WO2009119159A1 - Substrate for optical device and method for manufacturing the substrate - Google Patents

Substrate for optical device and method for manufacturing the substrate Download PDF

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WO2009119159A1
WO2009119159A1 PCT/JP2009/051871 JP2009051871W WO2009119159A1 WO 2009119159 A1 WO2009119159 A1 WO 2009119159A1 JP 2009051871 W JP2009051871 W JP 2009051871W WO 2009119159 A1 WO2009119159 A1 WO 2009119159A1
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buffer layer
layer
substrate
substrate member
optical device
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PCT/JP2009/051871
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French (fr)
Japanese (ja)
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名西　▲やす▼之
荒木　努
高橋　功次
大平　重男
悟仁 鈴木
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日本軽金属株式会社
学校法人立命館
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/18—Epitaxial-layer growth characterised by the substrate
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials
    • C30B23/02—Epitaxial-layer growth
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
    • C30B29/403—AIII-nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/0242—Crystalline insulating materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02439—Materials
    • H01L21/02455—Group 13/15 materials
    • H01L21/02458—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02436—Intermediate layers between substrates and deposited layers
    • H01L21/02494—Structure
    • H01L21/02496—Layer structure
    • H01L21/02502—Layer structure consisting of two layers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02538—Group 13/15 materials
    • H01L21/0254—Nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/0262—Reduction or decomposition of gaseous compounds, e.g. CVD
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02658—Pretreatments
    • H01L21/02661—In-situ cleaning

Definitions

  • the present invention relates to an optical device substrate and a method for manufacturing the same, and more particularly, to an optical device substrate having a gallium oxide single crystal substrate member and having a gallium nitride layer grown at a predetermined growth temperature as a surface layer. About.
  • Gallium nitride (GaN) -based nitride semiconductor layers are applied as materials for optical devices, and blue LEDs, green LEDs, white LEDs, blue-violet LEDs, etc. are already on the market.
  • a substrate member for such an optical device sapphire and SiC are used. If the substrate member is conductive, electrodes can be drawn out from the back surface of the substrate member to form a vertical device structure, allowing a larger current to flow than the horizontal structure, which can improve luminous efficiency. It is. Further, if the substrate member is transparent with respect to the emission wavelength, light can be extracted from both surfaces of the substrate member, and the light extraction efficiency can be improved. For this reason, a conductive and transparent substrate member is desired. However, sapphire in practical use is transparent but not conductive. On the other hand, SiC is conductive but opaque.
  • gallium oxide (Ga 2 O 3 ) has been attracting attention as a substrate member for growing a GaN-based nitride semiconductor layer because it has the property of being conductive and transparent.
  • Ga 2 O 3 gallium oxide
  • the present inventors have proposed a method of forming a GaN layer on the surface of the Ga 2 O 3 substrate member by nitriding, and then lattice matching with the GaN layer to be grown thereafter (Patent Document 1 and Patent Document 1 below) 2).
  • Patent Document 1 and Patent Document 1 below JP 2007-137727 A JP 2007-137728 A
  • the present invention has been made to solve such a conventional problem, and has a gallium nitride layer having excellent surface flatness and crystal quality while using a gallium oxide substrate member. And an object of the present invention is to provide a manufacturing method thereof.
  • an optical device substrate includes a gallium oxide single crystal substrate member and has a gallium nitride layer grown at a predetermined growth temperature as a surface layer.
  • a second buffer layer made of hexagonal gallium nitride, and a hexagonal gallium nitride layer grown on the surface of the second buffer layer at the predetermined growth temperature is a gallium oxide single crystal substrate member and has a gallium nitride layer grown at a predetermined growth temperature as a surface layer.
  • a method for manufacturing an optical device substrate according to the present invention includes a gallium nitride single crystal substrate member and a method for manufacturing an optical device substrate having a gallium nitride layer grown at a predetermined growth temperature as a surface layer.
  • a first buffer layer made of hexagonal gallium nitride is formed on the surface of the gallium oxide single crystal substrate member by nitriding the gallium oxide single crystal substrate member, and a predetermined amount is formed on the surface of the first buffer layer.
  • FIG. 2 is a diagram showing RHEED patterns on the surface of a Ga 2 O 3 substrate member before and after nitriding in Example 1.
  • FIG. 6 is a diagram showing an RHEED pattern on the surface of a second buffer layer in Example 1.
  • FIG. 2 is a diagram showing an RHEED pattern and an SEM image on the surface of a GaN layer in Example 1.
  • FIG. 3 is a diagram showing a cross-sectional TEM image of the optical device substrate according to Example 1.
  • FIG. 3 is a diagram showing an X-ray rocking curve of a GaN layer in Example 1.
  • FIG. 6 is a diagram illustrating a manufacturing process of an optical device substrate according to Comparative Example 1.
  • FIG. 6 is a diagram showing an RHEED pattern and an SEM image on the surface of a GaN layer in Comparative Example 1.
  • FIG. 10 is a diagram showing a cross-sectional TEM image of an optical device substrate according to Comparative Example 2.
  • FIG. 1 shows a cross-sectional structure of an optical device substrate according to an embodiment of the present invention.
  • a first buffer layer 2 made of hexagonal gallium nitride (GaN) formed by nitriding is disposed on the surface portion of the gallium oxide (Ga 2 O 3 ) single crystal substrate member 1.
  • a second buffer layer 3 made of hexagonal GaN grown at a temperature lower than a predetermined growth temperature is disposed on the surface of the first buffer layer 2, and further, a predetermined buffer layer is formed on the surface of the second buffer layer 3.
  • a hexagonal GaN layer 4 grown at a temperature of 5 mm is disposed.
  • Si silicon
  • HF hydrogen
  • GaAs gallium arsenide
  • the Ga 2 O 3 substrate member 1 subjected to such pretreatment is set in a vacuum vessel, and thermal cleaning is performed.
  • Thermal cleaning is a method in which the Ga 2 O 3 substrate member 1 is heated and cleaned, and the temperature is 750 ° C. to 850 ° C., preferably 800 ° C., and the heating time is 10 minutes to 60 minutes.
  • the Ga 2 O 3 substrate member 1 is nitrided. Nitrogen plasma is used for the nitriding treatment, but radio frequency (RF) plasma is used as a plasma excitation method. In this case, an excited plasma is generated by applying a high-frequency magnetic field to molecular nitrogen (N 2 ).
  • RF radio frequency
  • the GaN layer is grown using the RF plasma excitation molecular beam epitaxy (MBE) method. In this case, continuous processing from nitriding to GaN layer growth can be performed in the same apparatus, and efficient processing becomes possible.
  • ECR electron cyclotron resonance
  • MBE RF plasma excitation molecular beam epitaxy
  • the nitriding treatment is performed with the Ga 2 O 3 substrate member 1 at a temperature of 300 to 400 ° C., a plasma power of 300 to 350 W, a nitrogen flow rate of 2 to 3 sccm, and a nitriding time of 60 to 100 minutes. If the nitridation time is shorter than 60 minutes, the formation of the nitride layer becomes insufficient, and cubic GaN is preferentially formed, and the formation of hexagonal GaN requires more than 60 minutes. Conversely, even if the nitriding time exceeds 100 minutes, the thickness of the nitrided layer becomes saturated and constant. For this reason, a nitriding time of 60 to 100 minutes is preferable. By such nitriding treatment, the first buffer layer 2 made of hexagonal GaN is formed.
  • the second buffer layer 3 made of hexagonal GaN is grown on the surface of the nitrided Ga 2 O 3 substrate member 1.
  • the temperature of the Ga 2 O 3 substrate member 1 is 480 to 520 ° C.
  • the plasma power is 250 to 350 W
  • the nitrogen flow rate is 1.5 to 2.5 sccm
  • the growth time is 5 to 15 minutes. If the growth time is less than 5 minutes, the growth of the GaN layer will be insufficient.On the other hand, if the layer thickness increases beyond 15 minutes, defects and dislocations will be induced by stress generation, which will affect the subsequent growth of the GaN layer. Therefore, it is preferable that the growth time is within this range.
  • a hexagonal GaN layer 4 is grown on the surface of the second buffer layer 3.
  • the GaN layer 4 is grown at a temperature of 650 to 750 ° C., a plasma power of 250 to 350 W, a nitrogen flow rate of 1.5 to 2.5 sccm, and a growth time of 50 to 90 minutes of the Ga 2 O 3 substrate member 1.
  • the second buffer layer 3 made of hexagonal GaN is further grown and formed.
  • various optical devices such as a light emitting element and a light receiving element, can be manufactured by using the board
  • this optical device substrate can be used as a template substrate, and a hexagonal GaN layer can be produced with good reproducibility on the GaN layer serving as the surface layer.
  • Example 1 First, a Ga 2 O 3 single crystal was grown by the floating zone (FZ) method. At this time, Ga 2 O 3 powder (purity 4N) was molded with a rubber tube and then sintered, and a single crystal was grown using this as a raw material rod. The single crystal growth conditions are a growth rate of 7.5 mm / h in a dry air atmosphere. The grown single crystal was cut into a thickness of 8 mm ⁇ 8 mm ⁇ 0.8 mm, and polished so that the (100) face became the surface, to a thickness of 0.4 mm.
  • FZ floating zone
  • This substrate member was introduced into an RF-MBE apparatus, heated to a temperature near 800 ° C., and then thermally cleaned by holding for 10 minutes. Thereafter, nitriding treatment was performed with nitrogen plasma excited by RF.
  • the nitriding conditions are a substrate member temperature of 300 ° C., an RF plasma power of 350 W, a nitrogen flow rate of 2.5 sccm, and a nitriding time of 90 minutes.
  • FIG. 3 shows the results of observation of reflection high-energy electron diffraction (RHEED) patterns on the surface of the Ga 2 O 3 substrate member before and after nitriding.
  • RHEED reflection high-energy electron diffraction
  • FIG. 4 shows an RHEED pattern when an electron beam is incident on the surface of the second buffer layer from the [11-20] direction or the [1-100] direction. A sharp streak pattern was observed similar to the surface of the Ga 2 O 3 substrate member after nitriding shown in FIG.
  • FIG. 5 shows a RHEED pattern and a surface SEM photograph of the GaN layer when an electron beam is incident on the surface of the formed GaN layer from the [11-20] orientation. RHEED is a streak-like pattern, and SEM photographs confirm that the surface has excellent flatness.
  • FIG. 6 shows a TEM cross section from the surface of the Ga 2 O 3 substrate member to the GaN layer in the optical device substrate thus manufactured. Further, when the crystallinity of the GaN layer produced in Example 1 was evaluated by an X-ray rocking curve, as shown in FIG. 7, the FWHM of GaN (002) was 22.0 arcmin with a single peak. It was.
  • Example 2 An optical device substrate was manufactured under the same conditions as in Example 1 above, except that the substrate member temperature when forming the GaN layer on the surface of the second buffer layer was set to 700 ° C. When the crystallinity of the produced GaN layer was evaluated by an X-ray rocking curve, the FWHM of the GaN (002) peak was 22.1 arcmin.
  • FIG. 8 shows a GaN layer was grown directly at a high temperature on the nitrided Ga 2 O 3 substrate member surface without forming a second buffer layer.
  • the growth temperature is set to 780 ° C. and 700 ° C. in the RF-MBE apparatus, and the growth time is 60 minutes. GaN growth for layer formation was performed.
  • FIG. 9 shows an RHEED pattern and a surface SEM photograph of the GaN layer when an electron beam is incident on the surface of the formed GaN layer from the [11-20] direction.
  • the growth temperature was 780 ° C., it was confirmed that peeling occurred in the GaN layer.
  • the GaN layer grown at a growth temperature of 700 ° C was able to suppress delamination, but the RHEED pattern was not a streak but a spot, and the surface flatness was found to be low from SEM photographs. did.
  • the FWHM of the GaN (002) peak measured by the X-ray rocking curve is 41.8 arcmin when the growth temperature is 780 ° C, and 83.0arcmin when the growth temperature is 700 ° C.
  • the GaN (002) peak in the GaN layers obtained in Examples 1 and 2 was 2 to 4 times larger than the FWHM. From this, it was found that the formation of the second buffer layer in the present invention is effective not only for the flatness of the GaN layer but also for improving the crystallinity.
  • FIG. 10 shows a cross-sectional TEM image of an optical device substrate described in the document EGVillora et al., Appl. Phys. Lett., 90 (2007) 234102.
  • a GaN layer having a thickness of about 400 nm is formed on the nitride layer on the surface of the Ga 2 O 3 substrate member indicated by a without forming the second buffer layer.
  • the GaN layer without the stacking fault itself is formed on the second buffer layer having a thickness of about 100 nm. That is, when the second buffer layer is not formed, GaN growth with a thickness of about 200 nm is necessary to eliminate stacking faults, whereas the thickness is formed on the nitride layer on the surface of the Ga 2 O 3 substrate member.
  • the second buffer layer By forming the second buffer layer by GaN growth of about 100 nm, a GaN layer free from stacking faults can be obtained. Therefore, it can be seen that the formation of the second buffer layer is effective from the viewpoint of production efficiency, manufacturing cost, and the like.
  • the second buffer layer made of gallium nitride is grown at a temperature lower than a predetermined growth temperature, and Since the gallium nitride layer is grown on the surface of the second buffer layer at a predetermined growth temperature, the light having a gallium nitride layer having excellent surface flatness and excellent crystal quality while using a gallium oxide substrate member A device substrate can be obtained.

Abstract

Provided is a substrate for an optical device having a gallium nitride layer, which has excellent surface planarity even a gallium oxide substrate member is used, and excellent crystal qualities. A method for manufacturing such substrate for the optical device is also provided. The Ga2O3 substrate member to which thermal cleaning is performed is nitrided, a first buffer layer composed of hexagonal GaN is formed on a surface of the Ga2O3 substrate member, and a second buffer layer composed of hexagonal GaN is grown on the surface of the first buffer layer at a growing temperature of 480-520°C. Then, on the surface of the second buffer layer, a hexagonal GaN layer is grown as a surface layer of the optical device substrate at a growing temperature of 650-750°C.

Description

光デバイス用基板及びその製造方法Optical device substrate and manufacturing method thereof
　本発明は、光デバイス用基板及びその製造方法に係り、特に酸化ガリウム単結晶基板部材を備えると共に表面層として所定の成長温度で成長形成された窒化ガリウム層を有する光デバイス用基板及びその製造方法に関する。 The present invention relates to an optical device substrate and a method for manufacturing the same, and more particularly, to an optical device substrate having a gallium oxide single crystal substrate member and having a gallium nitride layer grown at a predetermined growth temperature as a surface layer. About.
　窒化ガリウム（GaN）系窒化物半導体層は、光デバイス用材料として応用され、すでに青色LED、緑色LED、白色LED、青紫LEDなどが市販されている。このような光デバイス用の基板部材として、サファイア及びSiCが用いられている。基板部材が導電性であれば、基板部材の背面から電極を引き出して縦型のデバイス構造を形成することができるので、横型構造よりも大きな電流を流すことが可能となり、発光効率の向上が見込まれる。また、基板部材が発光波長に対して透明であれば、基板部材の両面から光を取り出すことができ、光の取り出し効率の向上を図ることができる。このため、導電性があり且つ透明な基板部材が望まれている。しかしながら、実用化されているサファイアは透明であるが導電性がない。一方、SiCは導電性があるが不透明である。 Gallium nitride (GaN) -based nitride semiconductor layers are applied as materials for optical devices, and blue LEDs, green LEDs, white LEDs, blue-violet LEDs, etc. are already on the market. As a substrate member for such an optical device, sapphire and SiC are used. If the substrate member is conductive, electrodes can be drawn out from the back surface of the substrate member to form a vertical device structure, allowing a larger current to flow than the horizontal structure, which can improve luminous efficiency. It is. Further, if the substrate member is transparent with respect to the emission wavelength, light can be extracted from both surfaces of the substrate member, and the light extraction efficiency can be improved. For this reason, a conductive and transparent substrate member is desired. However, sapphire in practical use is transparent but not conductive. On the other hand, SiC is conductive but opaque.
　これに対し、酸化ガリウム（Ga2O3）は、導電性があり且つ透明である、という特性を有するため、GaN系窒化物半導体層の成長用基板部材として注目されている。
　ところが、Ga2O3とGaNとの格子定数のミスマッチが大きいため、Ga2O3基板部材上にGaNを成長させようとするとき、欠陥や転位が入ってしまい、高品質のGaN層を成長させることができないという問題があった。そこで、本発明者等は、Ga2O3基板部材を窒化処理することでその表面にGaN層を形成し、その後に成長させるGaN層との格子整合させる方法を提案した（下記特許文献１及び２参照）。
特開２００７－１３７７２７号公報 特開２００７－１３７７２８号公報 On the other hand, gallium oxide (Ga 2 O 3 ) has been attracting attention as a substrate member for growing a GaN-based nitride semiconductor layer because it has the property of being conductive and transparent.
However, due to the large lattice constant mismatch between Ga 2 O 3 and GaN, when trying to grow GaN on a Ga 2 O 3 substrate member, defects and dislocations enter and grow a high-quality GaN layer. There was a problem that it could not be made. Therefore, the present inventors have proposed a method of forming a GaN layer on the surface of the Ga 2 O 3 substrate member by nitriding, and then lattice matching with the GaN layer to be grown thereafter (Patent Document 1 and Patent Document 1 below) 2).
JP 2007-137727 A JP 2007-137728 A
　しかしながら、窒化処理したGa2O3基板部材上にGaN層を成長させても、必ずしも平坦で高品質な層であるとは言い難く、発光効率を向上させるためには、さらなる高品質なGaN層成長方法が必要となった。また、従来の方法では、Ga2O3基板部材の窒化処理にはプラズマ密度の高い電子サイクロトロン共鳴（ECR）プラズマを用い、分子線エピタキシー（MBE）法によるGaN層成長には高周波（RF）プラズマを用いていたため、窒化処理とGaN層成長とで使用する装置が異なっていた。このため、これらの工程を連続処理することができず、窒化処理後の半製品を一旦大気中に出して、次工程であるGaN層成長用の装置へ移動させる必要があった。 However, even if a GaN layer is grown on a nitrided Ga 2 O 3 substrate member, it is not always a flat and high-quality layer, and in order to improve luminous efficiency, an even higher-quality GaN layer is required. A growth method was needed. In addition, in the conventional method, electron cyclotron resonance (ECR) plasma with high plasma density is used for nitriding treatment of Ga 2 O 3 substrate members, and radio frequency (RF) plasma is used for GaN layer growth by molecular beam epitaxy (MBE) method. Therefore, the devices used for nitriding and GaN layer growth were different. For this reason, these processes cannot be performed continuously, and the semi-finished product after the nitriding process has to be once taken out into the atmosphere and moved to the apparatus for growing the GaN layer as the next process.
　本発明は、このような従来の問題点を解消するためになされたもので、酸化ガリウム基板部材を用いながらも表面平坦性に優れ且つ結晶品質性に優れた窒化ガリウム層を有する光デバイス用基板及びその製造方法を提供することを目的としている。 The present invention has been made to solve such a conventional problem, and has a gallium nitride layer having excellent surface flatness and crystal quality while using a gallium oxide substrate member. And an object of the present invention is to provide a manufacturing method thereof.
　上述した課題を解決するため、本発明に係る光デバイス用基板は、酸化ガリウム単結晶基板部材を備えると共に表面層として所定の成長温度で成長形成された窒化ガリウム層を有する光デバイス用基板において、前記酸化ガリウム単結晶基板部材の表面上に窒化処理により形成された六方晶窒化ガリウムからなる第１のバッファ層と、前記第１のバッファ層の表面上に所定の成長温度より低い温度で成長形成された六方晶窒化ガリウムからなる第２のバッファ層と、前記第２のバッファ層の表面上に前記所定の成長温度で成長形成された六方晶窒化ガリウム層とを備えたことを特徴とする。 In order to solve the above-described problems, an optical device substrate according to the present invention includes a gallium oxide single crystal substrate member and has a gallium nitride layer grown at a predetermined growth temperature as a surface layer. A first buffer layer made of hexagonal gallium nitride formed by nitriding on the surface of the gallium oxide single crystal substrate member, and grown on the surface of the first buffer layer at a temperature lower than a predetermined growth temperature And a second buffer layer made of hexagonal gallium nitride, and a hexagonal gallium nitride layer grown on the surface of the second buffer layer at the predetermined growth temperature.
　また、本発明に係る光デバイス用基板の製造方法は、酸化ガリウム単結晶基板部材を備えると共に表面層として所定の成長温度で成長形成された窒化ガリウム層を有する光デバイス用基板の製造方法において、前記酸化ガリウム単結晶基板部材を窒化処理することにより前記酸化ガリウム単結晶基板部材の表面上に六方晶窒化ガリウムからなる第１のバッファ層を形成し、前記第１のバッファ層の表面上に所定の成長温度より低い温度で六方晶窒化ガリウムからなる第２のバッファ層を成長形成し、前記第２のバッファ層の表面上に前記所定の成長温度で六方晶窒化ガリウム層を成長形成することを特徴とする。 In addition, a method for manufacturing an optical device substrate according to the present invention includes a gallium nitride single crystal substrate member and a method for manufacturing an optical device substrate having a gallium nitride layer grown at a predetermined growth temperature as a surface layer. A first buffer layer made of hexagonal gallium nitride is formed on the surface of the gallium oxide single crystal substrate member by nitriding the gallium oxide single crystal substrate member, and a predetermined amount is formed on the surface of the first buffer layer. Growing a second buffer layer made of hexagonal gallium nitride at a temperature lower than the growth temperature of the first, and growing a hexagonal gallium nitride layer at the predetermined growth temperature on the surface of the second buffer layer. Features.
本発明の実施の形態に係る光デバイス用基板の構造を示す断面図である。It is sectional drawing which shows the structure of the board | substrate for optical devices which concerns on embodiment of this invention. 実施の形態に係る光デバイス用基板の製造工程を示す図である。It is a figure which shows the manufacturing process of the board | substrate for optical devices which concerns on embodiment. 実施例１における窒化前後のGa2O3基板部材表面のRHEEDパターンを示す図である。 2 is a diagram showing RHEED patterns on the surface of a Ga 2 O 3 substrate member before and after nitriding in Example 1. FIG. 実施例１における第２のバッファ層表面のRHEEDパターンを示す図である。6 is a diagram showing an RHEED pattern on the surface of a second buffer layer in Example 1. FIG. 実施例１におけるGaN層表面のRHEEDパターンとSEM像を示す図である。2 is a diagram showing an RHEED pattern and an SEM image on the surface of a GaN layer in Example 1. FIG. 実施例１に係る光デバイス用基板の断面TEM像を示す図である。3 is a diagram showing a cross-sectional TEM image of the optical device substrate according to Example 1. FIG. 実施例１におけるGaN層のX線ロッキングカーブを示す図である。3 is a diagram showing an X-ray rocking curve of a GaN layer in Example 1. FIG. 比較例１に係る光デバイス用基板の製造工程を示す図である。6 is a diagram illustrating a manufacturing process of an optical device substrate according to Comparative Example 1. FIG. 比較例１におけるGaN層表面のRHEEDパターンとSEM像を示す図である。6 is a diagram showing an RHEED pattern and an SEM image on the surface of a GaN layer in Comparative Example 1. FIG. 比較例２に係る光デバイス用基板の断面TEM像を示す図である。10 is a diagram showing a cross-sectional TEM image of an optical device substrate according to Comparative Example 2. FIG.
　以下、本発明の実施の形態を添付図面に基づいて説明する。
　図１に本発明の実施の形態に係る光デバイス用基板の断面構造を示す。酸化ガリウム（Ga2O3）単結晶基板部材１の表面部分に窒化処理により形成された六方晶窒化ガリウム（GaN）からなる第１のバッファ層２が配置されている。この第１のバッファ層２の表面上に所定の成長温度より低い温度で成長形成された六方晶GaNからなる第２のバッファ層３が配置され、さらに第２のバッファ層３の表面上に所定の温度で成長形成された六方晶GaN層４が配置されている。 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a cross-sectional structure of an optical device substrate according to an embodiment of the present invention. A first buffer layer 2 made of hexagonal gallium nitride (GaN) formed by nitriding is disposed on the surface portion of the gallium oxide (Ga 2 O 3 ) single crystal substrate member 1. A second buffer layer 3 made of hexagonal GaN grown at a temperature lower than a predetermined growth temperature is disposed on the surface of the first buffer layer 2, and further, a predetermined buffer layer is formed on the surface of the second buffer layer 3. A hexagonal GaN layer 4 grown at a temperature of 5 mm is disposed.
　この光デバイス用基板は、図２に示すような工程により製造することができる。
　まず、Ga2O3基板部材１に対して、アセトン、メタノールによる有機洗浄をそれぞれ10分行った後、窒化前の前処理として、シリコン（Si）の酸化物処理に通常使用しているフッ化水素（HF）により10分のHF処理を行い、さらに、ガリウム砒素（GaAs）基板の洗浄に通常用いている溶液（H2O：H2SO4：H2O2＝1：4：1）により60℃、5分のエッチャント処理を行う。 This optical device substrate can be manufactured by a process as shown in FIG.
First, the Ga 2 O 3 substrate member 1 is subjected to organic cleaning with acetone and methanol for 10 minutes, respectively. Then, as a pretreatment before nitriding, the fluoride used normally for silicon (Si) oxide treatment HF treatment for 10 minutes with hydrogen (HF), and a solution usually used for cleaning gallium arsenide (GaAs) substrates (H 2 O: H 2 SO 4 : H 2 O 2 = 1: 4: 1) Perform an etchant treatment at 60 ° C for 5 minutes.
　このような前処理が施されたGa2O3基板部材１を真空容器内にセットし、サーマルクリーニングを行う。サーマルクリーニングはGa2O3基板部材１を加熱してクリーニングする方法で、温度750℃～850℃、好ましくは800℃、加熱時間10分～60分とする。
　次に、Ga2O3基板部材１を窒化処理する。窒化処理は、窒素プラズマを用いるが、プラズマ励起の方法として高周波（RF）プラズマを用いる。この場合、分子状窒素（N2）に高周波の磁界をかけて、励起したプラズマを発生させる。RFプラズマよりプラズマ密度が高い電子サイクロトロン共鳴（ECR）プラズマを用いることもできるが、GaN層の成長にはRFプラズマ励起による分子線エピタキシー（MBE）法を用いるため、窒化処理にRFプラズマを使用すれば、同一装置内で窒化からGaN層成長まで連続的に処理できることとなり、効率的な処理が可能となる。 The Ga 2 O 3 substrate member 1 subjected to such pretreatment is set in a vacuum vessel, and thermal cleaning is performed. Thermal cleaning is a method in which the Ga 2 O 3 substrate member 1 is heated and cleaned, and the temperature is 750 ° C. to 850 ° C., preferably 800 ° C., and the heating time is 10 minutes to 60 minutes.
Next, the Ga 2 O 3 substrate member 1 is nitrided. Nitrogen plasma is used for the nitriding treatment, but radio frequency (RF) plasma is used as a plasma excitation method. In this case, an excited plasma is generated by applying a high-frequency magnetic field to molecular nitrogen (N 2 ). Although electron cyclotron resonance (ECR) plasma, which has a higher plasma density than RF plasma, can be used, the GaN layer is grown using the RF plasma excitation molecular beam epitaxy (MBE) method. In this case, continuous processing from nitriding to GaN layer growth can be performed in the same apparatus, and efficient processing becomes possible.
　窒化処理は、Ga2O3基板部材１の温度300～400℃、プラズマパワー300～350W、窒素流量2～3sccm、窒化時間60～100分として行う。窒化時間が60分より短いと、窒化層の形成が不十分となり、立方晶GaNが優先的に形成されてしまい、六方晶GaN形成には60分を超える窒化時間が必要である。逆に、窒化時間が100分を超えても、窒化層の厚さは飽和して一定になる。このため、窒化時間60～100分が好ましい。このような窒化処理により、六方晶GaNからなる第１のバッファ層２が形成される。 The nitriding treatment is performed with the Ga 2 O 3 substrate member 1 at a temperature of 300 to 400 ° C., a plasma power of 300 to 350 W, a nitrogen flow rate of 2 to 3 sccm, and a nitriding time of 60 to 100 minutes. If the nitridation time is shorter than 60 minutes, the formation of the nitride layer becomes insufficient, and cubic GaN is preferentially formed, and the formation of hexagonal GaN requires more than 60 minutes. Conversely, even if the nitriding time exceeds 100 minutes, the thickness of the nitrided layer becomes saturated and constant. For this reason, a nitriding time of 60 to 100 minutes is preferable. By such nitriding treatment, the first buffer layer 2 made of hexagonal GaN is formed.
　次に、窒化処理したGa2O3基板部材１の表面上に六方晶GaNからなる第２のバッファ層３を成長形成させる。このとき、Ga2O3基板部材１の温度480～520℃、プラズマパワー250～350W、窒素流量1.5～2.5sccm、成長時間5～15分とする。成長時間が5分に満たないと、GaN層の成長が不十分となり、逆に15分を越えて層厚が厚くなると、応力発生により欠陥や転位が誘発され、その後のGaN層成長に影響を及ぼすため、この範囲内の成長時間で成長させることが好ましい。 Next, the second buffer layer 3 made of hexagonal GaN is grown on the surface of the nitrided Ga 2 O 3 substrate member 1. At this time, the temperature of the Ga 2 O 3 substrate member 1 is 480 to 520 ° C., the plasma power is 250 to 350 W, the nitrogen flow rate is 1.5 to 2.5 sccm, and the growth time is 5 to 15 minutes. If the growth time is less than 5 minutes, the growth of the GaN layer will be insufficient.On the other hand, if the layer thickness increases beyond 15 minutes, defects and dislocations will be induced by stress generation, which will affect the subsequent growth of the GaN layer. Therefore, it is preferable that the growth time is within this range.
　続いて、第２のバッファ層３の表面上に六方晶GaN層４を成長形成させる。このGaN層４の成長は、Ga2O3基板部材１の温度650～750℃、プラズマパワー250～350W、窒素流量1.5～2.5sccm、成長時間50～90分で行う。
　このようにして、Ga2O3基板部材１上に窒化処理により六方晶GaNからなる第１のバッファ層２を形成した後、さらに六方晶GaNからなる第２のバッファ層３を成長形成し、この第２のバッファ層３を介してGaN層４を成長させることで、表面平坦性及び結晶品質性に優れた六方晶GaN層４を得ることができる。 Subsequently, a hexagonal GaN layer 4 is grown on the surface of the second buffer layer 3. The GaN layer 4 is grown at a temperature of 650 to 750 ° C., a plasma power of 250 to 350 W, a nitrogen flow rate of 1.5 to 2.5 sccm, and a growth time of 50 to 90 minutes of the Ga 2 O 3 substrate member 1.
In this way, after the first buffer layer 2 made of hexagonal GaN is formed on the Ga 2 O 3 substrate member 1 by nitriding, the second buffer layer 3 made of hexagonal GaN is further grown and formed. By growing the GaN layer 4 through the second buffer layer 3, the hexagonal GaN layer 4 having excellent surface flatness and crystal quality can be obtained.
　なお、本発明に係る光デバイス用基板を用いることにより、発光素子、受光素子等の各種の光デバイスを製造することができる。
　また、この光デバイス用基板をテンプレート基板として使用し、表面層となるGaN層の上に六方晶GaN層を再現性よく作製することもできる。 In addition, various optical devices, such as a light emitting element and a light receiving element, can be manufactured by using the board | substrate for optical devices which concerns on this invention.
Further, this optical device substrate can be used as a template substrate, and a hexagonal GaN layer can be produced with good reproducibility on the GaN layer serving as the surface layer.
（実施例１）
　まず、Ga2O3単結晶をフローティングゾーン（FZ）法で育成した。このとき、Ga2O3粉末（純度4N）をラバーチューブで成形後、焼結し、これを原料棒として単結晶育成を行った。単結晶育成条件は、ドライエア雰囲気中で、成長速度7.5ｍｍ/ｈである。
　育成した単結晶を8mm×8mm×0.8mm厚に切り出し、（100）面が表面になるように研磨加工し、0.4mm厚とした。さらに、基板部材洗浄としてアセトン、メタノールによる有機洗浄をそれぞれ10分行った後、窒化前の基板部材の前処理として、HF処理10分、溶液（H2O：H2SO4：H2O2＝1：4：1）によるエッチャント処理5分を行った。 Example 1
First, a Ga 2 O 3 single crystal was grown by the floating zone (FZ) method. At this time, Ga 2 O 3 powder (purity 4N) was molded with a rubber tube and then sintered, and a single crystal was grown using this as a raw material rod. The single crystal growth conditions are a growth rate of 7.5 mm / h in a dry air atmosphere.
The grown single crystal was cut into a thickness of 8 mm × 8 mm × 0.8 mm, and polished so that the (100) face became the surface, to a thickness of 0.4 mm. Furthermore, organic cleaning with acetone and methanol was performed for 10 minutes each for substrate member cleaning, and then HF treatment was performed for 10 minutes as a pretreatment for the substrate member before nitriding, and the solution (H 2 O: H 2 SO 4 : H 2 O 2 = 1: 4: 1) Etchant treatment for 5 minutes.
　この基板部材をRF-MBE装置に導入し、温度800℃付近まで加熱した後、10分間保持することによるサーマルクリーニングを行った。その後、RF励起した窒素プラズマによる窒化処理を行った。窒化条件は、基板部材温度300℃、RFプラズマパワー350W、窒素流量2.5sccm、窒化時間90分である。 This substrate member was introduced into an RF-MBE apparatus, heated to a temperature near 800 ° C., and then thermally cleaned by holding for 10 minutes. Thereafter, nitriding treatment was performed with nitrogen plasma excited by RF. The nitriding conditions are a substrate member temperature of 300 ° C., an RF plasma power of 350 W, a nitrogen flow rate of 2.5 sccm, and a nitriding time of 90 minutes.
　図３に、窒化前後のGa2O3基板部材表面の反射高速電子回折（RHEED）パターンを観察した結果を示す。窒化前のGa2O3基板部材表面に対しては電子線を[010]方位から入射させたときのパターン、窒化後のGa2O3基板部材表面に対しては電子線を[11-20]方位または[1-100]方位から入射させたときのパターンが示されている。Ga2O3基板部材を窒化することで、シャープなストリークパターンが得られた様子を確認することができる。この窒化後のパターンは解析の結果、六方晶GaNであることがわかった。 FIG. 3 shows the results of observation of reflection high-energy electron diffraction (RHEED) patterns on the surface of the Ga 2 O 3 substrate member before and after nitriding. For Ga 2 O 3 substrate member surface before nitriding pattern when irradiation of an electron beam incident from [010] orientation, the electron beam with respect to Ga 2 O 3 substrate member surface after nitriding [11-20 The pattern when the light is incident from the [1] or [1-100] direction is shown. It can be confirmed that a sharp streak pattern is obtained by nitriding the Ga 2 O 3 substrate member. As a result of analysis, the pattern after nitriding was found to be hexagonal GaN.
　次に、同じRF-MBE装置内で第２のバッファ層形成のためのGaN成長を行った。成長条件は、基板部材温度500℃、RFパワー300W、窒素流量2.0sccm、Gaセル温度940℃、成長時間10分である。この第２のバッファ層表面に対して電子線を[11-20]方位または[1-100]方位から入射させたときのRHEEDパターンを図４に示す。図３に示した窒化後のGa2O3基板部材表面と同様にシャープなストリークパターンが観察された。 Next, GaN growth for forming the second buffer layer was performed in the same RF-MBE apparatus. The growth conditions are a substrate member temperature of 500 ° C., an RF power of 300 W, a nitrogen flow rate of 2.0 sccm, a Ga cell temperature of 940 ° C., and a growth time of 10 minutes. FIG. 4 shows an RHEED pattern when an electron beam is incident on the surface of the second buffer layer from the [11-20] direction or the [1-100] direction. A sharp streak pattern was observed similar to the surface of the Ga 2 O 3 substrate member after nitriding shown in FIG.
　さらに、第２のバッファ層の表面上にGaN層形成のためのGaN成長を行った。成長条件は、第２のバッファ層形成のための成長条件とは基板部材温度と成長時間が異なり、基板部材温度650℃、RFパワー300W、窒素流量2.0sccm、Gaセル温度940℃、成長時間60分である。図５は、形成されたGaN層表面に対して電子線を[11-20]方位から入射させたときのRHEEDパターンとGaN層の表面SEM写真を示す。RHEEDはストリーク状のパターンで、SEM写真から表面は優れた平坦性を有することが確認される。 Furthermore, GaN growth for forming a GaN layer was performed on the surface of the second buffer layer. The growth conditions are different from the growth conditions for forming the second buffer layer. The substrate member temperature and the growth time are different. The substrate member temperature is 650 ° C., the RF power is 300 W, the nitrogen flow rate is 2.0 sccm, the Ga cell temperature is 940 ° C., and the growth time is 60 Minutes. FIG. 5 shows a RHEED pattern and a surface SEM photograph of the GaN layer when an electron beam is incident on the surface of the formed GaN layer from the [11-20] orientation. RHEED is a streak-like pattern, and SEM photographs confirm that the surface has excellent flatness.
　このようにして製造された光デバイス用基板におけるGa2O3基板部材表面からGaN層にかけてのTEM断面を図６に示す。
　また、この実施例１で作製したGaN層の結晶性をX線ロッキングカーブで評価したところ、図７に示すように、シングルピークで、GaN(002)の半値幅（FWHM）は22.0 arcminであった。 FIG. 6 shows a TEM cross section from the surface of the Ga 2 O 3 substrate member to the GaN layer in the optical device substrate thus manufactured.
Further, when the crystallinity of the GaN layer produced in Example 1 was evaluated by an X-ray rocking curve, as shown in FIG. 7, the FWHM of GaN (002) was 22.0 arcmin with a single peak. It was.
（実施例２）
　第２のバッファ層の表面上にGaN層を形成する際の基板部材温度を700℃とした他は、上記の実施例１と同様の条件で光デバイス用基板を製造した。
　作製したGaN層の結晶性をX線ロッキングカーブで評価したところ、GaN(002)ピークのFWHMは22.1 arcminであった。 (Example 2)
An optical device substrate was manufactured under the same conditions as in Example 1 above, except that the substrate member temperature when forming the GaN layer on the surface of the second buffer layer was set to 700 ° C.
When the crystallinity of the produced GaN layer was evaluated by an X-ray rocking curve, the FWHM of the GaN (002) peak was 22.1 arcmin.
（比較例１）
　図８に示されるように、第２のバッファ層を形成することなく、窒化したGa2O3基板部材表面上に直接GaN層を高温で成長させた。Ga2O3基板部材のサーマルクリーニング及び窒化処理を上記の実施例と同じ条件で行った後、RF-MBE装置内で成長温度を780℃と700℃の２通りでそれぞれ成長時間60分としてGaN層形成のためのGaN成長を行った。
　形成されたGaN層表面に対して電子線を[11-20]方位から入射させたときのRHEEDパターンとGaN層の表面SEM写真を図９に示す。成長温度が780℃の場合は、GaN層に剥離が発生していることが確認された。一方、成長温度700℃で成長させたGaN層は、剥離を抑えることができたが、RHEEDパターンはストリーク状とはならずにスポット状となり、また、SEM写真から表面平坦性が低いことが判明した。 (Comparative Example 1)
As shown in FIG. 8, a GaN layer was grown directly at a high temperature on the nitrided Ga 2 O 3 substrate member surface without forming a second buffer layer. After performing thermal cleaning and nitridation treatment of the Ga 2 O 3 substrate member under the same conditions as in the above example, the growth temperature is set to 780 ° C. and 700 ° C. in the RF-MBE apparatus, and the growth time is 60 minutes. GaN growth for layer formation was performed.
FIG. 9 shows an RHEED pattern and a surface SEM photograph of the GaN layer when an electron beam is incident on the surface of the formed GaN layer from the [11-20] direction. When the growth temperature was 780 ° C., it was confirmed that peeling occurred in the GaN layer. On the other hand, the GaN layer grown at a growth temperature of 700 ° C was able to suppress delamination, but the RHEED pattern was not a streak but a spot, and the surface flatness was found to be low from SEM photographs. did.
　X線ロッキングカーブによりGaN(002)ピークのFWHMを測定した結果は、以下の表１に示すように、成長温度780℃の場合は41.8arcmin、成長温度700℃の場合は83.0arcminであり、実施例１及び２で得られたGaN層におけるGaN(002)ピークのFWHMに対して２～４倍大きい値となった。このことから、本発明における第２のバッファ層の形成が、GaN層の平坦性だけでなく、結晶性改善にも有効であることが判明した。 As shown in Table 1 below, the FWHM of the GaN (002) peak measured by the X-ray rocking curve is 41.8 arcmin when the growth temperature is 780 ° C, and 83.0arcmin when the growth temperature is 700 ° C. The GaN (002) peak in the GaN layers obtained in Examples 1 and 2 was 2 to 4 times larger than the FWHM. From this, it was found that the formation of the second buffer layer in the present invention is effective not only for the flatness of the GaN layer but also for improving the crystallinity.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
（比較例２）
　図１０に、文献E.G.Villora et al., Appl. Phys. Lett., 90 (2007) 234102.に記載された光デバイス用基板の断面TEM像を示す。図中、aで示されるGa2O3基板部材表面の窒化層の上に第２のバッファ層を形成することなく、厚さ400nm程度のGaN層が形成されている。このGaN層のうちcで示される上層部分には積層欠陥がほとんど存在しないが、窒化層直上のbで示される厚さ約200nmの部分には水平方向の積層欠陥が大量に形成されていることが確認される。 (Comparative Example 2)
FIG. 10 shows a cross-sectional TEM image of an optical device substrate described in the document EGVillora et al., Appl. Phys. Lett., 90 (2007) 234102. In the drawing, a GaN layer having a thickness of about 400 nm is formed on the nitride layer on the surface of the Ga 2 O 3 substrate member indicated by a without forming the second buffer layer. Almost no stacking faults exist in the upper layer part indicated by c in this GaN layer, but a large amount of stacking faults in the horizontal direction are formed in the part of the thickness of about 200 nm indicated by b immediately above the nitride layer. Is confirmed.
　これに対し、図６に示した実施例１の断面TEM像では、積層欠陥自体がないGaN層が厚さ100nm程度の第２のバッファ層の上に形成されている。
　すなわち、第２のバッファ層を形成しない場合には、積層欠陥をなくすために厚さ約200nmのGaN成長が必要になるのに対し、Ga2O3基板部材表面の窒化層の上に厚さ100nm程度のGaN成長により第２のバッファ層を形成することで、積層欠陥のないGaN層が得られる。従って、生産効率、製造コストなどの観点から、第２のバッファ層の形成が有効であることがわかる。 On the other hand, in the cross-sectional TEM image of Example 1 shown in FIG. 6, the GaN layer without the stacking fault itself is formed on the second buffer layer having a thickness of about 100 nm.
That is, when the second buffer layer is not formed, GaN growth with a thickness of about 200 nm is necessary to eliminate stacking faults, whereas the thickness is formed on the nitride layer on the surface of the Ga 2 O 3 substrate member. By forming the second buffer layer by GaN growth of about 100 nm, a GaN layer free from stacking faults can be obtained. Therefore, it can be seen that the formation of the second buffer layer is effective from the viewpoint of production efficiency, manufacturing cost, and the like.
　本発明によれば、酸化ガリウム単結晶基板部材を窒化処理して第１のバッファ層を形成した後、所定の成長温度より低い温度で窒化ガリウムからなる第２のバッファ層を成長形成し、さらに、第２のバッファ層の表面上に所定の成長温度で窒化ガリウム層を成長形成するので、酸化ガリウム基板部材を用いながらも表面平坦性に優れ且つ結晶品質性に優れた窒化ガリウム層を有する光デバイス用基板を得ることができる。 According to the present invention, after forming the first buffer layer by nitriding the gallium oxide single crystal substrate member, the second buffer layer made of gallium nitride is grown at a temperature lower than a predetermined growth temperature, and Since the gallium nitride layer is grown on the surface of the second buffer layer at a predetermined growth temperature, the light having a gallium nitride layer having excellent surface flatness and excellent crystal quality while using a gallium oxide substrate member A device substrate can be obtained.

Claims (7)

  1. 　酸化ガリウム単結晶基板部材を備えると共に表面層として所定の成長温度で成長形成された窒化ガリウム層を有する光デバイス用基板において、
    　前記酸化ガリウム単結晶基板部材の表面上に窒化処理により形成された六方晶窒化ガリウムからなる第１のバッファ層と、
    　前記第１のバッファ層の表面上に所定の成長温度より低い温度で成長形成された六方晶窒化ガリウムからなる第２のバッファ層と、
    　前記第２のバッファ層の表面上に前記所定の成長温度で成長形成された六方晶窒化ガリウム層と
    　を備えたことを特徴とする光デバイス用基板。     In a substrate for an optical device comprising a gallium oxide single crystal substrate member and having a gallium nitride layer grown at a predetermined growth temperature as a surface layer,
    A first buffer layer made of hexagonal gallium nitride formed by nitriding on the surface of the gallium oxide single crystal substrate member;
    A second buffer layer made of hexagonal gallium nitride grown on the surface of the first buffer layer at a temperature lower than a predetermined growth temperature;
    An optical device substrate comprising: a hexagonal gallium nitride layer grown on the surface of the second buffer layer at the predetermined growth temperature.
  2. 　酸化ガリウム単結晶基板部材を備えると共に表面層として所定の成長温度で成長形成された窒化ガリウム層を有する光デバイス用基板の製造方法において、
    　前記酸化ガリウム単結晶基板部材を窒化処理することにより前記酸化ガリウム単結晶基板部材の表面上に六方晶窒化ガリウムからなる第１のバッファ層を形成し、
    　前記第１のバッファ層の表面上に所定の成長温度より低い温度で六方晶窒化ガリウムからなる第２のバッファ層を成長形成し、
    　前記第２のバッファ層の表面上に前記所定の成長温度で六方晶窒化ガリウム層を成長形成する
    　ことを特徴とする光デバイス用基板の製造方法。     In a method for manufacturing an optical device substrate comprising a gallium oxide single crystal substrate member and having a gallium nitride layer grown at a predetermined growth temperature as a surface layer,
    Forming a first buffer layer of hexagonal gallium nitride on the surface of the gallium oxide single crystal substrate member by nitriding the gallium oxide single crystal substrate member;
    A second buffer layer made of hexagonal gallium nitride is grown on the surface of the first buffer layer at a temperature lower than a predetermined growth temperature;
    A method of manufacturing a substrate for an optical device, comprising: growing a hexagonal gallium nitride layer on the surface of the second buffer layer at the predetermined growth temperature.
  3. 　前記第１のバッファ層は、高周波窒素プラズマを用いた窒化処理により形成される請求項２に記載の光デバイス用基板の製造方法。 3. The method for manufacturing a substrate for an optical device according to claim 2, wherein the first buffer layer is formed by nitriding using high-frequency nitrogen plasma.
  4. 　前記窒化処理は、前記酸化ガリウム単結晶基板部材の温度300～400℃、窒化時間60～100分により行われる請求項３に記載の光デバイス用基板の製造方法。 4. The method for manufacturing an optical device substrate according to claim 3, wherein the nitriding treatment is performed at a temperature of 300 to 400 ° C. and a nitriding time of 60 to 100 minutes of the gallium oxide single crystal substrate member.
  5. 　前記第２のバッファ層及び前記窒化ガリウム層は、高周波分子線エピタキシー法により成長形成される請求項２乃至請求項４のいずれかに記載の光デバイス用基板の製造方法。 5. The method for manufacturing an optical device substrate according to claim 2, wherein the second buffer layer and the gallium nitride layer are grown by high-frequency molecular beam epitaxy.
  6. 　前記第２のバッファ層は、前記酸化ガリウム単結晶基板部材の温度480～520℃、成長時間5～15分で成長形成される請求項５に記載の光デバイス用基板の製造方法。 6. The method of manufacturing a substrate for an optical device according to claim 5, wherein the second buffer layer is grown at a temperature of 480 to 520 ° C. and a growth time of 5 to 15 minutes of the gallium oxide single crystal substrate member.
  7. 　前記窒化ガリウム層は、前記酸化ガリウム単結晶基板部材の温度650～750℃、成長時間50～90分で成長形成される請求項５または請求項６に記載の光デバイス用基板の製造方法。 The method for manufacturing a substrate for an optical device according to claim 5 or 6, wherein the gallium nitride layer is grown and formed at a temperature of 650 to 750 ° C and a growth time of 50 to 90 minutes of the gallium oxide single crystal substrate member.
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