WO2018123153A1 - Method for producing group 13 element nitride - Google Patents

Method for producing group 13 element nitride Download PDF

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WO2018123153A1
WO2018123153A1 PCT/JP2017/032816 JP2017032816W WO2018123153A1 WO 2018123153 A1 WO2018123153 A1 WO 2018123153A1 JP 2017032816 W JP2017032816 W JP 2017032816W WO 2018123153 A1 WO2018123153 A1 WO 2018123153A1
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gallium nitride
crystal
group
seed crystal
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崇行 平尾
佳範 磯田
卓 野口
哲哉 内川
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日本碍子株式会社
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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
    • C30B19/00—Liquid-phase epitaxial-layer growth
    • C30B19/02—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux
    • C30B19/04—Liquid-phase epitaxial-layer growth using molten solvents, e.g. flux the solvent being a component of the crystal composition
    • 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
    • C30B19/00—Liquid-phase epitaxial-layer growth
    • C30B19/12—Liquid-phase 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
    • 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
    • C30B29/38—Nitrides

Definitions

  • the present invention relates to a method for producing a group 13 element nitride crystal.
  • the present invention is, for example, a technical field that requires high quality, for example, a high color rendering blue LED, a blue-violet laser for high-speed and high-density optical memory, which is said to be a next-generation light source that replaces a fluorescent lamp, and an inverter for a hybrid vehicle. It can use for the power device etc. which are used for.
  • the flux method is one of liquid phase methods.
  • gallium nitride the temperature required for crystal growth of gallium nitride can be relaxed to about 800 ° C. and the pressure can be reduced to several MPa by using metallic sodium as the flux. .
  • nitrogen gas is dissolved in a mixed melt of metallic sodium and metallic gallium, and gallium nitride becomes supersaturated and grows as crystals.
  • dislocations are less likely to occur than in a gas phase method, so that high-quality gallium nitride having a low dislocation density can be obtained.
  • Patent Document 1 As a method for growing a high-quality gallium nitride crystal having a low dislocation density by the flux method, a film is formed by increasing the molar ratio of Ga in the melt (Ga / (Ga + Na)) (Patent Document 1). 2) is known. Specifically, the group 13 element nitride crystal is grown while controlling the flow of the melt by setting the Ga ratio in the melt to 22 to 32 mol% and applying a temperature gradient to the melt.
  • Patent Document 3 proposes growing a gallium nitride crystal on a sapphire substrate having an off angle of 0.5 to 2 ° in the a-axis direction.
  • dislocation density can be reduced by increasing the Ga ratio in the melt and increasing the grain size by controlling the flow of the melt.
  • a grain boundary is likely to be generated between grains, and inclusions are likely to be contained along the grain boundaries, and the inclusion may be a problem as a macro structural defect.
  • the “grain boundary” means a discontinuous boundary between a crystal grain and an adjacent crystal grain. In the process of crystal growth from the liquid phase, impurities (foreign matter) tend to remain at the grain boundaries.
  • inclusion refers to a heterogeneous phase composed of melt components involved in grain boundaries. Inclusions are sometimes referred to as vacuoles.
  • the dislocation density of the group 13 element nitride crystal is reduced by controlling the off-angle of the seed crystal, and the inclusion flow is also suppressed by controlling the flow of the flux.
  • the larger the diameter of the crystal the more difficult it is to control the flow over the entire surface of the substrate, resulting in the problem that inclusions remain on the outer periphery of the crystal.
  • the inclusion that was generated first was suppressed during the growth by controlling the flow of the flux, the grain boundary remained after that, and there was a problem that cracks were likely to occur starting from the grain boundary due to thermal stress after growth.
  • An object of the present invention is to bring a seed crystal composed of a group 13 element nitride into contact with a melt containing a group 13 metal and an alkali metal, and introduce a nitrogen gas into the melt while introducing a group 13 on the main surface of the seed crystal.
  • a seed crystal composed of a group 13 element nitride it is to lower the dislocation density of the crystal, suppress the inclusion remaining, and suppress cracks originating from the grain boundary due to thermal stress.
  • a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt.
  • a method of growing elemental nitride crystals The normal to the main surface of the seed crystal has an off angle of 0.4 to 5.0 ° in the ⁇ 11-20> direction with respect to the ⁇ 0001> direction of the seed crystal, When the total amount of the group 13 metal and the alkali metal is 100 mol%, the ratio of the group 13 metal is 24 mol% or more and 38 mol% or less.
  • a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt.
  • the dislocation density of the crystal can be lowered, the remaining inclusions can be suppressed, and cracks originating from grain boundaries due to thermal stress can be suppressed.
  • Macroscopic structural defects such as inclusions and cracks can be achieved by increasing the group 13 metal ratio in the melt as in Patent Documents 1 and 2 or by growing on a seed crystal having a large off angle as described in Patent Document 3. Tends to be contained. Therefore, it has not been easily predicted that inclusions and cracks can be suppressed while maintaining a low dislocation density by the present invention combining these two.
  • FIG. 3 is a longitudinal sectional view of a seed crystal 18.
  • FIG. 2 is an optical micrograph of the gallium nitride crystal obtained in Example 1. The result of CL (cathode luminescence) observation of the gallium nitride crystal obtained in Example 1 is shown.
  • 3 is an optical micrograph of the gallium nitride crystal obtained in Example 2. The result of CL observation of the gallium nitride crystal obtained in Example 2 is shown.
  • 4 is an optical micrograph of a gallium nitride crystal obtained in Example 3. The result of CL observation of the gallium nitride crystal obtained in Example 3 is shown.
  • 4 is an optical micrograph of a gallium nitride crystal obtained in Example 4.
  • Example 4 The result of CL observation of the gallium nitride crystal obtained in Example 4 is shown.
  • 6 is an optical micrograph of the gallium nitride crystal obtained in Example 5.
  • the result of CL observation of the gallium nitride crystal obtained in Example 5 is shown.
  • 6 is an optical micrograph of the gallium nitride crystal obtained in Example 6.
  • the result of CL observation of the gallium nitride crystal obtained in Example 6 is shown.
  • 2 is an optical micrograph of a gallium nitride crystal obtained in Comparative Example 1.
  • the result of CL observation of the gallium nitride crystal obtained in Comparative Example 1 is shown.
  • 4 is an optical micrograph of a gallium nitride crystal obtained in Comparative Example 2.
  • a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 element is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt.
  • Grow nitride crystals are sequentially described.
  • the seed crystal may be a seed crystal film formed on a support substrate, or may be a self-supporting seed crystal substrate. Further, a buffer layer or an underlayer may be provided between the support substrate and the seed crystal film.
  • the material constituting the support substrate is not limited, but sapphire, AlN template, gallium nitride template, gallium nitride free-standing substrate, silicon single crystal, SiC single crystal, MgO single crystal , Spinel (MgAl 2 O 4 ), LiAlO 2 , LiGaO 2 , LaAlO 3 , LaGaO 3 , NdGaO 3 and other perovskite complex oxides, SCAM (ScAlMgO 4 ).
  • cubic perovskite structure composite oxides (1) and (2) can be used.
  • the group 13 element of the group 13 element nitride constituting the group 13 element nitride crystal on the seed crystal, the underlayer, and the seed crystal is a group 13 element according to a periodic table established by IUPAC.
  • the group 13 element is specifically gallium, aluminum, indium, thallium, or the like.
  • This group 13 element nitride is particularly preferably gallium nitride, aluminum nitride, or gallium aluminum nitride.
  • the additive include carbon, low melting point metals (tin, bismuth, silver, gold) and high melting point metals (transition metals such as iron, manganese, titanium, and chromium).
  • the seed crystal production method is not particularly limited, but metal organic chemical vapor deposition (MOCVD) method, metal hydride chemical method, vapor deposition method (HVPE), pulsed excitation deposition (PXD) method, MBE method, sublimation method, etc.
  • MOCVD metal organic chemical vapor deposition
  • HVPE vapor deposition method
  • PXD pulsed excitation deposition
  • MBE sublimation method
  • liquid phase method such as the gas phase method and the flux method.
  • the normal to the main surface of the seed crystal has an off angle of 0.4 to 5.0 ° in the ⁇ 11-20> direction with respect to the ⁇ 0001> direction of the seed crystal. That is, as shown in FIG. 1, the normal to the main surface 18a of the seed crystal 18 has an off angle of 0.4 to 5.0 ° in the ⁇ 11-20> direction with respect to the ⁇ 0001> direction of the seed crystal.
  • the off angle is more preferably 0.5 ° or more, and further preferably 2.0 ° or less.
  • a group 13 element nitride film is formed on the main surface 18a by a flux method. Note that there may be a supporting substrate not shown in FIG.
  • the group 13 element nitride constituting the seed crystal is a hexagonal crystal
  • this crystal orientation will be described.
  • the c-plane that is perpendicular to the c-axis is the (0001) plane
  • [-2110] direction, [-12-10] direction, [11-20] direction, [2-1-10] direction, [1-210] direction, and [-1-120] direction are Since they are all equivalent from the viewpoint of symmetry, they are expressed as ⁇ 11-20> directions.
  • the group 13 element nitride crystal is grown by bringing the main surface of the seed crystal into contact with the melt. At this time, the melt contains a Group 13 metal and an alkali metal.
  • the group 13 element is gallium, aluminum, indium, thallium, or the like, and sodium is particularly preferable as the alkali metal.
  • a functional element can be obtained by forming a predetermined functional layer on the surface of the group 13 element nitride crystal.
  • a functional layer may be a single layer or a plurality of layers.
  • it can be used for white LEDs with high luminance and high color rendering, blue-violet laser disks for high-speed and high-density optical memory, power devices for inverters for hybrid vehicles, and the like.
  • Example 1 Gallium nitride substrate fabrication
  • Gallium nitride (GaN) crystals were grown. Specifically, a 4 ⁇ m-thick gallium nitride film was formed on a ⁇ 2 inch sapphire substrate by a vapor phase method to obtain a seed crystal substrate.
  • the normal to the main surface of the seed crystal made of gallium nitride crystal was set to an off angle of 2.0 ° in the ⁇ 11-20> direction with respect to the ⁇ 0001> direction of the seed crystal.
  • the crucible was put into a stainless steel inner container, and further put into a stainless steel outer container that could accommodate it, and closed with a container lid with a nitrogen introduction pipe.
  • This outer container was placed on a turntable installed in a heating unit in a crystal manufacturing apparatus that had been baked in advance, and the pressure-resistant container was covered and sealed.
  • the solidified sodium metal in the crucible was removed, and the grown gallium nitride substrate was recovered. There was no crack in the gallium nitride after the growth. Sapphire was removed from the recovered gallium nitride substrate by laser lift-off. The front and back surfaces of the self-supporting gallium nitride substrate were polished.
  • the polished gallium nitride substrate was cut vertically, the cut surface was polished and observed with an optical microscope (200 times). As a result, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 2).
  • the surface of the polished gallium nitride substrate was subjected to dislocation density measurement with a scanning electron microscope (SEM) equipped with a cathode luminescence (CL) observation detector.
  • SEM scanning electron microscope
  • CL cathode luminescence
  • Example 2 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 2, Ga / Ga + Na (mol%) was 30 mol%, and the off-angle was 0.4 °. After the growth, there was no crack in the gallium nitride.
  • Example 3 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 2, Ga / Ga + Na (mol%) was 30 mol%, and the off angle was 5.0 °. After the growth, there was no crack in the gallium nitride.
  • Example 4 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 4, Ga / Ga + Na (mol%) was 24 mol%, and the off angle was 2.0 °. After the growth, there was no crack in the gallium nitride.
  • Example 5 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) was 38 mol%, and the off angle was 2.0 °. After the growth, there was no crack in the gallium nitride.
  • Example 6 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol%, the off-angle is 2.0 °, and the size of the seed crystal substrate is 6 inches. After the growth, there was no crack in the gallium nitride.
  • Example 1 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol%, and the off angle is 0.3 °.
  • the dislocation density was 3.9 ⁇ 10 5 / cm 2 in the field of 80 ⁇ m ⁇ 105 ⁇ m (see FIG. 15).
  • Example 2 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol% and the off-angle is 6.0 °.
  • Example 4 In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 40 mol%, and the off angle is 2.0 °.

Abstract

The normal vector to the main surface of a seed crystal has an off angle of 0.4-5.0° in the <11-20> direction with respect to the <0001> direction of the seed crystal, and the proportion of a group 13 metal is 24-38 mol% when the total amount of the group 13 metal and alkali metals in a melt is 100 mol%.

Description

１３族元素窒化物の製造方法Method for producing group 13 element nitride
　本発明は、１３族元素窒化物結晶の製造方法に関するものである。本発明は、例えば、高品質であることが要求される技術分野、例えば蛍光灯を置き換える次世代光源といわれている高演色性の青色ＬＥＤや高速高密度光メモリ用青紫レーザ、ハイブリッド自動車用のインバータに用いるパワーデバイスなどに用いることができる。 The present invention relates to a method for producing a group 13 element nitride crystal. The present invention is, for example, a technical field that requires high quality, for example, a high color rendering blue LED, a blue-violet laser for high-speed and high-density optical memory, which is said to be a next-generation light source that replaces a fluorescent lamp, and an inverter for a hybrid vehicle. It can use for the power device etc. which are used for.
　フラックス法は、液相法の一つであり、窒化ガリウムの場合、フラックスとして金属ナトリウムを用いることで窒化ガリウムの結晶成長に必要な温度を８００℃程度、圧力を数ＭＰａに緩和することができる。具体的には、金属ナトリウムと金属ガリウムとの混合融液中に窒素ガスが溶解し、窒化ガリウムが過飽和状態になって結晶として成長する。こうした液相法では、気相法に比べて転位が発生しにくいため、転位密度の低い高品質な窒化ガリウムを得ることができる。 The flux method is one of liquid phase methods. In the case of gallium nitride, the temperature required for crystal growth of gallium nitride can be relaxed to about 800 ° C. and the pressure can be reduced to several MPa by using metallic sodium as the flux. . Specifically, nitrogen gas is dissolved in a mixed melt of metallic sodium and metallic gallium, and gallium nitride becomes supersaturated and grows as crystals. In such a liquid phase method, dislocations are less likely to occur than in a gas phase method, so that high-quality gallium nitride having a low dislocation density can be obtained.
　フラックス法によって、転位密度の低い高品質な窒化ガリウム結晶を育成する方法としては、融液中のGaのモル比率（Ga/(Ga+Na)）を高くして成膜する方法（特許文献１、２）が知られている。具体的には、融液中のＧａ比を22～32mol%とし、融液に温度勾配をつけて融液の流れを制御しながら１３族元素窒化物結晶を育成する。 As a method for growing a high-quality gallium nitride crystal having a low dislocation density by the flux method, a film is formed by increasing the molar ratio of Ga in the melt (Ga / (Ga + Na)) (Patent Document 1). 2) is known. Specifically, the group 13 element nitride crystal is grown while controlling the flow of the melt by setting the Ga ratio in the melt to 22 to 32 mol% and applying a temperature gradient to the melt.
　また、特許文献３には、a軸方向に0.5～2°のオフ角を有するサファイア基板上に窒化ガリウム結晶を成長させることを提案している。 Patent Document 3 proposes growing a gallium nitride crystal on a sapphire substrate having an off angle of 0.5 to 2 ° in the a-axis direction.
特許第5651480号Patent No. 5651480 特許第5651481号Patent No. 5651481 特許第5897790号Japanese Patent No. 5877790
　特許文献１、２記載の方法では、融液中のGa比を高くし、かつ融液の流れ制御でグレイン（結晶粒）サイズを大きくして転位密度を低減する事ができる。しかし、この方法では、グレインとグレインとの間に粒界が発生しやすく、さらに粒界に沿ってインクルージョンが含有されやすくなり、インクルージョンがマクロな構造欠陥として問題になる場合がある。
　なお、「粒界」とは、結晶粒と隣り合う結晶粒との間の不連続な境界をいう。液相から結晶成長する過程においては、粒界に不純物（異物）が残留しやすい。「インクルージョン」とは、粒界に巻き込まれた融液成分からなる異相のことをいう。インクルージョンは液胞と称されることもある。 In the methods described in Patent Documents 1 and 2, dislocation density can be reduced by increasing the Ga ratio in the melt and increasing the grain size by controlling the flow of the melt. However, in this method, a grain boundary is likely to be generated between grains, and inclusions are likely to be contained along the grain boundaries, and the inclusion may be a problem as a macro structural defect.
The “grain boundary” means a discontinuous boundary between a crystal grain and an adjacent crystal grain. In the process of crystal growth from the liquid phase, impurities (foreign matter) tend to remain at the grain boundaries. “Inclusion” refers to a heterogeneous phase composed of melt components involved in grain boundaries. Inclusions are sometimes referred to as vacuoles.
　特許文献３では、種結晶のオフ角制御により１３族元素窒化物結晶の転位密度の低下を実現し、フラックスの流れ制御によってインクルージョンの抑制ももたらしている。しかし、結晶が大口径になるほど、基板全面での流れの制御が困難となり、結晶の外周にインクルージョンが残存するという問題が生じた。また、初めに発生したインクルージョンをフラックスの流れ制御によって成長途中で抑制させても、その後に粒界は残り、育成後に熱応力で粒界を起点にクラックが発生しやすいという問題が生じた。 In Patent Document 3, the dislocation density of the group 13 element nitride crystal is reduced by controlling the off-angle of the seed crystal, and the inclusion flow is also suppressed by controlling the flow of the flux. However, the larger the diameter of the crystal, the more difficult it is to control the flow over the entire surface of the substrate, resulting in the problem that inclusions remain on the outer periphery of the crystal. Moreover, even if the inclusion that was generated first was suppressed during the growth by controlling the flow of the flux, the grain boundary remained after that, and there was a problem that cracks were likely to occur starting from the grain boundary due to thermal stress after growth.
　本発明の課題は、１３族元素窒化物からなる種結晶を、１３族金属とアルカリ金属とを含む融液に接触させ、融液に窒素ガスを導入しながら種結晶の主面上に１３族元素窒化物結晶を成長させるのに際して、結晶の転位密度を低くし、インクルージョンの残存を抑制し、かつ熱応力による粒界を起点とするクラックを抑制することである。 An object of the present invention is to bring a seed crystal composed of a group 13 element nitride into contact with a melt containing a group 13 metal and an alkali metal, and introduce a nitrogen gas into the melt while introducing a group 13 on the main surface of the seed crystal. In growing an element nitride crystal, it is to lower the dislocation density of the crystal, suppress the inclusion remaining, and suppress cracks originating from the grain boundary due to thermal stress.
　本発明は、１３族元素窒化物からなる種結晶を、１３族金属とアルカリ金属とを含む融液に接触させ、前記融液に窒素ガスを導入しながら前記種結晶の主面上に１３族元素窒化物結晶を成長させる方法であって、
　前記種結晶の前記主面に対する法線が前記種結晶の＜０００１＞方向に対して＜１１－２０＞方向に０．４～５．０°のオフ角を有しており、前記融液における前記１３族金属と前記アルカリ金属との合計量を１００ｍｏｌ％としたとき、前記１３族金属の割合を２４ｍｏｌ％以上、３８ｍｏｌ％以下とすることを特徴とする。 In the present invention, a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt. A method of growing elemental nitride crystals,
The normal to the main surface of the seed crystal has an off angle of 0.4 to 5.0 ° in the <11-20> direction with respect to the <0001> direction of the seed crystal, When the total amount of the group 13 metal and the alkali metal is 100 mol%, the ratio of the group 13 metal is 24 mol% or more and 38 mol% or less.
　本発明によれば、１３族元素窒化物からなる種結晶を、１３族金属とアルカリ金属とを含む融液に接触させ、融液に窒素ガスを導入しながら種結晶の主面上に１３族元素窒化物結晶を成長させるのに際して、結晶の転位密度を低くし、インクルージョンの残存を抑制し、かつ熱応力による粒界を起点とするクラックを抑制することができる。 According to the present invention, a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt. When growing an element nitride crystal, the dislocation density of the crystal can be lowered, the remaining inclusions can be suppressed, and cracks originating from grain boundaries due to thermal stress can be suppressed.
　しかも、融液の流れに依存せずに、上記効果が得られるので、大口径基板においても全面均一な窒化ガリウム結晶を作製する事が可能となる。 In addition, since the above-described effect can be obtained without depending on the flow of the melt, it is possible to produce a uniform gallium nitride crystal over the entire surface of a large-diameter substrate.
　特許文献１、２のように融液中の１３族金属比率を高くする方法も、特許文献３記載のようにオフ角の大きな種結晶上に育成する方法でも、インクルージョンやクラックといったマクロな構造欠陥が含有されやすい傾向にある。ゆえに、これら両者を組合せた本発明によって、低い転位密度を維持しつつ、インクルージョンやクラックを抑制できることは容易に予測できなかった。 Macroscopic structural defects such as inclusions and cracks can be achieved by increasing the group 13 metal ratio in the melt as in Patent Documents 1 and 2 or by growing on a seed crystal having a large off angle as described in Patent Document 3. Tends to be contained. Therefore, it has not been easily predicted that inclusions and cracks can be suppressed while maintaining a low dislocation density by the present invention combining these two.
種結晶１８の縦断面図である。3 is a longitudinal sectional view of a seed crystal 18. FIG. 実施例１で得られた窒化ガリウム結晶の光学顕微鏡写真である。2 is an optical micrograph of the gallium nitride crystal obtained in Example 1. 実施例１で得られた窒化ガリウム結晶のＣＬ（カソードルミネッセンス）観察の結果を示す。The result of CL (cathode luminescence) observation of the gallium nitride crystal obtained in Example 1 is shown. 実施例２で得られた窒化ガリウム結晶の光学顕微鏡写真である。3 is an optical micrograph of the gallium nitride crystal obtained in Example 2. 実施例２で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Example 2 is shown. 実施例３で得られた窒化ガリウム結晶の光学顕微鏡写真である。4 is an optical micrograph of a gallium nitride crystal obtained in Example 3. 実施例３で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Example 3 is shown. 実施例４で得られた窒化ガリウム結晶の光学顕微鏡写真である。4 is an optical micrograph of a gallium nitride crystal obtained in Example 4. 実施例４で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Example 4 is shown. 実施例５で得られた窒化ガリウム結晶の光学顕微鏡写真である。6 is an optical micrograph of the gallium nitride crystal obtained in Example 5. 実施例５で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Example 5 is shown. 実施例６で得られた窒化ガリウム結晶の光学顕微鏡写真である。6 is an optical micrograph of the gallium nitride crystal obtained in Example 6. 実施例６で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Example 6 is shown. 比較例１で得られた窒化ガリウム結晶の光学顕微鏡写真である。2 is an optical micrograph of a gallium nitride crystal obtained in Comparative Example 1. 比較例１で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Comparative Example 1 is shown. 比較例２で得られた窒化ガリウム結晶の光学顕微鏡写真である。4 is an optical micrograph of a gallium nitride crystal obtained in Comparative Example 2. 比較例２で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Comparative Example 2 is shown. 比較例３で得られた窒化ガリウム結晶の光学顕微鏡写真である。4 is an optical micrograph of a gallium nitride crystal obtained in Comparative Example 3. 比較例３で得られた窒化ガリウム結晶のＣＬ観察の結果を示す。The result of CL observation of the gallium nitride crystal obtained in Comparative Example 3 is shown.
　以下、本発明の実施形態について順次説明する。
　本発明では、１３族元素窒化物からなる種結晶を、１３族金属とアルカリ金属とを含む融液に接触させ、前記融液に窒素ガスを導入しながら種結晶の主面上に１３族元素窒化物結晶を成長させる。 Hereinafter, embodiments of the present invention will be sequentially described.
In the present invention, a seed crystal composed of a group 13 element nitride is brought into contact with a melt containing a group 13 metal and an alkali metal, and a group 13 element is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt. Grow nitride crystals.
　ここで、種結晶は、支持基板上に形成された種結晶膜であってよく、あるいは自立した種結晶基板であってもよい。また、支持基板と種結晶膜との間にはバッファ層や下地層が設けられていて良い。 Here, the seed crystal may be a seed crystal film formed on a support substrate, or may be a self-supporting seed crystal substrate. Further, a buffer layer or an underlayer may be provided between the support substrate and the seed crystal film.
　支持基板上に種結晶膜を形成する場合には、支持基板を構成する材質は限定されないが、サファイア、ＡｌＮテンプレート、窒化ガリウムテンプレート、窒化ガリウム自立基板、シリコン単結晶、ＳｉＣ単結晶、ＭｇＯ単結晶、スピネル（ＭｇＡｌ２Ｏ４）、ＬｉＡｌＯ２、ＬｉＧａＯ２、ＬａＡｌＯ３，ＬａＧａＯ３，ＮｄＧａＯ３等のペロブスカイト型複合酸化物、ＳＣＡＭ（ＳｃＡｌＭｇＯ４）を例示できる。また組成式〔Ａ１－ｙ（Ｓｒ１－ｘＢａｘ）ｙ〕〔（Ａｌ１－ｚＧａｚ）１－ｕ・Ｄｕ〕Ｏ３（Ａは、希土類元素である；Ｄは、ニオブおよびタンタルからなる群より選ばれた一種以上の元素である；ｙ＝０．３～０．９８；ｘ＝０～１；ｚ＝０～１；ｕ＝０．１５～０．４９；ｘ＋ｚ＝０．１～２）の立方晶系のペロブスカイト構造複合酸化物も使用できる。 When the seed crystal film is formed on the support substrate, the material constituting the support substrate is not limited, but sapphire, AlN template, gallium nitride template, gallium nitride free-standing substrate, silicon single crystal, SiC single crystal, MgO single crystal , Spinel (MgAl 2 O 4 ), LiAlO 2 , LiGaO 2 , LaAlO 3 , LaGaO 3 , NdGaO 3 and other perovskite complex oxides, SCAM (ScAlMgO 4 ). In addition, the composition formula [A 1-y (Sr 1-x Ba x ) y ] [(Al 1-z Ga z ) 1-u · D u ] O 3 (A is a rare earth element; D is niobium and One or more elements selected from the group consisting of tantalum; y = 0.3 to 0.98; x = 0 to 1; z = 0 to 1; u = 0.15 to 0.49; x + z = 0 Also, cubic perovskite structure composite oxides (1) and (2) can be used.
　種結晶、下地層、および種結晶上の１３族元素窒化物結晶を構成する１３族元素窒化物の１３族元素とは、ＩＵＰＡＣが策定した周期律表による第１３族元素のことである。１３族元素は、具体的にはガリウム、アルミニウム、インジウム、タリウム等である。この１３族元素窒化物は、特に好ましくは、窒化ガリウム、窒化アルミニウム、窒化ガリウムアルミニウムである。また、添加剤としては、炭素や、低融点金属（錫、ビスマス、銀、金）、高融点金属（鉄、マンガン、チタン、クロムなどの遷移金属）が挙げられる。 The group 13 element of the group 13 element nitride constituting the group 13 element nitride crystal on the seed crystal, the underlayer, and the seed crystal is a group 13 element according to a periodic table established by IUPAC. The group 13 element is specifically gallium, aluminum, indium, thallium, or the like. This group 13 element nitride is particularly preferably gallium nitride, aluminum nitride, or gallium aluminum nitride. Examples of the additive include carbon, low melting point metals (tin, bismuth, silver, gold) and high melting point metals (transition metals such as iron, manganese, titanium, and chromium).
　種結晶の製法は特に限定されないが、有機金属化学気相成長（ＭＯＣＶＤ： Metal Organic Chemical Vapor Deposition）法、ハイドライド気相成長（ＨＶＰＥ）法、パルス励起堆積（ＰＸＤ）法、ＭＢＥ法、昇華法などの気相法、フラックス法などの液相法を例示できる。 The seed crystal production method is not particularly limited, but metal organic chemical vapor deposition (MOCVD) method, metal hydride chemical method, vapor deposition method (HVPE), pulsed excitation deposition (PXD) method, MBE method, sublimation method, etc. Examples of the liquid phase method such as the gas phase method and the flux method.
　本発明においては、種結晶の主面に対する法線が種結晶の＜０００１＞方向に対して＜１１－２０＞方向に０．４～５．０°のオフ角を有している。すなわち、図１に示すように、種結晶１８の主面１８ａに対する法線が、種結晶の＜０００１＞方向に対して＜１１－２０＞方向に０．４～５．０°のオフ角を有している。本発明の観点からは、このオフ角は、０．５°以上が更に好ましく、また２．０°以下が更に好ましい。
　この主面１８ａ上にフラックス法によって１３族元素窒化物を成膜する。なお、図１に図示しない支持基板があってもよい。 In the present invention, the normal to the main surface of the seed crystal has an off angle of 0.4 to 5.0 ° in the <11-20> direction with respect to the <0001> direction of the seed crystal. That is, as shown in FIG. 1, the normal to the main surface 18a of the seed crystal 18 has an off angle of 0.4 to 5.0 ° in the <11-20> direction with respect to the <0001> direction of the seed crystal. Have. From the viewpoint of the present invention, the off angle is more preferably 0.5 ° or more, and further preferably 2.0 ° or less.
A group 13 element nitride film is formed on the main surface 18a by a flux method. Note that there may be a supporting substrate not shown in FIG.
　種結晶を構成する１３族元素窒化物は六方晶であるので、この結晶方位について説明する。六方晶において、ｃ軸に垂直な面であるｃ面は（０００１）面、－ｃ面は（０００－１）面であるが、これらは対称性の観点から等価なので、｛０００１｝面と表記される。また、［０－１１０］方向、［－１０１０］方向、［－１１００］方向、［０１－１０］方向、［１０－１０］方向及び［１－１００］方向は、対称性の観点から全て等価なので、＜１－１００＞方向と表記される。更に、［－２１１０］方向、［－１２－１０］方向、［１１－２０］方向、［２－１－１０］方向、［１－２１０］方向及び［－１－１２０］方向は、これらは対称性の観点から全て等価なので、＜１１－２０＞方向と表記される。 Since the group 13 element nitride constituting the seed crystal is a hexagonal crystal, this crystal orientation will be described. In the hexagonal crystal, the c-plane that is perpendicular to the c-axis is the (0001) plane, and the -c plane is the (000-1) plane. Is done. [0-110] direction, [-1010] direction, [-1100] direction, [01-10] direction, [10-10] direction and [1-100] direction are all equivalent from the viewpoint of symmetry. Therefore, it is expressed as <1-100> direction. Furthermore, the [-2110] direction, [-12-10] direction, [11-20] direction, [2-1-10] direction, [1-210] direction, and [-1-120] direction are Since they are all equivalent from the viewpoint of symmetry, they are expressed as <11-20> directions.
　上記した種結晶の主面を融液に接触させることで、１３族元素窒化物結晶を育成する。この際、融液は、１３族金属とアルカリ金属とを含有する。１３族元素は、ガリウム、アルミニウム、インジウム、タリウム等であり、アルカリ金属としてはナトリウムが特に好ましい。 The group 13 element nitride crystal is grown by bringing the main surface of the seed crystal into contact with the melt. At this time, the melt contains a Group 13 metal and an alkali metal. The group 13 element is gallium, aluminum, indium, thallium, or the like, and sodium is particularly preferable as the alkali metal.
　１３族元素窒化物結晶の表面上に所定の機能層を形成することで、機能素子を得ることができる。こうした機能層は、単一層であってよく、複数層であってよい。また、機能としては、高輝度・高演色性の白色ＬＥＤや高速高密度光メモリ用青紫レーザディスク、ハイブリッド自動車用のインバータ用のパワーデバイスなどに用いることができる。 A functional element can be obtained by forming a predetermined functional layer on the surface of the group 13 element nitride crystal. Such a functional layer may be a single layer or a plurality of layers. As functions, it can be used for white LEDs with high luminance and high color rendering, blue-violet laser disks for high-speed and high-density optical memory, power devices for inverters for hybrid vehicles, and the like.
（実施例１）
（窒化ガリウム基板作製）
　窒化ガリウム（ＧａＮ）結晶を育成した。
　具体的には、φ２インチのサファイア基板上に気相法で厚さ４μｍの窒化ガリウムを成膜し、種結晶基板を得た。ただし、窒化ガリウム結晶からなる種結晶の主面に対する法線が、種結晶の＜０００１＞方向に対して＜１１－２０＞方向に２．０°のオフ角をなすようにした。 Example 1
(Gallium nitride substrate fabrication)
Gallium nitride (GaN) crystals were grown.
Specifically, a 4 μm-thick gallium nitride film was formed on a φ2 inch sapphire substrate by a vapor phase method to obtain a seed crystal substrate. However, the normal to the main surface of the seed crystal made of gallium nitride crystal was set to an off angle of 2.0 ° in the <11-20> direction with respect to the <0001> direction of the seed crystal.
　この種結晶基板を、窒素雰囲気のグローブボックス内でアルミナ坩堝の底に水平に配置した。次に、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）＝３０ｍｏｌ％となるように金属ガリウムと金属ナトリウムを坩堝内に充填し、アルミナ板で蓋をした。その坩堝をステンレス製内容器に入れ、さらにそれを収納できるステンレス製外容器に入れて、窒素導入パイプの付いた容器蓋で閉じた。この外容器を、予め真空ベークしてある結晶製造装置内の加熱部に設置されている回転台の上に配置し、耐圧容器に蓋をして密閉した。 This seed crystal substrate was placed horizontally on the bottom of an alumina crucible in a nitrogen atmosphere glove box. Next, metal gallium and metal sodium were filled in the crucible so that Ga / Ga + Na (mol%) = 30 mol%, and the lid was covered with an alumina plate. The crucible was put into a stainless steel inner container, and further put into a stainless steel outer container that could accommodate it, and closed with a container lid with a nitrogen introduction pipe. This outer container was placed on a turntable installed in a heating unit in a crystal manufacturing apparatus that had been baked in advance, and the pressure-resistant container was covered and sealed.
　次いで、耐圧容器内を真空ポンプにて０．１Pa以下まで真空引きした。続いて、上段ヒータ、中段ヒータ及び下段ヒータを調節して加熱空間の温度を８７０℃になるように加熱しながら、４．０ＭＰａまで窒素ガスボンベから窒素ガスを導入し、外容器を中心軸周りに２０ｒｐｍの速度で一定周期の時計回りと反時計回りで回転させた。加速時間＝１２秒、保持時間＝６００秒、減速時間＝１２秒、停止時間＝０．５秒とした。そして、この状態で４０時間保持した。その後、室温まで自然冷却して大気圧にまで減圧した後、耐圧容器の蓋を開けて中から坩堝を取り出した。坩堝の中の固化した金属ナトリウムを除去し、成長した窒化ガリウム基板を回収した。育成後に窒化ガリウムにクラックはなかった。回収した窒化ガリウム基板からレーザーリフトオフでサファイアを除去した。自立化した窒化ガリウム基板表面および裏面を研磨加工した。 Next, the inside of the pressure vessel was evacuated to 0.1 Pa or less with a vacuum pump. Subsequently, while adjusting the upper, middle and lower heaters so that the temperature of the heating space is 870 ° C., nitrogen gas is introduced from the nitrogen gas cylinder up to 4.0 MPa, and the outer container is moved around the central axis. It was rotated clockwise and counterclockwise at a constant cycle at a speed of 20 rpm. Acceleration time = 12 seconds, holding time = 600 seconds, deceleration time = 12 seconds, stop time = 0.5 seconds. And it hold | maintained for 40 hours in this state. Then, after naturally cooling to room temperature and reducing the pressure to atmospheric pressure, the lid of the pressure vessel was opened and the crucible was taken out from the inside. The solidified sodium metal in the crucible was removed, and the grown gallium nitride substrate was recovered. There was no crack in the gallium nitride after the growth. Sapphire was removed from the recovered gallium nitride substrate by laser lift-off. The front and back surfaces of the self-supporting gallium nitride substrate were polished.
（評価）
　研磨加工した窒化ガリウム基板を垂直に切断し、切断面を研磨加工して光学顕微鏡（２００倍）で観察した。その結果、窒化ガリウム結晶内部にボイドは確認されず、均質な窒化ガリウム結晶が成長していることが確認された（図２参照）。 (Evaluation)
The polished gallium nitride substrate was cut vertically, the cut surface was polished and observed with an optical microscope (200 times). As a result, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 2).
　また、研磨加工した窒化ガリウム基板の表面を、カソードルミネッセンス（ＣＬ）観察検出器付きの走査電子顕微鏡（ＳＥＭ）で転位密度測定を行った。窒化ガリウム基板をＣＬ観察すると、転位箇所が発光せずに黒点（ダークスポット）として観察される。そのダークスポット密度を計測する事により、転位密度が算出される。８０μｍ×１０５μｍ視野を観察した結果、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図３参照）。 The surface of the polished gallium nitride substrate was subjected to dislocation density measurement with a scanning electron microscope (SEM) equipped with a cathode luminescence (CL) observation detector. When the gallium nitride substrate is observed with CL, dislocation sites are observed as black spots (dark spots) without emitting light. By measuring the dark spot density, the dislocation density is calculated. As a result of observing an 80 μm × 105 μm visual field, no dark spots were observed, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (see FIG. 3).
（実施例２）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、実施例２においては、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３０ｍｏｌ％であり、前記オフ角が０．４°であった。育成後、窒化ガリウムにクラックはなかった。 (Example 2)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 2, Ga / Ga + Na (mol%) was 30 mol%, and the off-angle was 0.4 °. After the growth, there was no crack in the gallium nitride.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部にボイドは確認されず、均質な窒化ガリウム結晶が成長していることが確認された（図４参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図５参照）。 As a result of optical microscope observation, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 4). Further, as a result of CL observation of the gallium nitride substrate, no dark spots were observed in the 80 μm × 105 μm visual field, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 5). reference).
（実施例３）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、実施例２においては、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３０ｍｏｌ％であり、前記オフ角が５．０°であった。育成後、窒化ガリウムにクラックはなかった。 (Example 3)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 2, Ga / Ga + Na (mol%) was 30 mol%, and the off angle was 5.0 °. After the growth, there was no crack in the gallium nitride.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部に細かいボイドが僅かに見られた（図６参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図７参照）。 As a result of observation with an optical microscope, slight voids were slightly observed inside the gallium nitride crystal (see FIG. 6). Further, as a result of CL observation of the gallium nitride substrate, no dark spot was observed in the 80 μm × 105 μm field of view, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 7). reference).
（実施例４）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、実施例４においては、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が２４ｍｏｌ％であり、前記オフ角が２．０°であった。育成後、窒化ガリウムにクラックはなかった。 Example 4
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, in Example 4, Ga / Ga + Na (mol%) was 24 mol%, and the off angle was 2.0 °. After the growth, there was no crack in the gallium nitride.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部にボイドは確認されず、均質な窒化ガリウム結晶が成長していることが確認された（図８参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図９参照）。 As a result of observation with an optical microscope, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 8). Further, as a result of CL observation of the gallium nitride substrate, no dark spots were observed in the 80 μm × 105 μm field of view, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 9). reference).
（実施例５）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３８ｍｏｌ％であり、前記オフ角が２．０°であった。育成後、窒化ガリウムにクラックはなかった。 (Example 5)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) was 38 mol%, and the off angle was 2.0 °. After the growth, there was no crack in the gallium nitride.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部にボイドは確認されず、均質な窒化ガリウム結晶が成長していることが確認された（図１０参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図１１参照）。 As a result of observation with an optical microscope, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 10). Further, as a result of CL observation of the gallium nitride substrate, no dark spots were observed in the 80 μm × 105 μm field of view, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 11). reference).
（実施例６）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３０ｍｏｌ％であり、前記オフ角が２．０°であり、種結晶基板のサイズが６インチである。育成後、窒化ガリウムにクラックはなかった。 (Example 6)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol%, the off-angle is 2.0 °, and the size of the seed crystal substrate is 6 inches. After the growth, there was no crack in the gallium nitride.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部にボイドは確認されず、均質な窒化ガリウム結晶が成長していることが確認された（図１２参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図１３参照）。 As a result of observation with an optical microscope, no void was confirmed inside the gallium nitride crystal, and it was confirmed that a homogeneous gallium nitride crystal was growing (see FIG. 12). Further, as a result of CL observation of the gallium nitride substrate, no dark spots were observed in the 80 μm × 105 μm visual field, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 13). reference).
（比較例１）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３０ｍｏｌ％であり、前記オフ角が０．３°である。 (Comparative Example 1)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol%, and the off angle is 0.3 °.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部に数十μｍのボイドが確認された（図１４参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、転位密度は３．９×１０５/ｃｍ２であった（図１５参照）。 As a result of observation with an optical microscope, voids of several tens of μm were confirmed inside the gallium nitride crystal (see FIG. 14). As a result of CL observation of the gallium nitride substrate, the dislocation density was 3.9 × 10 5 / cm 2 in the field of 80 μm × 105 μm (see FIG. 15).
（比較例２）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が３０ｍｏｌ％であり、前記オフ角が６．０°である。 (Comparative Example 2)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 30 mol% and the off-angle is 6.0 °.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部に数～数十μｍのボイドが確認された（図１６参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図１７参照）。 As a result of observation with an optical microscope, voids of several to several tens of μm were confirmed inside the gallium nitride crystal (see FIG. 16). Further, as a result of CL observation of the gallium nitride substrate, no dark spot was observed in the 80 μm × 105 μm field of view, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 17). reference).
（比較例３）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が２２ｍｏｌ％であり、前記オフ角が２．０°である。 (Comparative Example 3)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 22 mol% and the off-angle is 2.0 °.
　光学顕微鏡観察の結果、窒化ガリウム結晶内部に数～数十μｍのボイドが確認された（図１８参照）。また、窒化ガリウム基板をＣＬ観察した結果、８０μｍ×１０５μｍ視野において、ダークスポットは１つも観察されず、転位密度は少なくとも１．２×１０４/ｃｍ２未満である事が確認された（図１９参照）。 As a result of observation with an optical microscope, voids of several to several tens of μm were confirmed inside the gallium nitride crystal (see FIG. 18). Further, as a result of CL observation of the gallium nitride substrate, no dark spots were observed in the 80 μm × 105 μm field of view, and it was confirmed that the dislocation density was at least less than 1.2 × 10 4 / cm 2 (FIG. 19). reference).
（比較例４）
　実施例１と同様にして、各例の窒化ガリウム結晶を育成し、実施例１と同様に評価した。ただし、Ｇａ／Ｇａ＋Ｎａ（ｍｏｌ％）が４０ｍｏｌ％であり、前記オフ角が２．０°である。 (Comparative Example 4)
In the same manner as in Example 1, gallium nitride crystals in each example were grown and evaluated in the same manner as in Example 1. However, Ga / Ga + Na (mol%) is 40 mol%, and the off angle is 2.0 °.
　結晶育成後の基板を回収したところ。窒化ガリウムは成長していたが、結晶同士が会合しておらず、六角錘形状のグレインの集合体となっており、均質な窒化ガリウム基板が得られなかった。このため、研磨加工ができなかったので、光学顕微鏡観察およびＣＬ観察による転位密度測定は行わなかった。
　以上の測定結果を表１にまとめる。 The substrate after crystal growth is recovered. Although gallium nitride was growing, crystals were not associated with each other, and it was an aggregate of hexagonal pyramidal grains, and a homogeneous gallium nitride substrate could not be obtained. For this reason, since polishing could not be performed, dislocation density measurement by optical microscope observation and CL observation was not performed.
The above measurement results are summarized in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001

Claims (2)

  1. 　１３族元素窒化物からなる種結晶を、１３族金属とアルカリ金属とを含む融液に接触させ、前記融液に窒素ガスを導入しながら前記種結晶の主面上に１３族元素窒化物結晶を成長させる方法であって、
    　前記種結晶の前記主面に対する法線が前記種結晶の＜０００１＞方向に対して＜１１－２０＞方向に０．４～５．０°のオフ角を有しており、前記融液における前記１３族金属と前記アルカリ金属との合計量を１００ｍｏｌ％としたとき、前記１３族金属の割合を２４ｍｏｌ％以上、３８ｍｏｌ％以下とすることを特徴とする、１３族元素窒化物の製造方法。
          A seed crystal composed of a Group 13 element nitride is brought into contact with a melt containing a Group 13 metal and an alkali metal, and a Group 13 element nitride crystal is formed on the main surface of the seed crystal while introducing nitrogen gas into the melt. A method of growing
    The normal to the main surface of the seed crystal has an off angle of 0.4 to 5.0 ° in the <11-20> direction with respect to the <0001> direction of the seed crystal, The method for producing a group 13 element nitride, characterized in that the ratio of the group 13 metal is 24 mol% or more and 38 mol% or less when the total amount of the group 13 metal and the alkali metal is 100 mol%.
  2. 　前記１３族金属がガリウムであり、前記アルカリ金属がナトリウムを含むことを特徴とする、請求項１記載の方法。 The method of claim 1, wherein the group 13 metal is gallium and the alkali metal includes sodium.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009051686A (en) * 2007-08-24 2009-03-12 Sumitomo Electric Ind Ltd Method for growing group iii nitride crystal
JP5651480B2 (en) * 2009-01-23 2015-01-14 日本碍子株式会社 Method for producing group 3B nitride crystals
JP5897790B2 (en) * 2009-10-22 2016-03-30 日本碍子株式会社 Group 3B nitride single crystal and process for producing the same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009051686A (en) * 2007-08-24 2009-03-12 Sumitomo Electric Ind Ltd Method for growing group iii nitride crystal
JP5651480B2 (en) * 2009-01-23 2015-01-14 日本碍子株式会社 Method for producing group 3B nitride crystals
JP5897790B2 (en) * 2009-10-22 2016-03-30 日本碍子株式会社 Group 3B nitride single crystal and process for producing the same

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