JP5864998B2

JP5864998B2 - Method for growing β-Ga 2 O 3 single crystal

Info

Publication number: JP5864998B2
Application number: JP2011224243A
Authority: JP
Inventors: 公祥輿; 信也渡辺; 公平佐々木; 優山岡; 建和氏家
Original assignee: Tamura Corp; Koha Co Ltd
Current assignee: Tamura Corp; Koha Co Ltd
Priority date: 2011-10-11
Filing date: 2011-10-11
Publication date: 2016-02-17
Anticipated expiration: 2031-10-11
Also published as: JP2013082587A

Description

本発明は、β−Ｇａ_２Ｏ_３系単結晶の成長方法に関し、特に、双晶化を抑えることのできるβ−Ｇａ_２Ｏ_３系単結晶の成長方法に関する。 The present invention relates to a method of growing a _β-Ga 2 _{O 3} single crystal, in particular, it relates to method of growing _β-Ga 2 _{O 3} single crystal that can suppress the twinning.

従来のβ−Ｇａ_２Ｏ_３系単結晶の成長方法として、ＦＺ（Floating Zone）法を用いた双晶化やクラッキングを抑えることのできる方法が知られている（例えば、特許文献１参照）。特許文献１に記載の方法によれば、β−Ｇａ_２Ｏ_３系単結晶をそのａ軸、ｂ軸、又はｃ軸と平行な方向に成長させることにより、双晶化やクラッキングを減少させることができる。 As a conventional method for growing a β-Ga ₂ O ₃ -based single crystal, a method capable of suppressing twinning and cracking using an FZ (Floating Zone) method is known (see, for example, Patent Document 1). According to the method described in Patent Document 1, it is possible to reduce twinning and cracking by growing a β-Ga ₂ O ₃ single crystal in a direction parallel to the a-axis, b-axis, or c-axis. Can do.

特開２００４−２６２６８４号公報JP 2004-262684 A

しかし、実際には、特許文献１に記載の方法により必ずしも十分な効果が得られるとは限らず、特に、ｂ軸に沿った方向にβ−Ｇａ_２Ｏ_３系単結晶を成長させた場合には、実用可能なレベルのβ−Ｇａ_２Ｏ_３系単結晶を得るために十分な程度に双晶化を抑えることは難しい。 However, in practice, a sufficient effect is not always obtained by the method described in Patent Document 1, and in particular, when a β-Ga ₂ O ₃ single crystal is grown in a direction along the b-axis. However, it is difficult to suppress twinning to a sufficient extent to obtain a β-Ga ₂ O ₃ single crystal at a practical level.

したがって、本発明の目的は、双晶化を効果的に抑えることのできるβ−Ｇａ_２Ｏ_３系単結晶の成長方法を提供することである。 Accordingly, an object of the present invention is to provide a method for growing a β-Ga ₂ O ₃ single crystal capable of effectively suppressing twinning.

本発明の一態様は、上記目的を達成するために、［１］〜［９］のβ−Ｇａ_２Ｏ_３系
単結晶の成長方法を提供する。 In order to achieve the above object, one embodiment of the present invention provides a method for growing a β-Ga ₂ O ₃ single crystal of [1] to [ 9 ].

［１］β−Ｇａ_２Ｏ_３系単結晶をその（１０１）面に平行な方向（ｂ軸＜０１０＞方向に対してプラスマイナス１０°の範囲内の方向を除く）に成長させ、前記（１０１）面内における＜１０−１＞方向と前記方向とのなす角度φ（０°≦φ＜９０°）が９０°未満である、β−Ｇａ_２Ｏ_３系単結晶の成長方法。 [1] A β-Ga ₂ O ₃ based single crystal is grown in a direction parallel to the (101) plane (excluding directions in the range of plus or minus 10 ° with respect to the b-axis <010> direction). 101) A method for growing a β-Ga ₂ O ₃ single crystal, wherein an angle φ (0 ° ≦ φ <90 °) between the <10-1> direction in the plane and the direction is less than 90 ° .

［２］前記角度φは４５°以下である、前記［１］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [2] The β-Ga ₂ O ₃ single crystal growth method according to [1], wherein the angle φ is 45 ° or less.

［３］前記角度φは２０°以下である、前記［２］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [3] The β-Ga ₂ O ₃ single crystal growth method according to [2], wherein the angle φ is 20 ° or less.

［４］前記角度φは０°である、前記［３］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [4] The β-Ga ₂ O ₃ single crystal growth method according to [3], wherein the angle φ is 0 °.

［５］前記β−Ｇａ_２Ｏ_３系単結晶は前記（１０１）面を主面とする平板状の結晶である、前記［１］〜［４］のいずれか１つに記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [5] The β-Ga ₂ O ₃ -based single crystal is a plate-like crystal having the (101) plane as a main surface, and the β-Ga according to any one of [1] to [4]. _A method for growing a ₂ O ₃ single crystal.

［６］ＥＦＧ法により前記β−Ｇａ_２Ｏ_３系単結晶を成長させる、前記［５］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [6] EFG method by growing the _β-Ga 2 _{O 3} single crystal growing method of the _β-Ga 2 _{O 3} single crystal according to [5].

［７］β−Ｇａ_２Ｏ_３系単結晶をその（１００）面に垂直な直線となす角度が５５．２°以内の方向（ａ軸＜１００＞方向に対してプラスマイナス１０°の範囲内の方向を除く）に成長させる、β−Ｇａ_２Ｏ_３系単結晶の成長方法。 [7] An angle between the β-Ga ₂ O ₃ single crystal and a straight line perpendicular to the (100) plane is within 55.2 ° ( within ± 10 ° with respect to the a-axis <100> direction) A method of growing a β-Ga ₂ O ₃ single crystal.

［８］β−Ｇａ_２Ｏ_３系単結晶をその（１００）面に垂直な直線となす角度が０°の方向に成長させる、前記［７］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [8] _β-Ga 2 a _{O 3} system single crystal angle between a line perpendicular to the (100) plane is grown in the direction of 0 °, the _{_{[7] β-Ga 2 O}} 3 system single crystal according to Growth method.

［９］ＦＺ法により前記β−Ｇａ_２Ｏ_３系単結晶を成長させる、前記［７］又は［８］に記載のβ−Ｇａ_２Ｏ_３系単結晶の成長方法。 [9] FZ method by growing the _β-Ga 2 _{O 3} system single crystal, the [7] or [8] method of growing _β-Ga 2 _{O 3} system single crystal according to.

本発明によれば、双晶化を効果的に抑えることのできるβ−Ｇａ_２Ｏ_３系単結晶の成長方法を提供することができる。 According to the present invention can provide a method for growing a β-Ga ₂ O ₃ single crystal that can suppress the twinning effectively.

第１の実施の形態に係るＥＦＧ結晶製造装置の一部の垂直断面図Partial vertical sectional view of the EFG crystal manufacturing apparatus according to the first embodiment β−Ｇａ_２Ｏ_３系単結晶の成長中の様子を表す斜視図A perspective view showing a state during growth of a β-Ga ₂ O ₃ single crystal β−Ｇａ_２Ｏ_３系結晶の単位格子を示す図It shows a unit cell of the _β-Ga 2 _{O 3} based crystals β−Ｇａ_２Ｏ_３系単結晶の成長中に発生する双晶の概念図Conceptual diagram of twins generated during growth of β-Ga ₂ O ₃ single crystal （ａ）（１０１）面が結晶成長方向に平行である場合のβ−Ｇａ_２Ｏ_３系単結晶の＜１０−１＞方向と成長方向の関係を表す概念図、（ｂ）β−Ｇａ_２Ｏ_３系単結晶の単位格子における＜１０−１＞方向、（１０１）面、及び（１００）面(A) Conceptual diagram showing the relationship between the <10-1> direction of the β-Ga ₂ O ₃ -based single crystal and the growth direction when the (101) plane is parallel to the crystal growth direction, (b) β-Ga ₂ <10-1> direction, (101) plane, and (100) plane in the unit cell of O ₃ single crystal β−Ｇａ_２Ｏ_３系単結晶の双晶化度と角度φとの関係を表すグラフThe graph showing the relationship between the twinning degree of β-Ga ₂ O ₃ single crystal and the angle φ （ａ）、（ｂ）第２の実施の形態に係るβ−Ｇａ_２Ｏ_３系単結晶の結晶成長方向の範囲を表す概念図(A), a conceptual diagram representing the (b) crystal growth direction in the range of a second embodiment in accordance with β-Ga ₂ O ₃ single crystal

〔第１の実施の形態〕
本実施の形態においては、ＥＦＧ（Edge-defined film-fed growth）法によりβ−Ｇａ_２Ｏ_３系単結晶を成長させる。 [First Embodiment]
In the present embodiment, a β-Ga ₂ O ₃ single crystal is grown by an EFG (Edge-defined film-fed growth) method.

図１は、本実施の形態に係るＥＦＧ結晶製造装置の一部の垂直断面図である。このＥＦＧ結晶製造装置１０は、β−Ｇａ_２Ｏ_３系融液１２を受容するルツボ１３と、このルツボ１３内に設置されたスリット１４Ａを有するダイ１４と、スリット１４Ａの開口１４Ｂを除くルツボ１３の上面を閉塞する蓋１５と、β−Ｇａ_２Ｏ_３種結晶（以下、「種結晶」という）２０を保持する種結晶保持具２１と、種結晶保持具２１を昇降可能に支持するシャフト２２とを有する。 FIG. 1 is a vertical sectional view of a part of the EFG crystal manufacturing apparatus according to the present embodiment. The EFG crystal manufacturing apparatus 10 includes a crucible 13 that receives a β-Ga ₂ O ₃ -based melt 12, a die 14 having a slit 14 A installed in the crucible 13, and a crucible 13 excluding an opening 14 B of the slit 14 A. , A seed crystal holder 21 that holds a β-Ga ₂ O ₃ seed crystal (hereinafter referred to as “seed crystal”) 20, and a shaft 22 that supports the seed crystal holder 21 so as to be movable up and down. And have.

ルツボ１３は、β−Ｇａ_２Ｏ_３系粉末を溶解させて得られたβ−Ｇａ_２Ｏ_３系融液１２を収容する。ルツボ１３は、β−Ｇａ_２Ｏ_３系融液１２を収容しうる耐熱性を有するイリジウム等の金属材料からなる。 The crucible 13 contains the β-Ga ₂ O ₃ melt 12 obtained by dissolving the β-Ga ₂ O ₃ powder. The crucible 13 is made of a metal material such as iridium having heat resistance that can accommodate the β-Ga ₂ O ₃ melt 12.

ダイ１４は、β−Ｇａ_２Ｏ_３系融液１２を毛細管現象により上昇させるためのスリット１４Ａを有する。 The die 14 has a slit 14A for raising the β-Ga ₂ O ₃ -based melt 12 by capillary action.

蓋１５は、ルツボ１３から高温のβ−Ｇａ_２Ｏ_３系融液１２が蒸発することを防止し、さらにスリット１４Ａの上面以外の部分にβ−Ｇａ_２Ｏ_３系融液１２の蒸気が付着することを防ぐ。 The lid 15 prevents the high-temperature β-Ga ₂ O ₃ melt 12 from evaporating from the crucible 13, and the vapor of the β-Ga ₂ O ₃ melt 12 adheres to a portion other than the upper surface of the slit 14A. To prevent.

種結晶２０を下降させて毛細管現象で上昇したβ−Ｇａ_２Ｏ_３系融液１２に接触させ、β−Ｇａ_２Ｏ_３系融液１２と接触した種結晶２０を引き上げることにより、平板状のβ−Ｇａ_２Ｏ_３系単結晶２５を成長させる。種結晶２０の底面の幅はダイ１４の長手方向の幅よりも小さく、β−Ｇａ_２Ｏ_３系単結晶２５は種結晶２０の引き上げに伴ってダイ１４の長手方向に拡張しながら成長する（肩拡げ過程）。β−Ｇａ_２Ｏ_３系単結晶２５の結晶方位は種結晶２０の結晶方位と等しく、β−Ｇａ_２Ｏ_３系単結晶２５の結晶方位を制御するためには、例えば、種結晶２０の底面の面方位及び水平面内の角度を調整する。 The seed crystal 20 is lowered and brought into contact with the β-Ga ₂ O ₃ melt 12 raised by capillary action, and the seed crystal 20 in contact with the β-Ga ₂ O ₃ melt 12 is pulled up, whereby a plate-like shape is obtained. A β-Ga ₂ O ₃ single crystal 25 is grown. The width of the bottom surface of the seed crystal 20 is smaller than the width in the longitudinal direction of the die 14, and the β-Ga ₂ O ₃ single crystal 25 grows while expanding in the longitudinal direction of the die 14 as the seed crystal 20 is pulled up ( Shoulder expansion process). crystal orientation of the _β-Ga 2 _{O 3} single crystal 25 is equal to the crystal orientation of the seed crystal 20, in order to control the crystal orientation of the _β-Ga 2 _{O 3} single crystal 25 is, for example, the bottom surface of the seed crystal 20 Adjust the plane orientation and angle in the horizontal plane.

図２は、β−Ｇａ_２Ｏ_３系単結晶の成長中の様子を表す斜視図である。図２中の面２６は、スリット１４Ａのスリット方向と平行なβ−Ｇａ_２Ｏ_３系単結晶２５の主面である。成長させたβ−Ｇａ_２Ｏ_３系単結晶２５を切り出してβ−Ｇａ_２Ｏ_３系基板を形成する場合は、β−Ｇａ_２Ｏ_３系基板の所望の主面の面方位にβ−Ｇａ_２Ｏ_３系単結晶２５の面２６の面方位を一致させる。例えば、（１０１）面を主面とするβ−Ｇａ_２Ｏ_３系基板を形成する場合は、面２６の面方位を（１０１）とする。また、成長させたβ−Ｇａ_２Ｏ_３系単結晶２５は、新たなβ−Ｇａ_２Ｏ_３系単結晶を成長させるための種結晶として用いることができる。 FIG. 2 is a perspective view illustrating a state during the growth of the β-Ga ₂ O ₃ single crystal. A surface 26 in FIG. 2 is a main surface of the β-Ga ₂ O ₃ single crystal 25 parallel to the slit direction of the slit 14A. If cut out _β-Ga 2 _{O 3} single crystal 25 is grown to form a _β-Ga 2 _{O 3} system board, the plane orientation of the desired major surface of the _β-Ga 2 _{O 3} based substrate beta-Ga The plane orientation of the face 26 of the ₂ O ₃ system single crystal 25 is matched. For example, when a β-Ga ₂ O ₃ -based substrate having the (101) plane as the main surface is formed, the plane orientation of the plane 26 is set to (101). The grown β-Ga ₂ O ₃ single crystal 25 can be used as a seed crystal for growing a new β-Ga ₂ O ₃ single crystal.

β−Ｇａ_２Ｏ_３系単結晶２５及び種結晶２０は、β−Ｇａ_２Ｏ_３単結晶、又は、Ｃｕ、Ａｇ、Ｚｎ、Ｃｄ、Ａｌ、Ｉｎ、Ｓｉ、Ｇｅ、Ｓｎ、Ｈｆ、Ｍｇ等の元素が添加されたβ−Ｇａ_２Ｏ_３単結晶である。 The β-Ga ₂ O ₃ -based single crystal 25 and the seed crystal 20 are a β-Ga ₂ O ₃ single crystal, or Cu, Ag, Zn, Cd, Al, In, Si, Ge, Sn, Hf, Mg, etc. It is a β-Ga ₂ O ₃ single crystal to which an element is added.

図３は、β−Ｇａ_２Ｏ_３系結晶の単位格子を示す。図３中の単位格子２がβ−Ｇａ_２Ｏ_３系結晶の単位格子である。β−Ｇａ_２Ｏ_３系結晶は単斜晶系に属するβ-ガリア構造を有し、不純物を含まないβ−Ｇａ_２Ｏ_３結晶の典型的な格子定数はａ_０＝１２．２３Å、ｂ_０＝３．０４Å、ｃ_０＝５．８０Å、α＝γ＝９０°、β＝１０３．８°である。 FIG. 3 shows a unit cell of a β-Ga ₂ O ₃ based crystal. A unit cell 2 in FIG. 3 is a unit cell of a β-Ga ₂ O ₃ based crystal. The β-Ga ₂ O ₃ crystal has a β-gallia structure belonging to a monoclinic system, and a typical lattice constant of a β-Ga ₂ O ₃ crystal containing no impurities is a ₀ = 12.23．, b ₀ = 3.04Å, c ₀ = 5.80Å, α = γ = 90 °, β = 103.8 °.

図４は、β−Ｇａ_２Ｏ_３系単結晶の成長中に発生する双晶の概念図である。双晶は、鏡面対称な２つのβ−Ｇａ_２Ｏ_３系結晶からなる。β−Ｇａ_２Ｏ_３系結晶の双晶の対称面（双晶面）は、（１００）面である。ＥＦＧ法によりβ−Ｇａ_２Ｏ_３系単結晶を成長させる場合、結晶成長開始後の結晶の肩拡げ過程において双晶が発生しやすい。 FIG. 4 is a conceptual diagram of twins generated during the growth of a β-Ga ₂ O ₃ single crystal. The twin crystal is composed of two mirror-symmetric β-Ga ₂ O ₃ -based crystals. The twin symmetry plane (twin plane) of the β-Ga ₂ O ₃ based crystal is the (100) plane. When a β-Ga ₂ O ₃ single crystal is grown by the EFG method, twins are likely to be generated in the shoulder expansion process of the crystal after the start of crystal growth.

この双晶面となる（１００）面がβ−Ｇａ_２Ｏ_３系単結晶２５の成長方向（種結晶２０の引き上げ方向）に平行である場合に、β−Ｇａ_２Ｏ_３系単結晶２５が双晶化しやすくなる傾向がある。反対に、β−Ｇａ_２Ｏ_３系単結晶２５の成長方向と（１００）面とのなす角度が直角に近いほど、β−Ｇａ_２Ｏ_３系単結晶２５の成長時の双晶化を抑えることができる。 When the (100) plane serving as the twin plane is parallel to the growth direction of the β-Ga ₂ O ₃ single crystal 25 (the pulling direction of the seed crystal 20), the β-Ga ₂ O ₃ single crystal 25 is There is a tendency to twinning easily. On the contrary, the twinning during the growth of the β-Ga ₂ O ₃ single crystal 25 is suppressed as the angle between the growth direction of the β-Ga ₂ O ₃ single crystal 25 and the (100) plane is closer to a right angle. be able to.

図５（ａ）は、（１０１）面が結晶成長方向に平行である場合のβ−Ｇａ_２Ｏ_３系単結晶２５の＜１０−１＞方向と成長方向の関係を表す概念図である。図５（ｂ）には、β−Ｇａ_２Ｏ_３系単結晶２５の単位格子２における＜１０−１＞方向、（１０１）面、及び（１００）面を示す。図５（ａ）においては、（１０１）面が紙面に平行である。φは、β−Ｇａ_２Ｏ_３系単結晶２５の（１０１）面内において＜１０−１＞方向と結晶成長方向（鉛直方向）とのなす角度である。 FIG. 5A is a conceptual diagram showing the relationship between the <10-1> direction of the β-Ga ₂ O ₃ single crystal 25 and the growth direction when the (101) plane is parallel to the crystal growth direction. FIG. 5B shows the <10-1> direction, the (101) plane, and the (100) plane in the unit cell 2 of the β-Ga ₂ O ₃ -based single crystal 25. In FIG. 5A, the (101) plane is parallel to the paper surface. φ is an angle between the <10-1> direction and the crystal growth direction (vertical direction) in the (101) plane of the β-Ga ₂ O ₃ single crystal 25.

ここで、角度φが９０°であるとき、β−Ｇａ_２Ｏ_３系単結晶２５の成長方向と（１００）面は平行であり、角度φが０°であるとき、β−Ｇａ_２Ｏ_３系単結晶２５の成長方向と（１００）面とのなす角度は最も直角に近くなる。つまり、角度φが０°に近いほど、β−Ｇａ_２Ｏ_３系単結晶２５の成長時の双晶化を効果的に抑えることができる。 Here, when the angle φ is 90 °, the growth direction of the β-Ga ₂ O ₃ single crystal 25 and the (100) plane are parallel, and when the angle φ is 0 °, β-Ga ₂ O ₃ The angle formed by the growth direction of the system single crystal 25 and the (100) plane is closest to the right angle. That is, as the angle φ is closer to 0 °, twinning during the growth of the β-Ga ₂ O ₃ single crystal 25 can be effectively suppressed.

そのため、本実施の形態においては、角度φ（０°≦φ＜９０°）の範囲は少なくとも９０°未満、好ましくは４５°以下、より好ましくは２０°以下、最も好ましくは０°である。例えば、β−Ｇａ_２Ｏ_３系単結晶２５の面２６を（１０１）面とした場合、この条件を満たすことにより、β−Ｇａ_２Ｏ_３系単結晶２５から（１０１）面を主面とする双晶の少ないβ−Ｇａ_２Ｏ_３系基板を切り出すことができる。 Therefore, in the present embodiment, the range of the angle φ (0 ° ≦ φ <90 °) is at least less than 90 °, preferably 45 ° or less, more preferably 20 ° or less, and most preferably 0 °. For example, when the surface 26 of the β-Ga ₂ O ₃ -based single crystal 25 is the (101) surface, by satisfying this condition, the (101) surface is defined as the main surface from the β-Ga ₂ O ₃ -based single crystal 25. It is possible to cut a β-Ga ₂ O ₃ -based substrate with few twins.

図６は、β−Ｇａ_２Ｏ_３系単結晶の双晶化度と角度φとの関係を表すグラフである。図６の縦軸は、（１００）面を双晶面として結晶構造が反転した領域の平均密度（面２６上の成長方向と垂直な方向の１ｃｍ当たりの平均数）を表す。横軸は、角度φを表す。φ＝９０°のときは、反転領域が１ｃｍ当たり平均２７．８本存在し、φ＝４５°のときは、反転領域が１ｃｍ当たり平均９本存在し、φ＝０°のときは、反転領域が存在しない。 FIG. 6 is a graph showing the relationship between the twinning degree of the β-Ga ₂ O ₃ single crystal and the angle φ. The vertical axis in FIG. 6 represents the average density (average number per cm in the direction perpendicular to the growth direction on the surface 26) of the region where the crystal structure is inverted with the (100) plane as the twin plane. The horizontal axis represents the angle φ. When φ = 90 °, there are an average of 27.8 inversion regions per cm, when φ = 45 °, an average of 9 inversion regions per cm, and when φ = 0 °, the inversion regions Does not exist.

図６に示されるように、φ＝９０°、すなわちβ−Ｇａ_２Ｏ_３系単結晶２５の＜１０−１＞方向が結晶成長方向に対して垂直であるときに最も双晶が多く、φ＝０°、すなわちβ−Ｇａ_２Ｏ_３系単結晶２５の＜１０−１＞方向が結晶成長方向に対して平行であるときに最も双晶が少ない。これは、β−Ｇａ_２Ｏ_３系単結晶２５の成長方向と（１００）面が、φ＝９０°のときに平行であり、φ＝０°のときに最も直角に近くなることによると考えられる。 As shown in FIG. 6, when φ = 90 °, that is, when the <10-1> direction of the β-Ga ₂ O ₃ -based single crystal 25 is perpendicular to the crystal growth direction, there are most twins, = 0 °, that is, there are few twins when the <10-1> direction of the β-Ga ₂ O ₃ single crystal 25 is parallel to the crystal growth direction. This is considered to be because the growth direction of the β-Ga ₂ O ₃ single crystal 25 and the (100) plane are parallel when φ = 90 ° and are closest to the right angle when φ = 0 °. It is done.

なお、第１の実施の形態においては、ＥＦＧ法を用いてβ−Ｇａ_２Ｏ_３系単結晶２５を成長させたが、ＣＺ（Czochralski）法、ＦＺ（Floating Zone）法等の他の結晶成長方法を用いた場合であってもβ−Ｇａ_２Ｏ_３系単結晶２５の双晶化を効果的に抑えることができる。それらの場合も、β−Ｇａ_２Ｏ_３系単結晶２５の結晶方位と成長方向の関係はＥＦＧ法を用いる場合と同様である。 In the first embodiment, the β-Ga ₂ O ₃ single crystal 25 is grown by using the EFG method. However, other crystal growth methods such as a CZ (Czochralski) method and an FZ (Floating Zone) method are used. Even when the method is used, twinning of the β-Ga ₂ O ₃ single crystal 25 can be effectively suppressed. In those cases, the relationship between the crystal orientation and the growth direction of the β-Ga ₂ O ₃ single crystal 25 is the same as that in the case of using the EFG method.

〔第２の実施の形態〕
第２の実施の形態は、結晶の成長方向の範囲が第１の実施の形態と異なる。第１の実施の形態と同様の点については、説明を省略又は簡略化する。 [Second Embodiment]
The second embodiment is different from the first embodiment in the range of the crystal growth direction. The description of the same points as in the first embodiment will be omitted or simplified.

図７（ａ）、（ｂ）は、第２の実施の形態に係るβ−Ｇａ_２Ｏ_３系単結晶の結晶成長方向の範囲を表す概念図である。図７（ａ）においては、β−Ｇａ_２Ｏ_３系単結晶のｂ軸及びｃ軸が紙面に平行である。図７（ｂ）においては、β−Ｇａ_２Ｏ_３系単結晶のａ軸及びｃ軸が紙面に平行であり、ｂ軸が紙面に垂直である。 FIGS. 7A and 7B are conceptual diagrams showing the range of the crystal growth direction of the β-Ga ₂ O ₃ based single crystal according to the _second embodiment. In FIG. 7A, the b-axis and c-axis of the β-Ga ₂ O ₃ single crystal are parallel to the paper surface. In FIG. 7B, the a-axis and c-axis of the β-Ga ₂ O ₃ -based single crystal are parallel to the paper surface, and the b-axis is perpendicular to the paper surface.

本実施の形態のβ−Ｇａ_２Ｏ_３系単結晶の結晶成長方向は、β−Ｇａ_２Ｏ_３系単結晶の（１００）面に垂直な直線３となす角度がθ以内の方向である。すなわち、図７（ａ）、（ｂ）に点線で示される円錐４内を通る方向である。ここで、円錐４は、直線３を軸とした、軸と稜線のなす角度がθの直円錐である。 Crystal growth direction of the β-Ga ₂ O ₃ system single crystal of the present embodiment, the angle formed by the β-Ga ₂ O ₃ system single crystal (100) perpendicular to the plane linear 3 is the direction within theta. That is, it is a direction passing through the inside of the cone 4 indicated by a dotted line in FIGS. Here, the cone 4 is a right cone whose angle between the axis and the ridge line is θ with the straight line 3 as an axis.

角度θは５５．２°であり、より好ましくは３６．２°であり、さらに好ましくは１３．７°であり、最も好ましくは０°である。結晶成長方向が（１００）面に垂直な直線３となす角度が小さいほど、β−Ｇａ_２Ｏ_３系単結晶の成長時の双晶化を効果的に抑えることができる。 The angle θ is 55.2 °, more preferably 36.2 °, even more preferably 13.7 °, and most preferably 0 °. As the angle between the crystal growth direction and the straight line 3 perpendicular to the (100) plane is smaller, twinning during the growth of the β-Ga ₂ O ₃ -based single crystal can be effectively suppressed.

例えば、ＦＺ法によりβ−Ｇａ_２Ｏ_３系単結晶を直線３に平行な方向に成長させた場合、及びａ軸方向、すなわち＜１００＞方向に成長させた場合、成長方向に２５ｃｍ以上にわたって、結晶構造が反転した反転領域が現れないことが確認されている。また、β−Ｇａ_２Ｏ_３系単結晶をｂ軸方向、すなわち＜０１０＞方向に成長させた場合、成長方向と垂直な方向の１ｃｍ当たりの反転領域の平均数が数十以上になることが確認されている。ここで、直線３に平行な方向が直線３となす角度は０°、ａ軸方向が直線３となす角度は１３．７°、ｂ軸方向が直線３となす角度は９０°である。 For example, when a β-Ga ₂ O ₃ single crystal is grown in the direction parallel to the straight line 3 by the FZ method, and when grown in the a-axis direction, that is, in the <100> direction, the growth direction extends over 25 cm or more. It has been confirmed that an inversion region in which the crystal structure is inverted does not appear. Further, when the β-Ga ₂ O ₃ single crystal is grown in the b-axis direction, that is, the <010> direction, the average number of inversion regions per 1 cm in the direction perpendicular to the growth direction may be several tens or more. It has been confirmed. Here, the angle formed between the direction parallel to the straight line 3 and the straight line 3 is 0 °, the angle formed between the a-axis direction and the straight line 3 is 13.7 °, and the angle formed between the b-axis direction and the straight line 3 is 90 °.

なお、第１の実施の形態で述べられた（１０１）面内における＜１０−１＞方向となす角度が０°である方向は、直線３に対して３６．２°の角度をなす。また、（１０１）面内における＜１０−１＞方向となす角度が４５°である方向は、直線３に対して５５．２°の角度をなす。 Note that the direction in which the angle formed with the <10-1> direction in the (101) plane described in the first embodiment is 0 ° forms an angle of 36.2 ° with the straight line 3. Further, the direction in which the angle formed with the <10-1> direction in the (101) plane is 45 ° forms an angle of 55.2 ° with respect to the straight line 3.

β−Ｇａ_２Ｏ_３系単結晶の成長にＦＺ法を用いる場合、ＥＦＧ法を用いる場合と比較して、結晶が双晶化しにくいことが本発明者らにより確認されている。そのため、第１の実施の形態に記載されたＥＦＧ法を用いる場合の結晶成長方向と双晶化度の関係から、ＦＺ法により直線３に対して３６．２°の角度をなす方向に結晶を成長させた場合、結晶が双晶化しないことが予測される。また、ＦＺ法により直線３に対して５５．２°の角度をなす方向に結晶を成長させた場合、成長方向と垂直な方向の１ｃｍ当たりの反転領域の平均数が９本以下になると予測される。 It has been confirmed by the present inventors that when the FZ method is used for the growth of a β-Ga ₂ O ₃ based single crystal, the crystal is less likely to be twinned as compared with the case where the EFG method is used. Therefore, from the relationship between the crystal growth direction and the twinning degree when using the EFG method described in the first embodiment, the crystal is formed in a direction that forms an angle of 36.2 ° with respect to the straight line 3 by the FZ method. When grown, the crystals are expected not to twin. In addition, when a crystal is grown in a direction that forms an angle of 55.2 ° with respect to the straight line 3 by the FZ method, the average number of inversion regions per 1 cm in a direction perpendicular to the growth direction is predicted to be 9 or less. The

（実施の形態の効果）
本実施の形態によれば、β−Ｇａ_２Ｏ_３系単結晶の結晶方位とその成長方向を制御することにより、β−Ｇａ_２Ｏ_３系単結晶の双晶化を効果的に抑えることができる。 (Effect of embodiment)
According to this embodiment, by controlling the crystal orientation and the growth direction of the β-Ga ₂ O ₃ single crystal, it is possible to suppress the twinning of β-Ga ₂ O ₃ single crystal effectively it can.

以上、本発明の実施の形態を説明したが、上記に記載した実施の形態は特許請求の範囲に係る発明を限定するものではない。また、実施の形態の中で説明した特徴の組合せの全てが発明の課題を解決するための手段に必須であるとは限らない点に留意すべきである。 While the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

３…直線、４…円錐、１０…ＥＦＧ結晶製造装置、２５…β−Ｇａ_２Ｏ_３系単結晶、２６…面 3 ... linear, 4 ... cone, 10 ... EFG crystal manufacturing _{_{apparatus, 25 ... β-Ga 2 O}} 3 single crystal, 26 ... surface

Claims

A β-Ga ₂ O ₃ based single crystal is grown in a direction parallel to the (101) plane (excluding directions in a range of plus or minus 10 ° with respect to the b-axis <010> direction) , and the (101) plane The angle φ (0 ° ≦ φ <90 °) between the <10-1> direction and the direction is less than 90 ° ,
A method for growing a β-Ga ₂ O ₃ single crystal.

The angle φ is 45 ° or less.
A method for growing a β-Ga ₂ O ₃ single crystal according to claim 1.

The angle φ is 20 ° or less.
A method for growing a β-Ga ₂ O ₃ single crystal according to claim 2.

The angle φ is 0 °,
A method for growing a β-Ga ₂ O ₃ single crystal according to claim 3.

The β-Ga ₂ O ₃ -based single crystal is a flat crystal having the (101) plane as a main surface.
The method for growing a β-Ga ₂ O ₃ single crystal according to any one of claims 1 to 4.

Growing the β-Ga ₂ O ₃ single crystal by EFG method,
A method for growing a β-Ga ₂ O ₃ single crystal according to claim 5.

The angle between the β-Ga ₂ O ₃ based single crystal and a straight line perpendicular to the (100) plane is within 55.2 ° (the direction is within ± 10 ° with respect to the a-axis <100> direction). Excluding) ,
A method for growing a β-Ga ₂ O ₃ single crystal.

a β-Ga ₂ O ₃ single crystal is grown in a direction of 0 ° with respect to a straight line perpendicular to the (100) plane;
A method for growing a β-Ga ₂ O ₃ single crystal according to claim 7.

Growing the β-Ga ₂ O ₃ based single crystal by FZ method,
The method for growing a β-Ga ₂ O ₃ single crystal according to claim 7 or 8.