, it is possible to stably provide a group III nitride semiconductor layer having excellent crystallinity and excellent surface flatness, and thus stably producing a high-performance semiconductor element. It is effective to provide.
In particular, the present _invention, in the provision of the superlattice structure layer composed of _{Ga Q In 1-Q N (} 0 ≦ Q ≦ 1) _{layer, Ga Q In 1-Q N} (0 ≦ forming the superlattice structure layer In Q ≦ 1), since the gallium nitride / indium layer having a larger gallium composition (= Q) is bonded on the group III nitride semiconductor bonding layer, the surface flatness is particularly improved. A group III nitride semiconductor layer having excellent resistance can be formed, which can contribute to obtaining a high-performance semiconductor element.

In particular, in the present invention, the superlattice structure layer is an Al _X Ga _1-X N (0 ≦ X ≦ 1) layer or Ga _Q In _1-Q N (0 ≦ Q ≦ 1) having a thickness of 5 ML or more and 30 ML. Since the layer is composed of layers, in particular, a group III nitride semiconductor layer having excellent surface flatness can be stably formed, which can contribute to stably obtaining a high-performance semiconductor element.

In particular, in the present invention, the substrate is made of {111} silicon single crystal, and the group III nitride semiconductor junction layer provided on the substrate surface via the SiC buffer layer is formed as a hexagonal wurtzite crystal type Al _X Ga _Y. In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M represents a group V element other than nitrogen (N), and 0 ≦ α <1). Therefore, the superlattice structure layer and the like provided thereon can be unified from the hexagonal group III nitride semiconductor layer, and thus the characteristics based on the hexagonal group III nitride semiconductor material can be obtained. This is advantageous for obtaining a semiconductor device that can be developed.

In particular, in the present invention, a {001} silicon single crystal whose surface is a {001} crystal plane is used as a substrate, and a group III nitride semiconductor junction layer provided on the substrate surface via a SiC buffer layer is formed of cubic crystal. Sphalerite crystal type Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M represents a group V element other than nitrogen (N), 0 ≦ α <1)), the superlattice structure layer and the like provided thereon can be unified from a cubic group III nitride semiconductor layer, and therefore cubic cubic layers can be formed. This is advantageous for obtaining a semiconductor element capable of exhibiting characteristics based on a group III nitride semiconductor material.

Further, in the present invention, a substrate made of a silicon single crystal, a silicon carbide layer provided on the surface of the silicon single crystal substrate, a group III nitride semiconductor bonding layer provided to be bonded to the silicon carbide layer, When manufacturing a semiconductor device having a superlattice structure layer made of a group III nitride semiconductor provided on the group III nitride semiconductor layer, a hydrocarbon gas is blown onto the surface of the single crystal substrate to Since the silicon single crystal substrate is heated to a temperature higher than the adsorbed temperature to form a silicon carbide layer by adsorbing hydrocarbons on the crystal planes forming, the lattice is formed on the surface of the silicon single crystal substrate. It is possible to reliably form a cubic crystal having a non-stoichiometric composition rich in silicon and having a constant exceeding 0.436 nm and not more than 0.460 nm. a _Al X _Ga Y In _{N 1-α M α (0} ≦ X, Y, Z ≦ 1, X + Y + Z = 1. M represents a Group V element other than nitrogen (N), and 0 ≦ α <1.) III Group consisting of Since a nitride semiconductor junction layer and a superlattice structure layer made of a group III nitride semiconductor can be formed on the nitride semiconductor junction layer, a semiconductor device having excellent characteristics reflecting the good crystallinity of these semiconductor layers. Can be manufactured.

In particular, according to the present invention, a {111} silicon single crystal having a {111} crystal plane as a surface is used as a substrate, and the surface of the substrate is non-stoichiometrically compositionally rich in silicon. And a cubic {111} silicon carbide layer having a {111} crystal plane as a surface is formed, and a hexagonal Al _X Ga _Y In _Z N _1-α is formed on the surface of the silicon carbide layer. Group III nitride semiconductor junction made of M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M represents a Group V element other than nitrogen (N) and 0 ≦ α <1). After forming a layer and then forming a superlattice structure layer made of a hexagonal group III nitride semiconductor on the group III nitride semiconductor junction layer, a semiconductor element is formed. Appropriate expression of optical or electrical properties based on the crystal properties of Group III nitride semiconductors Can be manufactured.

  In particular, according to the present invention, a {001} silicon single crystal having a {001} crystal plane as a surface is used as a substrate, and the surface of the substrate is non-stoichiometrically rich in composition. Forming a cubic silicon carbide layer having a composition and having a {001} crystal plane as a surface, and forming a cubic group III nitride semiconductor junction layer on the surface of the silicon carbide layer; Since the semiconductor element is formed through the step of forming a superlattice structure layer made of a cubic group III nitride semiconductor on the group III nitride semiconductor junction layer, the cubic group III nitride semiconductor is formed. Thus, it is possible to manufacture a semiconductor element that can preferably exhibit optical or electrical characteristics based on the crystal characteristics.

  In particular, according to the present invention, after a silicon carbide layer having a non-stoichiometric composition containing silicon in a composition is formed on the surface of a substrate made of a silicon single crystal, the surface of the silicon carbide layer is formed. In addition, by supplying a gaseous material containing aluminum and a gaseous material containing nitrogen to form a group III nitride semiconductor junction layer made of aluminum nitride, lattice mismatch can be reduced, and therefore high-quality AlN A high-performance semiconductor element having a group III nitride semiconductor junction layer made of can be manufactured.

  In particular, according to the present invention, after a silicon carbide layer having a non-stoichiometric composition containing silicon in a composition is formed on the surface of a substrate made of a silicon single crystal, the surface of the silicon carbide layer is formed. In forming a group III nitride semiconductor junction layer made of AlN, a gaseous material containing aluminum is supplied, an aluminum film is formed on the surface of the silicon carbide layer, and then a gaseous material containing nitrogen is supplied to the film. Since the aluminum film is nitrided to form the aluminum nitride layer, for example, a group III nitride semiconductor junction layer can be formed from AlN having a uniform crystal system of hexagonal crystal.

  In particular, according to the present invention, the surface of the silicon single crystal substrate is irradiated with electrons while the hydrocarbon gas is blown onto the surface of the substrate made of the silicon single crystal. Through a step of adsorbing silicon carbide, a cubic silicon carbide layer having a non-stoichiometric composition rich in silicon and having a lattice constant exceeding 0.436 nm and not exceeding 0.460 nm is formed. Therefore, it is possible to stably form a silicon carbide layer with particularly few crystal defects and excellent crystallinity, and thus a high-performance semiconductor element can be stably manufactured.

  In particular, according to the present invention, the hydrocarbon gas is adsorbed on the surface of the substrate made of silicon single crystal while irradiating with the hydrocarbon gas, and then the hydrocarbon is irradiated with the electron. The silicon single crystal substrate is heated to a temperature equal to or higher than the temperature at which the silicon is adsorbed to promote a chemical reaction between silicon forming the substrate and hydrocarbon adsorbed on the surface of the substrate, and a cubic silicon carbide layer is formed. Since it is formed, a cubic silicon carbide layer with few crystal defects can be efficiently formed, and thus a high-performance semiconductor element can be efficiently manufactured.

It is a plane schematic diagram of LED as described in Example 1 of this invention. It is a schematic diagram which shows the cross-section along the broken line AA of LED described in FIG. It is a cross-sectional schematic diagram of LED as described in Example 2 of this invention.

  As a silicon single crystal substrate, a silicon single crystal having a crystal plane of various plane orientations as a surface can be used. However, in the practice of the present invention, a silicon crystal that can be most suitably used as a substrate has a surface of {001}. It is a {001} or {111} single crystal with a crystal plane or {111} crystal plane. A silicon single crystal having a crystal plane inclined from these crystal planes as a surface can be sufficiently used as a substrate. A silicon single crystal substrate having a crystal plane inclined at an angle from the {001} crystal plane and an angle, for example, a crystal plane inclined in the 2 ° <110> direction, has an antiphase (antiphase) grain boundary (abbreviation: (APD) (Koji Saka, Material Science Series "Crystal Electron Microscopy-For Materials Researchers", November 25, 1997, published by Uchida Otsukuru, 1st Edition, pp. 64-65 This is advantageous for obtaining a crystal layer with a small number of references). In the present invention, {001} silicon single crystal is mainly used when a semiconductor element using a cubic crystal layer is formed. On the other hand, the {111} silicon single crystal is mainly used when a semiconductor element using a hexagonal crystal layer is formed.

The conductivity type of the silicon single crystal used as the substrate is not limited. A p-type or n-type conductivity silicon single crystal can be used as the substrate. In particular, a highly conductive silicon single crystal substrate having a low resistivity (specific resistance) can be suitably used for manufacturing semiconductor light emitting devices such as LEDs and LDs. In addition, the high-resistance silicon single crystal can be used as a substrate for a semiconductor device that needs to reduce leakage of a current for operating the device (device operating current) to the substrate side. For example, it can be suitably used as a substrate for manufacturing an FET (a high-resistance p-type or n-type semiconductor may be referred to as a π-type or a ν-type, respectively, by Hiroo Yonezu, “Optical Communication Device Engineering”). "Light-emitting / light-receiving element", published on May 20, 1995, Engineering Book Co., Ltd., 5th edition, page 317, footnote)).
In the present invention, a silicon carbide layer is provided on the surface regardless of the orientation of the crystal plane forming the surface of the silicon single crystal used as the substrate. This silicon carbide layer is produced according to Ramsdel's notation (edited by the Japan Society for the Promotion of Science High Temperature Ceramic Materials 124th Committee, “New SiC-Based Ceramic Materials-Recent Developments”, February 28, 2001, Co., Ltd.) (See Uchida Otsukuru, first edition, pages 13 to 16), and most preferably a cubic crystal layer having a 3C type crystal structure. Whether it is a 3C type cubic silicon carbide (3C-SiC) layer or a 4H-type or 6H-type hexagonal silicon carbide (4H-SiC, 6H-SiC) layer, for example, This can be judged by analyzing the electron diffraction image.

The 3C—SiC layer is desirably formed using hydrocarbon adsorbed on the surface of the silicon single crystal substrate. Examples of hydrocarbon gas for adsorbing hydrocarbons include saturated aliphatic hydrocarbons such as methane (molecular formula CH ₃ ), ethane (molecular formula C ₂ H ₆ ) and propane (molecular formula C ₃ H ₈ ), and acetylene (molecular formula C An unsaturated hydrocarbon such as ₂ H ₂ ) can be exemplified. In addition, although there are aromatic hydrocarbons or alicyclic hydrocarbons, acetylene which is easily decomposed and reacts with silicon is most preferably used. The temperature for adsorbing acetylene on the {111} crystal plane of the {111} silicon single crystal is preferably 400 ° C. to 600 ° C. The temperature suitable for adsorbing acetylene on the {001} crystal plane of the {001} silicon single crystal is higher than that of the {111} crystal plane and is 450 ° C. to 650 ° C.

Hydrocarbons such as acetylene are preferably adsorbed after creating the most aligned structure of silicon atoms on the crystal plane forming the surface of the silicon single crystal substrate. For example, it is preferable to adsorb silicon carbide after a (7 × 7) rearrangement structure appears on the surface of {111} silicon single crystal substrate made of {111} crystal planes. The (7 × 7) rearrangement structure is, for example, a {111} crystal plane forming the surface of a {111} silicon single crystal in a high vacuum environment of about 10 ⁻⁶ parcal (pressure unit: Pa), for example, a molecular beam It can be formed by performing heat treatment at 750 ° C. to 850 ° C. in an epitaxial (abbreviation: MBE) growth chamber. The rearrangement structure on the surface of the silicon single crystal substrate can be confirmed by electron diffraction analysis means such as high-speed reflection electron diffraction (abbreviation: RHEED).

  After the hydrocarbon is adsorbed on the crystal plane forming the surface of the silicon single crystal substrate, the silicon single crystal substrate is heated to cause the adsorbed hydrocarbon to react with the silicon atoms forming the substrate crystal. Form. At this time, when the silicon single crystal substrate is heated at a relatively high temperature, a silicon carbide layer rich in silicon stoichiometrically can be formed. The silicon single crystal substrate on which the hydrocarbon is adsorbed is formed by heating at 500 ° C. to 700 ° C., for example. As the temperature for heating is increased, a silicon carbide layer containing abundant silicon stoichiometrically can be formed in a short time. The degree of richness of silicon is reflected in the lattice constant of silicon carbide having a non-stoichiometric composition forming the silicon carbide layer. In silicon carbide having a non-stoichiometric composition, the lattice constant increases as the silicon composition increases. Whereas the lattice constant of 3C-SiC having an equivalent composition is 0.436 nm (see the above-mentioned “New SiC-Based Ceramic Materials—Recent Developments”, page 340, Table 5.1.1.) The non-stoichiometric silicon carbide layer according to the invention is characterized by having a lattice constant of more than 0.436 nm and not more than 0.460 nm.

The cubic 3C-type silicon carbide layer having a lattice constant in the above range has a small degree of lattice mismatch with the group III nitride semiconductor material constituting the group III nitride semiconductor junction layer. Therefore, for example, when forming a group III nitride semiconductor junction layer from cubic zinc blende crystal type GaN having a lattice constant of 0.451 nm, it is useful as a buffer layer having excellent lattice matching.
In addition, since the spacing of the (110) crystal plane of the cubic 3C-type silicon carbide layer having the lattice constant in the above-described range substantially coincides with the a axis of the wurtzite crystal type hexagonal AlN, III It is also convenient to form a hexagonal group III nitride semiconductor layer as a group nitride semiconductor junction layer. A cubic silicon carbide layer having a lattice constant outside the above range has an increased lattice mismatch with either a cubic or hexagonal crystal group III nitride semiconductor material. The crystal quality of the group nitride semiconductor junction layer is significantly deteriorated, which is extremely inconvenient.

A silicon carbide layer with a non-stoichiometric composition that contains silicon more abundantly than carbon also adsorbs hydrocarbons to the surface of a silicon single crystal substrate, and then supplies a gas containing silicon to the surface of the substrate. However, it can also be formed by heating. For example, it is formed by heating the surface of a silicon single crystal substrate on which hydrocarbons are adsorbed while supplying silane (molecular formula SiH ₄ ). Further, for example, it can be formed by heating a silicon single crystal substrate on which hydrocarbons are adsorbed while irradiating a silicon beam in an MBE growth chamber held in a high vacuum. The lattice constant of the formed silicon carbide layer having a non-stoichiometric composition can be measured by an analysis means such as an electron diffraction method.

  In forming a silicon carbide layer having a non-stoichiometric composition, in order to obtain a silicon carbide layer having a {001} crystal plane as a surface, a {001} silicon single crystal having a {001} crystal plane as a surface Is used as a substrate. In addition, in order to obtain a silicon carbide layer having a non-stoichiometric composition having a {111} crystal plane as a surface, a {111} silicon single crystal having a {111} crystal plane as a surface is used as a substrate.

When forming a silicon carbide layer on the surface of a silicon single crystal substrate regardless of the plane orientation of the crystal plane forming the surface, if hydrocarbon gas is blown onto the surface of the substrate while irradiating electrons, It is adsorbed uniformly on the surface. As the electrons to be irradiated, for example, thermal electrons emitted from a metal heated in a vacuum are used. Irradiate with uniform density on the surface of the silicon single crystal substrate. As the irradiation density, 1 × 10 ^{12 to} 5 × 10 ¹³ cm ⁻² is suitable. If the acceleration energy of the irradiated electrons is as low as less than about 100 electron volts (unit: eV), the hydrocarbons cannot be uniformly adsorbed on the surface of the silicon single crystal substrate. Irradiation of electrons with acceleration energy exceeding 500 eV is disadvantageous because the decomposition and desorption of hydrocarbons are accelerated.
Therefore, the potential difference between an electron generation source, for example, a tungsten (W) filament and the silicon single crystal substrate of the irradiated object is preferably 100 V (V) or more and 500 V or less.

In addition, when a silicon single crystal substrate having hydrocarbons adsorbed on the surface is heated to form a 3C-SiC layer on the surface of the substrate, if electrons are irradiated, crystal defects such as twins and stacking faults A 3C—SiC layer having low density and excellent crystallinity can be formed. As the electron irradiation density, 1 × 10 ^{12 to} 5 × 10 ¹³ cm ⁻² is suitable. Further, the acceleration energy of the irradiated electrons is suitably 100 eV to 500 eV.

The silicon carbide layer having a non-stoichiometric composition includes Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1. Symbol M is other than nitrogen (N). A Group III nitride semiconductor layer composed of a Group V element, where 0 ≦ α <1, is provided by bonding. Al _X Ga _Y In _{ZN 1-α} M _α forming the group III nitride semiconductor junction layer is, for example, aluminum nitride gallium (Al _X Ga _Y N: 0 ≦ X, Y ≦ 1, X + Y = 1), nitriding It can be composed of gallium indium (Ga _Y In _Z N: 0 ≦ Y, Z ≦ 1, Y + Z = 1), aluminum nitride phosphide (AlN _1−α P _α : 0 ≦ α <1).

  The group III nitride semiconductor junction layer has a lattice constant or lattice spacing that approximates the lattice constant (a) (greater than 0.436 nm and less than or equal to 0.460 nm) of a non-stoichiometric silicon carbide layer. It is preferable to comprise a group III nitride semiconductor material having For example, it can be suitably configured from cubic zinc blende crystal type AlN (a = 0.438 nm) or GaN (a = 0.451 nm). Further, a hexagonal wurtzite crystal type having an a axis approximating the (110) crystal plane interval (0.308 nm to 0.325 nm) of the cubic silicon carbide layer having a non-stoichiometric composition according to the present invention. It can be composed of AlN, GaN and mixed crystals thereof.

  In order to form a group III nitride semiconductor junction layer made of hexagonal AlN or the like, it is advantageous to use a {111} silicon single crystal having a {111} crystal plane as the surface. Further, in order to obtain a group III nitride semiconductor junction layer made of cubic AlN or the like, it is convenient to use a {001} silicon single crystal having a {001} crystal plane as a substrate.

  Furthermore, when forming a group III nitride semiconductor layer made of AlN, an aluminum (Al) film is once deposited on the surface of a silicon single crystal substrate, and then the Al film is placed in an atmosphere containing a nitrogen-containing gas. There is also means for nitriding to form an AlN layer. According to this forming means, an AlN layer having a uniform crystal system can be formed efficiently. For example, if an Al film is formed on the surface of the {111} silicon single crystal substrate made of the {111} crystal plane and then nitrided in, for example, a nitrogen plasma atmosphere, the crystal system is uniformly arranged in a hexagonal system. A hexagonal AlN layer can be formed.

  The group III nitride semiconductor bonding layer formed with good consistency on the non-stoichiometric silicon carbide layer promotes the formation of a superlattice structure layer provided thereon. The group III nitride semiconductor junction layer is formed by, for example, metal organic chemical vapor deposition (abbreviation: MOCVD), halogen or hydride chemical vapor deposition (CVD), MBE, chemical beam. It can be formed using growth means such as a growth method (English abbreviation: CBE).

A superlattice structure layer made of a group III nitride semiconductor is formed on the group III nitride semiconductor junction layer. For example, group III nitride semiconductor layers having different constituent element compositions are alternately stacked to form a superlattice structure. In addition, for example, a superlattice structure is formed by alternately laminating group III nitride semiconductor layers having different band gaps. When the group III nitride semiconductor junction layer is composed of AlN or GaN, the superlattice structure layer has Al _X Ga _1-X N (0 ≦ X ≦) having a different aluminum composition (= X) due to good lattice matching. 1) It is preferable to comprise from a layer. Further preferably constructed from _{Ga Q In 1-Q N (} 0 ≦ Q ≦ 1) layer different gallium composition (= Q).

In particular, in the _{Al X Ga 1-X} N layer different aluminum composition constituting the superlattice structure layer, an _{Al X Ga 1-X} N layer to the aluminum composition minimized, the Group III nitride semiconductor junction layer When it is configured to be bonded, a superlattice structure layer that provides a group III nitride semiconductor layer having excellent surface flatness can be obtained. Similarly, in the _{Ga Q In 1-Q N (} 0 ≦ Q ≦ 1) layer different gallium composition constituting the superlattice structure layer, _{Ga Q In 1-Q} N layer to maximize the gallium composition of If it is configured to be bonded to the group III nitride semiconductor bonding layer, a superlattice structure layer that provides a group III nitride semiconductor layer having excellent surface flatness can be obtained.

In particular, when the superlattice structure layer is composed of an Al _X Ga _1-X N layer or a Ga _Q In _1-Q N layer having a layer thickness of 5 ML or more and 30 ML or less, the propagation of strain inside the crystal layer is advantageously performed. Can be suppressed. Therefore, it is possible to form a superlattice structure layer that provides a group III nitride semiconductor layer having excellent surface flatness. The thickness of 1 ML is 1/2 the thickness of the c-axis in a hexagonal group III nitride semiconductor layer. For example, the 1 ML thickness of hexagonal wurtzite crystal type GaN having a c-axis of 0.520 nm is 0.260 nm. The cubic group III nitride semiconductor layer has a thickness corresponding to the lattice constant.

The superlattice structure layer may also be a quantum well structure that gives a quantum level to electrons and holes. When a quantum well structure is composed of Al _X Ga _1-X N (0 ≦ X ≦ 1) layers, the Al _X Ga _1-X N layer having a larger aluminum composition (= X) and a larger forbidden band width is blocked. As the (barrier) layer, an Al _x Ga _1-x N layer having a smaller aluminum composition (= X) and a smaller forbidden band width is formed as a well layer. Further, when a quantum well structure is formed from Ga _Q In _{1 -Q} N (0 ≦ Q ≦ 1) layers, a Ga _Q In _{1 -Q} N layer having a larger gallium composition (= Q) and a larger forbidden band width. And a Ga _Q In _{1 -Q} N layer having a smaller gallium composition (= Q) and a smaller forbidden band width as a well layer.

The Al _X Ga _1-X N layer or the Ga _Q In _1-Q N layer constituting the superlattice structure layer is, for example, the MOCVD method, halogen or the same as in the case of the group III nitride semiconductor junction layer described above. It can be formed using growth means such as hydride CVD, MBE, CBE. If a superlattice structure layer is subsequently formed on the group III nitride semiconductor junction layer according to the same growth means used for the formation of the group III nitride semiconductor junction layer, it is easy to obtain a semiconductor device. It becomes.

When the Al _X Ga _1-X N layer or Ga _Q In _1-Q N layer constituting the superlattice structure layer is grown, the group III element raw material and the group V element constituting the layer are alternately and repeatedly supplied. Thus, a superlattice structure layer having excellent surface flatness can be obtained. For example, means for supplying a group III element material first to the surface of the group III nitride semiconductor junction layer, then stopping the group III element material supply, and supplying a nitrogen source instead, ie, a group III element If an Al _X Ga _1-X N layer or Ga _Q In _1-Q N layer formed while alternately supplying elements and Group V materials is used, a superlattice structure with excellent surface flatness can be formed.

Cleaning the surface of a silicon single crystal substrate, adsorbing hydrocarbons on the cleaned substrate surface, forming a silicon carbide layer using the adsorbed hydrocarbons, and a group III nitride semiconductor junction on the silicon carbide layer For the formation of the layer and the formation of the superlattice structure layer on the group III nitride semiconductor junction layer, it is a good idea to manufacture the semiconductor device easily with a simple process, by performing the same equipment consistently. .
According to the MBE method, since the growth is performed in a high vacuum environment, when hydrocarbons are adsorbed and a silicon carbide layer is formed based on the hydrocarbons, electrons are irradiated toward the surface of the silicon single crystal substrate. It is also easy to do. Further, in the MBE method, as described above, it is possible to easily form the Al _X Ga _1-X N layer or the Ga _Q In _1-Q N layer forming the superlattice structure layer while alternately supplying the constituent element materials. There is.

  A growth layer having excellent surface flatness can be formed on the superlattice structure layer. Therefore, if such a growth layer having excellent flatness is used as an active layer (active layer), a semiconductor element having excellent optical or electrical characteristics can be configured. For example, a hexagonal group III nitride semiconductor layer provided in a superlattice structure layer made of a hexagonal group III nitride semiconductor layer on a hexagonal group III nitride semiconductor junction layer is formed of an electron transit layer (channel). ) Layer) or an electron supply layer, a high mobility FET can be constructed. In particular, a high mobility FET including an electron transit layer that efficiently accumulates two-dimensional electrons can be manufactured due to the expression of piezo due to a hexagonal group III nitride semiconductor.

  In addition, for example, a cubic group III nitride semiconductor layer provided in a superlattice structure layer made of a cubic group III nitride semiconductor layer on a cubic group III nitride semiconductor junction layer may be used as a lower cladding layer or a light emitting layer. When used as a layer, a light-emitting element such as a high-luminance LED can be formed. In particular, by utilizing the properties of a cubic group III nitride semiconductor in which the valence band is degenerated, an LD with a uniform oscillation wavelength can be provided.

Example 1
In Example 1, a silicon carbide layer having a non-stoichiometric composition provided on a (111) silicon single crystal substrate having a (111) crystal plane as a surface, a hexagonal group III nitride semiconductor junction layer, and a hexagonal crystal The present invention will be specifically described by taking as an example a case where a light emitting diode (LED) is manufactured from an epitaxial multilayer structure including a superlattice structure layer made of a group III nitride semiconductor layer.

  A planar structure of the semiconductor LED 10 fabricated in Example 1 is schematically shown in FIG. FIG. 2 schematically shows a cross-sectional structure along the broken line AA of the LED 10 shown in FIG.

In manufacturing the LED 10, a p-type silicon single crystal having boron (element symbol: B) and having a (111) crystal plane as the surface was used as the substrate 101. After the substrate 101 was transferred into a growth chamber for MBE growth, the substrate 101 was heated to 850 ° C. in a high vacuum of about 5 × 10 ⁻⁷ Pascal (Pa). While monitoring the RHEED pattern, heating was continued at the same temperature until the (111) crystal plane forming the surface of the substrate 101 had a (7 × 7) rearrangement structure.

  After confirming the appearance of the (7 × 7) rearrangement structure, the temperature was lowered to 450 ° C. while the substrate 101 was housed in the MBE growth chamber. Next, acetylene gas was sprayed onto the surface of the substrate 101 to adsorb acetylene on the surface. The acetylene gas was continuously blown on the RHEED pattern until the electron diffraction spots caused by the (7 × 7) rearrangement structure on the surface of the substrate 101 almost disappeared.

  Thereafter, the blowing of acetylene gas to the surface of the substrate 101 was stopped, and the temperature of the substrate 101 was raised to 600 ° C. The substrate 101 was held at the same temperature until a streak (light stripe) due to cubic 3C type silicon carbide appeared in the RHEED pattern, and the silicon carbide layer 102 was formed on the surface of the silicon single crystal substrate 101. Based on the lattice constant of the silicon single crystal obtained from the RHEED pattern of the (111) silicon single crystal at 600 ° C., the lattice constant of the formed silicon carbide was calculated to be 0.450 nm. The layer thickness of silicon carbide layer 102 was about 2 nm, and the surface was a (111) crystal plane.

On the non-stoichiometric silicon carbide layer 102, a wurtzite crystal type hexagonal aluminum nitride (AlN) layer 103 is formed on the silicon carbide layer 102 using nitrogen plasma as a nitrogen source, and the temperature of the substrate 101 is set to 720. Formed as ° C. The nitrogen plasma was generated using an electron cyclotron resonance (ECR) type apparatus that applies a high frequency of 13.56 MHz and a magnetic field to high purity nitrogen gas. While maintaining the MBE growth chamber at a high vacuum of about 1 × 10 ⁻⁶ Pa, atomic nitrogen (nitrogen radicals) in the nitrogen plasma is extracted using electric repulsion and sprayed on the surface of the silicon carbide layer 102. did. The AlN layer 103 formed as a group III nitride semiconductor bonding layer according to the present invention had a thickness of about 15 nm and the surface was a {0001} crystal plane.

A hexagonal first n-type gallium nitride (GaN) 104a was formed on the hexagonal AlN layer 103 at 720 ° C. by MBE. The layer thickness of the first n-type GaN layer 104a, which is a constituent layer of the superlattice structure layer 104, was 10 ML (about 2.6 nm). The first n-type GaN layer 104a includes a first n-type aluminum nitride / gallium mixed crystal (Al) having an aluminum (Al) composition ratio of 0.10, which is another constituent layer of the superlattice structure layer 104. _0.10 Ga _0.90 N) 104b was provided. Next, the second n-type GaN layer 104a was joined to the first n-type Al _0.10 Ga _0.90 N mixed crystal layer 104b. A second Al _0.10 Ga _0.90 N mixed crystal layer 104b was joined to the second n-type GaN layer 104a. On the second _Al 0.10 _{Ga 0.90} N mixed crystal layer 104b, further, a third n-type GaN layer 104a and the third n-type _Al 0.10 _{Ga 0.90} N mixed crystal layer 104b To complete the formation of the superlattice structure layer 104. The thicknesses of the first to third n-type Al _0.10 Ga _0.90 N mixed crystal layer 104b were all 10 ML.

  On the superlattice structure layer 104, a lower cladding layer 105 made of n-type GaN having a layer thickness of about 2200 nm was provided by doping silicon (Si) according to the MBE method. Since the n-type GaN layer 105 is provided via the superlattice structure layer 104, the surface roughness is r. m. s. It had a good flatness of about 1.0 nm in value.

On the lower clad layer 105, an n-type GaN barrier layer and an n-type gallium nitride / indium mixed crystal (Ga _0.85 In _0.15 N) are stacked alternately for five periods. A light emitting layer 106 having a multiple quantum well structure having the above-described structure was formed. An upper cladding layer 107 made of p-type Al _0.10 Ga _0.90 N (layer thickness: about 90 nm) was formed on the light emitting layer 106. Thus, a light emitting portion having a pn junction type double hetero (DH) junction structure was constituted by the n type clad layer 105, the n type light emitting layer 106, and the p type upper clad layer 107. A contact layer 108 made of p-type GaN (layer thickness: about 100 nm) was further provided on the p-type upper clad layer 107 forming the light-emitting portion to form the laminated structure 11 for LED 10 use.

  A p-type ohmic electrode 109 made of gold (element symbol: Au) and nickel (element symbol: Ni) oxide is formed on the surface of the p-type contact layer 108 which is the outermost layer of the multilayer structure 11. did. One n-type ohmic electrode 110 was formed after removing the light emitting layer 106, the upper cladding layer 107, and the contact layer 108 in the region where the electrode 110 was provided by a general dry etching means. Since the n-type ohmic electrode 110 was formed via the superlattice structure layer 104, it was provided on the surface of the lower cladding layer 105 that had good flatness. That is, in the LED 10, the p-type ohmic electrode 109 and the n-type ohmic electrode 110 are provided on the same surface side with respect to the silicon single crystal substrate 101.

The device operating current was passed between the p-type and n-type ohmic electrodes 109 and 110 of the LED chip 10 manufactured as described above, and the light emission and electrical characteristics were investigated. When a current was applied to the LED 10 in the forward direction, blue light having a dominant wavelength of 460 nm was emitted. When the forward current was 20 mA, the emission intensity was about 2.2 mW. The forward voltage (Vf) when a current of 20 mA was passed in the forward direction was about 3.4V. Further, since the silicon carbide layer 102 having a non-stoichiometric composition is provided as a buffer layer, a superlattice structure layer 104 made of a group III nitride semiconductor layer having excellent crystallinity thereon, and a DH structure type light emitting portion Was provided. For this reason, the reverse voltage when the reverse current was 10 μA was a high voltage of 15V. In particular, since the superlattice structure layer 104 and the light-emitting portion are made of a group III nitride semiconductor layer having excellent crystallinity, the reverse withstand voltage with almost no local breakdown voltage is obtained. An excellent LED could be constructed.
(Example 2)
In Example 1, a silicon carbide layer having a non-stoichiometric composition provided on a (001) silicon single crystal substrate having a (001) crystal plane as a surface, a cubic group III nitride semiconductor junction layer, a cubic crystal The present invention will be specifically described by taking as an example a case where a light emitting diode (LED) is manufactured from an epitaxial multilayer structure including a superlattice structure layer made of a group III nitride semiconductor layer.

  The cross-sectional structure of the semiconductor LED 20 produced in the present Example 2 is shown typically.

For the production of the LED 20, an n-type silicon single crystal having phosphorus (element symbol: P) with the (001) crystal plane as the surface was used as the substrate 201. After the substrate 201 was transferred into a growth chamber for MBE growth, the substrate 201 was heated to 800 ° C. in a high vacuum of about 5 × 10 ⁻⁷ Pascal (Pa). While monitoring the RHEED pattern, heating was continued at the same temperature until the (100) crystal plane forming the surface of the substrate 201 had a (2 × 1) rearrangement structure.

After confirming the appearance of the (2 × 2) rearrangement structure, the temperature was lowered to 420 ° C. while the substrate 201 was housed in the MBE growth chamber. Next, acetylene gas was sprayed onto the surface of the substrate 201, and acetylene was adsorbed on the surface while irradiating electrons. Electrons were generated by energizing and heating a tungsten (element symbol: W) filament disposed in a growth chamber maintained in a high vacuum. The electrons were irradiated at an acceleration voltage of 300 V and an area density of about 5 × 10 ¹² cm ⁻² . Acetylene gas and electrons were continuously supplied on the RHEED pattern until the electron diffraction spots due to the (2 × 1) rearrangement structure on the surface of the substrate 201 almost disappeared.

Thereafter, the silicon single crystal substrate 201 was heated to 550 ° C. When the temperature of the substrate 201 is stabilized at 550 ° C., the electrons are directed toward the substrate 201. I started to irradiate again. Until the streak due to cubic 3C type silicon carbide appears in the RHEED pattern, the surface of substrate 201 is continuously irradiated with electrons at the same temperature, and 3C type cubic silicon carbide layer 202 is formed on the surface of silicon single crystal substrate 201. Formed. At 600 ° C., the lattice constant of silicon carbide formed was calculated to be 0.440 nm based on the lattice constant of the silicon single crystal obtained from the RHEED pattern of the (001) silicon single crystal.
Further, in the RHEED pattern of the silicon carbide layer 202, abnormal diffraction due to twins and stacking faults was not observed. Moreover, the layer thickness of the silicon carbide layer 202 was about 2 nm, and the surface of the layer 202 was a (001) crystal plane.

A cubic zinc blende crystal type aluminum nitride (AlN) layer 203 is formed on the silicon carbide layer 202 having a non-stoichiometric composition by the MBE method using nitrogen plasma as a nitrogen source, and the temperature of the substrate 201 is increased. It was formed at 700 ° C. The nitrogen plasma was generated using an electron cyclotron resonance (ECR) type apparatus that applies a high frequency of 13.56 MHz and a magnetic field to high purity nitrogen gas. While maintaining the MBE growth chamber at a high vacuum of about 1 × 10 ⁻⁶ Pa, atomic nitrogen (nitrogen radicals) in the nitrogen plasma is extracted using electric repulsion and sprayed on the surface of the silicon carbide layer 202. did. The thickness of the AlN layer 203, which is a group III nitride semiconductor junction layer according to the present invention, was about 8 nm. The AlN layer 203 was a single crystal layer having a (001) crystal plane as a surface.

On the (001) crystal plane of the surface of the cubic AlN layer 203, cubic n-type gallium nitride (GaN) 204a was formed at 700 ° C. by the MBE method. The layer thickness of the first n-type GaN layer 204a, which is a constituent layer of the superlattice structure layer 204, was 15 ML (about 3.9 nm). The first n-type GaN layer 204a includes a first n-type gallium nitride / indium mixed crystal (Ga) having a gallium (Ga) composition ratio of 0.95, which is another constituent layer of the superlattice structure layer 204. _0.95 In _0.05 N) 204b was provided. Next, a second n-type GaN layer 204a was joined to the first n-type Ga _0.95 In _0.05 N mixed crystal layer 204b. A second Ga _0.95 In _0.05 N mixed crystal layer 204b was joined to the second n-type GaN layer 204a. On the second _Ga 0.95 _{In 0.05} N mixed crystal layer 204b, further, a third n-type GaN layer 204a and the third n-type _Ga 0.95 _{In 0.05} N mixed crystal layer 204b To complete the formation of the superlattice structure layer 204. The thicknesses of the first to third n-type Ga _0.95 In _0.05 N mixed crystal layer 204b were all 10 ML.

On the n-type Ga _0.95 In _0.05 N mixed crystal layer 204b whose surface is the (001) crystal plane that forms the outermost layer of the superlattice structure layer 204, silicon is doped by MBE method while doping silicon. A lower cladding layer 205 made of cubic and n-type GaN having a thickness of about 1800 nm was provided. Since the n-type GaN layer 205 is provided via the superlattice structure layer 204, the surface roughness is r. m. s. The film had a good flatness of about 1.2 nm.

On the lower clad layer 205, a multi-layered structure consisting of five pairs of a cubic n-type GaN barrier layer and a cubic n-type gallium nitride / indium mixed crystal (Ga _0.85 In _0.15 N) well layer. A light emitting layer 206 having a quantum well structure was formed at 700 ° C. by MBE. An upper cladding layer 207 made of cubic p-type Al _0.10 Ga _0.90 N and having a layer thickness of about 100 nm was formed on the light emitting layer 206. As a result, a light emitting portion having a pn junction type double hetero (DH) junction structure was constituted by the n type clad layer 205, the n type light emitting layer 206, and the p type upper clad layer 207. A contact layer 208 made of cubic p-type GaN having a layer thickness of about 90 nm is further provided on the p-type upper clad layer 207 forming the light emitting portion by the MBE method to form the laminated structure 21 for the LED 20 application. did.

  A p-type ohmic electrode 209 made of gold (Au) and nickel (Ni) oxide is formed at the center of the surface of the p-type contact layer 208 that forms the outermost layer of the multilayer structure 21. One n-type ohmic electrode 210 was configured by providing a gold vacuum deposition film on the entire back surface of the n-type silicon single crystal substrate 201.

The device operating current was passed between the p-type and n-type ohmic electrodes 209 and 210 of the LED chip 20 manufactured as described above, and the light emission and electrical characteristics were investigated. When a forward current was applied to the LED 20, blue light having a dominant wavelength of 465 nm was emitted. The light emission intensity when the forward current was 20 mA was as high as about 2.0 mW. The forward voltage (Vf) when a current of 20 mA was passed in the forward direction was about 3.3V. Further, since the silicon carbide layer 202 having a non-stoichiometric composition is provided as a buffer layer, a superlattice structure layer 204 made of a group III nitride semiconductor layer having excellent crystallinity thereon, and a DH structure type light emitting portion Was provided. For this reason, the reverse voltage when the reverse current was 10 μA was a high voltage of 15V. In particular, since the superlattice structure layer 204 and the light emitting portion are composed of a group III nitride semiconductor layer having excellent crystallinity, an LED having excellent reverse voltage resistance with little local breakdown voltage is configured. did it.
(Example 3)
The contents of the present invention will be specifically described by taking as an example a case where an LED having a group III nitride semiconductor junction layer made of aluminum nitride formed by nitriding a metal aluminum film is constructed.

  As described in Example 1 above, a cubic 3C type silicon carbide layer was formed on a (111) silicon single crystal substrate having a (111) crystal plane as a surface. Next, the surface of the silicon carbide layer having a lattice constant of 0.450 nm made of the (111) crystal plane was irradiated with an aluminum (Al) beam in an MBE growth chamber to form an Al film. . The film thickness of the Al coating was about 3 nm.

  Next, nitrogen plasma was generated in the chamber using an ECR (electron cyclotron resonance) type radio frequency (RF) plasma generator provided in the MBE growth chamber. Thereafter, nitrogen radicals in the nitrogen plasma were selectively extracted and irradiated on the Al film to nitride it. The AlN film formed by nitriding was assumed to be hexagonal from the RHEED pattern.

  A hexagonal AlN layer formed by nitriding an Al film is used as a group III nitride semiconductor junction layer, and a superlattice structure layer having the structure as described in Example 1 above, an n-type lower cladding layer thereon Then, an n-type light emitting layer, a p-type upper clad layer, and a p-type contact layer were sequentially laminated to form a laminated structure for LED use. By using the AlN layer formed by nitriding as the group III nitride semiconductor junction layer, any of the group III nitride semiconductor layers constituting the superlattice structure layer provided thereon is a hexagonal crystal system. It became a uniform standard. According to electron diffraction analysis and general cross-sectional TEM (transmission electron microscope) observation, the surface of each layer is a (0001) crystal plane, and the presence of cubic crystal lumps is almost absent in each layer. I was not able to admit.

  The stacked structure provided with a hexagonal AlN layer formed by nitriding as a group III nitride semiconductor junction layer is provided with p-type and n-type ohmic electrodes as described in Example 1 above, and an LED is formed. Configured.

  The emission wavelength when a forward current of 20 mA was passed through the LED was about 460 nm, which was substantially the same as the LED described in the above example. In addition, since an AlN layer in which the crystal system formed by nitriding the Al coating is uniformly unified to a hexagonal crystal is used as the group III nitride semiconductor junction layer, the hexagonal crystal is not mixed with a cubic crystal mass. Since the light emitting layer was formed from the group III nitride semiconductor crystal, the light emission wavelength between the LED chips was uniform.

  According to the present invention, a group III nitride semiconductor layer having excellent crystallinity and excellent surface flatness can be provided, and thus can be used as a high-performance semiconductor device.

10 LED
11 LED laminated structure 101 Silicon single crystal substrate 102 Non-stoichiometric silicon carbide layer 103 Group III nitride semiconductor junction layer (AlN layer)
104 Group III Nitride Semiconductor Superlattice Structure Layer 105 Group III Nitride Semiconductor Lower Cladding Layer 106 Group III Nitride Semiconductor Light-Emitting Layer 107 Group III Nitride Semiconductor Upper Cladding Layer 108 Group III Nitride Semiconductor Contact Layer 109 p-type Ohmic Electrode 110 n-type ohmic electrode 20 LED
21 LED multilayer structure 201 Silicon single crystal substrate 202 Non-stoichiometric silicon carbide layer 203 Group III nitride semiconductor junction layer (AlN layer)
204 Group III nitride semiconductor superlattice structure layer 205 Group III nitride semiconductor lower cladding layer 206 Group III nitride semiconductor light emitting layer 207 Group III nitride semiconductor upper cladding layer 208 Group III nitride semiconductor contact layer 209 p-type ohmic electrode 210 n-type ohmic electrode

Claims (8)

A silicon single crystal substrate, a silicon carbide layer provided on the surface of the substrate, a group III nitride semiconductor junction layer provided in contact with the silicon carbide layer, and a group III nitride on the group III nitride semiconductor junction layer A semiconductor device having a superlattice structure layer made of a semiconductor, wherein the silicon carbide layer is cubic and has a lattice constant of more than 0.436 nm and 0.460 nm or less, and is non-stoichiometrically rich in silicon. The group III nitride semiconductor junction layer has a composition of Al _X Ga _Y In _{ZN 1-α} M _α (0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1, 0 ≦ α < 1 and M are Group V elements other than nitrogen.) A semiconductor element. The superlattice structure layer made of a group III nitride semiconductor is a layer in which aluminum / gallium nitride (Al _X Ga _1-X N: 0 ≦ X ≦ 1) layers having different aluminum (Al) compositions are alternately stacked. The semiconductor element according to claim 1. 3. The semiconductor element according to claim 2, wherein the aluminum nitride / gallium layer having a different aluminum composition and having a small aluminum composition is in contact with the group III nitride semiconductor junction layer. The superlattice structure layer made of a group III nitride semiconductor is a layer in which gallium nitride indium (Ga _Q In _1-Q N: 0 ≦ Q ≦ 1) layers having different gallium (Ga) compositions are alternately stacked. The semiconductor element according to claim 1. 5. The semiconductor device according to claim 4, wherein a gallium nitride / indium layer having a different gallium composition and having a large gallium composition is in contact with a group III nitride semiconductor junction layer. 6. The semiconductor device according to claim 1, wherein the superlattice structure layer made of a group III nitride semiconductor has a thickness in a range of 5 monolayers (ML) to 30 ML. . The silicon single crystal substrate is a substrate having a {111} crystal surface, and the group III nitride semiconductor junction layer is a hexagonal wurtzite crystal type aluminum nitride (AlN) layer. Item 7. The semiconductor element according to any one of Items 1 to 6. The silicon single crystal substrate is a substrate having a {001} crystal surface, and the group III nitride semiconductor junction layer is a cubic zinc blende crystal type aluminum nitride (AlN) layer. The semiconductor element according to claim 1.

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