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JP4700464B2 - Compound semiconductor device - Google Patents

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JP4700464B2
JP4700464B2 JP2005286495A JP2005286495A JP4700464B2 JP 4700464 B2 JP4700464 B2 JP 4700464B2 JP 2005286495 A JP2005286495 A JP 2005286495A JP 2005286495 A JP2005286495 A JP 2005286495A JP 4700464 B2 JP4700464 B2 JP 4700464B2
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hexagonal
semiconductor layer
crystal
based semiconductor
layer
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JP2007096200A (en
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隆 宇田川
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Resonac Holdings Corp
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Showa Denko KK
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Priority to DE112006002403T priority patent/DE112006002403T5/en
Priority to PCT/JP2006/318098 priority patent/WO2007029865A1/en
Priority to US12/066,055 priority patent/US8084781B2/en
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Description

本発明は、単結晶材料の表面に接合させて設けた燐化硼素系半導体層を備えてなる化合物半導体素子に関する。   The present invention relates to a compound semiconductor element comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material.

従来から、立方晶で閃亜鉛鉱結晶型の燐化硼素系半導体層は、例えば、立方晶の閃亜鉛鉱結晶型の燐化ガリウム(GaP)単結晶や、炭化珪素(SiC)単結晶からなる基板上に形成されている(下記の特許文献1参照)。これらの基板と、その上に形成された燐化硼素系半導体層と、それに接合させて設けたIII族窒化物半導体層とを備えた積層構造体を用いて、例えば、化合物半導体発光ダイオード(LED)が構成されている(下記の特許文献2参照)。
特開平2−288388号公報 特開平2−275682号公報
Conventionally, a cubic zinc blende crystal boron phosphide-based semiconductor layer is made of, for example, a cubic zinc blende crystal gallium phosphide (GaP) single crystal or silicon carbide (SiC) single crystal. It is formed on a substrate (see Patent Document 1 below). Using a stacked structure including these substrates, a boron phosphide-based semiconductor layer formed thereon, and a group III nitride semiconductor layer provided in contact therewith, for example, a compound semiconductor light emitting diode (LED (See Patent Document 2 below).
JP-A-2-288388 JP-A-2-275682

また、珪素単結晶(シリコン)を基板として、その基板上に単量体の燐化硼素(BP)などの閃亜鉛鉱結晶型の立方晶燐化硼素系半導体層が形成されている(下記の特許文献3参照)。また、シリコン基板と、その基板上の単量体のBP層と、そのBP層上に設けたIII族窒化物半導体層とを備えた積層構造体からLEDを構成する技術が開示されている(下記の特許文献3参照)。
米国特許第6069021号
Further, a zinc-blende crystal type cubic boron phosphide-based semiconductor layer such as monomeric boron phosphide (BP) is formed on a silicon single crystal (silicon) as a substrate (described below). (See Patent Document 3). In addition, a technique for forming an LED from a laminated structure including a silicon substrate, a monomeric BP layer on the substrate, and a group III nitride semiconductor layer provided on the BP layer is disclosed ( See Patent Document 3 below).
US Pat. No. 6,690,021

しかしながら、例えば、シリコンを基板として、その(111)結晶面からなる表面上に形成された立方晶の燐化硼素系半導体層には、双晶や積層欠陥などの結晶欠陥が含まれていることが知られている(下記の非特許文献1参照)。また、例えば、六方晶6H型SiCを基板として、その(0.0.0.1.)結晶面上に形成された立方晶の単量体のBP層にも、双晶などの結晶欠陥が含まれていることが報告されている(下記の非特許文献2参照)。この様な結晶欠陥を多量に含む立方晶の燐化硼素系半導体層を備えた積層構造体を利用しても、例えば、逆方向電圧が高く、また、光電変換効率も高いLEDを安定して作製できない問題がある。
T. Udagawa and G. Shimaoka, J. Ceramic Processing and Research,(大韓民国), 第4巻、第2号、2003年,80-83頁. T. Udagawa他、Appl. Surf. Sci.,(アメリカ合衆国),第244巻、2004年,285-288頁.
However, for example, a cubic boron phosphide-based semiconductor layer formed on the surface of the (111) crystal plane using silicon as a substrate contains crystal defects such as twins and stacking faults. Is known (see Non-Patent Document 1 below). Also, for example, a cubic monomer BP layer formed on a (0.0.0.1.) Crystal plane using hexagonal 6H-type SiC as a substrate also has crystal defects such as twins. It is reported that it is contained (see Non-Patent Document 2 below). Even when a stacked structure including a cubic boron phosphide-based semiconductor layer containing a large amount of such crystal defects is used, for example, an LED having a high reverse voltage and a high photoelectric conversion efficiency can be stably produced. There is a problem that cannot be produced.
T. Udagawa and G. Shimaoka, J. Ceramic Processing and Research, (South Korea), Vol. 4, No. 2, 2003, pp. 80-83. T. Udagawa et al., Appl. Surf. Sci., (USA), 244, 2004, pp. 285-288.

本発明は、上記従来技術の問題点を克服すべくなされたもので、燐化硼素系半導体層を双晶や積層欠陥等の結晶欠陥の密度の小さな結晶性に優れたものすることができ、この燐化硼素系半導体層を利用して、素子としての諸特性を向上させることができる化合物半導体素子を提供することを目的とする。   The present invention has been made to overcome the above-mentioned problems of the prior art, and the boron phosphide-based semiconductor layer can have excellent crystallinity with a small density of crystal defects such as twins and stacking faults, An object of the present invention is to provide a compound semiconductor element that can improve various characteristics as an element by using the boron phosphide-based semiconductor layer.

1)上記目的を達成するために、第1の発明は、単結晶材料の表面に接合させて設けた燐化硼素系半導体層を備えてなる化合物半導体素子において、上記単結晶材料は六方晶でその層厚の増加方向に略平行に{0.0.0.1.}結晶面が配列され、上記燐化硼素系半導体層は、{0.0.0.2.}結晶面が上記単結晶材料の表面に略垂直に配列されるとともに、その{0.0.0.2.}結晶面の連続するn個分(nは2以上の正の整数)の距離が、単結晶材料のc軸の長さと略同等となるようにしたものである。   1) To achieve the above object, according to a first aspect of the present invention, there is provided a compound semiconductor device comprising a boron phosphide-based semiconductor layer bonded to the surface of a single crystal material, wherein the single crystal material is hexagonal. Almost parallel to the increasing direction of the layer thickness {0.0.0.1. } The crystal planes are arranged, and the boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer greater than or equal to 2) is set to be approximately equal to the length of the c-axis of the single crystal material.

2)第2の発明は、上記した1)項に記載の発明の構成において、上記{0.0.0.2.}結晶面の個数nを6以下とするものである。   2) A second aspect of the present invention is the above-described {0.0.0.2. } The number n of crystal faces is 6 or less.

本発明によれば、単結晶材料の表面に接合させて設けた燐化硼素系半導体層を備えてなる化合物半導体素子において、単結晶材料は六方晶でその層厚の増加方向に略平行に{0.0.0.1.}結晶面が配列され、燐化硼素系半導体層は、{0.0.0.2.}結晶面が単結晶材料の表面に略垂直に配列されるとともに、その{0.0.0.2.}結晶面の連続するn個分(nは2以上の正の整数)の距離が、単結晶材料のc軸の長さと略同等となるように構成したので、六方晶の燐化硼素系半導体層は、六方晶の単結晶材料との長周期的な整合性に優れるために、結晶欠陥の少ない、結晶性に優れたものとなり、その六方晶の燐化硼素系半導体層を利用する化合物半導体素子の特性を向上させるのに効果を上げられる。   According to the present invention, in a compound semiconductor device comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material, the single crystal material is hexagonal and substantially parallel to the increasing direction of the layer thickness { 0.0.0.1. } The crystal planes are arranged and the boron phosphide-based semiconductor layer is {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } Since the distance of n consecutive crystal planes (n is a positive integer of 2 or more) is substantially equal to the length of the c-axis of the single crystal material, a hexagonal boron phosphide-based semiconductor Since the layer has excellent long-term consistency with a hexagonal single crystal material, it has few crystal defects and excellent crystallinity, and the compound semiconductor uses the hexagonal boron phosphide-based semiconductor layer. This is effective for improving the characteristics of the element.

また、本発明によれば、燐化硼素系半導体層の{0.0.0.2.}結晶面の個数nを6以下としたので、ミスフィット(misfit)転位の少ない良質の六方晶の燐化硼素系半導体層を得ることができ、それによって、例えば電気的耐圧性に優れるLEDをもたらすのに効果を上げられる。   Further, according to the present invention, the boron phosphide-based semiconductor layer {0.0.0.2. } Since the number n of crystal planes is 6 or less, a high-quality hexagonal boron phosphide-based semiconductor layer with few misfit dislocations can be obtained. It is effective to bring.

本発明は、単結晶材料の表面に接合させて設けた燐化硼素系半導体層を備えてなる化合物半導体素子において、単結晶材料は六方晶でその層厚の増加方向に略平行に{0.0.0.1.}結晶面が配列され、燐化硼素系半導体層は、{0.0.0.2.}結晶面が単結晶材料の表面に略垂直に配列されるとともに、その{0.0.0.2.}結晶面の連続するn個分(nは2以上の正の整数)の距離が、単結晶材料のc軸の長さ({0.0.0.1.}結晶面の間隔)と略同等となるようにしている。   The present invention relates to a compound semiconductor device comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material, the single crystal material being hexagonal and substantially parallel to the increasing direction of the layer thickness {0. 0.0.1. } The crystal planes are arranged and the boron phosphide-based semiconductor layer is {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately the length of the c-axis of the single crystal material (interval of {0.0.0.1.} Crystal planes). It is trying to be equivalent.

本発明に係る六方晶の燐化硼素系半導体層とは、硼素(元素記号:B)と燐(元素記号:P)とを必須の構成元素として含む六方晶の結晶層である。例えば、六方晶の単量体の燐化硼素(BP)であり、硼素(B)とそれとは別のIII族元素を構成元素として含む、例えば六方晶の燐化硼素アルミニウム混晶(組成式B1-XAlXP:0<X<1)、燐化硼素ガリウム混晶(組成式B1-XGaXP:0<X<1)や燐化硼素インジウム混晶(組成式B1-XInXP:0<X<1)である。硼素(B)とそれとは別のIII族元素を構成元素として含む混晶にあって、硼素(B)とは別のIII族元素の好ましい組成比(上記の組成式におけるX)は、0.40以下である。その組成比(=X)が0.40を超えると六方晶ではなく立方晶の燐化硼素系半導体層が急激に形成され易くなるからである。 The hexagonal boron phosphide-based semiconductor layer according to the present invention is a hexagonal crystal layer containing boron (element symbol: B) and phosphorus (element symbol: P) as essential constituent elements. For example, hexagonal monomer boron phosphide (BP), which contains boron (B) and another group III element as a constituent element, for example, hexagonal boron phosphide aluminum mixed crystal (composition formula B 1-X Al X P: 0 <X <1), boron gallium phosphide mixed crystal (composition formula B 1-X Ga X P: 0 <X <1) and boron phosphide indium mixed crystal (composition formula B 1- X In X P: 0 <X <1). In a mixed crystal containing boron (B) and another group III element as a constituent element, a preferred composition ratio of the group III element different from boron (B) (X in the above composition formula) is 0. 40 or less. This is because when the composition ratio (= X) exceeds 0.40, a cubic boron phosphide-based semiconductor layer rather than a hexagonal crystal is easily formed.

また、本発明に係る六方晶の燐化硼素系半導体層として、燐(P)と燐(P)とは別のV族元素を含む、例えば、六方晶の燐化砒化硼素(組成式BP1-YAsY:0<Y<1)や窒化燐化硼素(組成式BNY1-Y:0<Y<1)を例示できる。結晶成長の簡易さ、組成制御の煩雑さなどを勘案すると、六方晶の燐化硼素系半導体層は単量体の燐化硼素(BP)から構成するのが好適である。 Further, the hexagonal boron phosphide-based semiconductor layer according to the present invention contains, for example, a hexagonal boron arsenide phosphide (composition formula BP 1 ) containing a group V element different from phosphorus (P) and phosphorus (P). -Y As Y : 0 <Y <1) and boron nitride phosphide (compositional formula BN Y P 1-Y : 0 <Y <1). Taking into account the simplicity of crystal growth and the complexity of composition control, the hexagonal boron phosphide-based semiconductor layer is preferably composed of monomeric boron phosphide (BP).

本発明に係る六方晶の燐化硼素系半導体層と接合をなす六方晶の単結晶材料としては、サファイア(α―Al23単結晶)、ウルツ鉱結晶型のGaN等のIII族窒化物半導体、酸化亜鉛(ZnO)、Ramsdellの表記によるところの2H型(ウルツ鉱結晶型)または4H型或いは6H型の炭化珪素(SiC)等のバルク(bulk)単結晶或いは単結晶層を例示できる。 Examples of the hexagonal single crystal material bonded to the hexagonal boron phosphide-based semiconductor layer according to the present invention include group III nitrides such as sapphire (α-Al 2 O 3 single crystal) and wurtzite crystal type GaN. Examples include semiconductors, zinc oxide (ZnO), bulk single crystals or single crystal layers such as 2H type (wurtzite crystal type) or 4H type or 6H type silicon carbide (SiC) in terms of Ramsdell.

本発明では、これらのバルク単結晶或いは単結晶層からなる六方晶の単結晶材料にあって、特に、その層厚の増加方向(成長方向)に略平行に{0.0.0.1.}結晶面が配列されている六方晶の単結晶材料を用いる。したがって、この単結晶材料の表面は、例えば{1.0.−1.0.}結晶面や{1.1.−2.0.}結晶面となる。なお、ここで層厚の増加方向とは、各層の積層方向であり、以下の説明では垂直方向と表現する場合もある。また、単結晶材料の層厚の増加方向に略平行に{0.0.0.1.}結晶面が配列されているが、この略平行とは、垂直方向に対して好ましくは±10度の範囲にあるものをいう。この範囲から外れると、その上に積層する層に双晶や結晶欠陥が多く発生するようになる。   In the present invention, there is a hexagonal single crystal material composed of these bulk single crystals or single crystal layers, and in particular, substantially in parallel with the increasing direction (growth direction) of the layer thickness {0.0.0.1. } Use a hexagonal single crystal material with crystal planes arranged. Therefore, the surface of this single crystal material is, for example, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } It becomes a crystal plane. Here, the increasing direction of the layer thickness is the stacking direction of the layers, and may be expressed as a vertical direction in the following description. Further, substantially in parallel with the increasing direction of the layer thickness of the single crystal material {0.0.0.1. } Although crystal planes are arranged, the term “substantially parallel” means that the crystal plane is preferably within a range of ± 10 degrees with respect to the vertical direction. If it is out of this range, many twins and crystal defects are generated in the layer laminated thereon.

上記のように、本発明では、単結晶材料の{1.0.−1.0.}結晶面や{1.1.−2.0.}結晶面からなる表面に、六方晶の燐化硼素系半導体層を設けるようにしている。例えば、2H型、4H型、或いは6H型の六方晶の炭化珪素単結晶からなる単結晶材料の、{1.0.−1.0.}結晶面や{1.1.−2.0.}結晶面からなる表面に六方晶の燐化硼素系半導体層を設ける。また、ウルツ鉱結晶型の六方晶の窒化アルミニウム(AlN)や、同じくウルツ鉱結晶型の六方晶のGaNからなる単結晶材料の、{1.0.−1.0.}結晶面や{1.1.−2.0.}結晶面からなる表面に六方晶の燐化硼素系半導体層を設ける。また、サファイア(α−アルミナ単結晶)からなる単結晶材料の、{1.0.−1.0.}結晶面(通称、M面またはm面)や{1.1.−2.0.}結晶面(通称、A面またはa面)からなる表面に、六方晶の燐化硼素系半導体層を設けるのが好適である。   As described above, in the present invention, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the crystal plane. For example, a single crystal material made of a hexagonal silicon carbide single crystal of 2H type, 4H type, or 6H type {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the surface of the crystal plane. Further, a single crystal material made of wurtzite crystal type hexagonal aluminum nitride (AlN) or a wurtzite crystal type hexagonal GaN, {1.0. -1.0. } Crystal plane or {1.1. -2.0. } A hexagonal boron phosphide-based semiconductor layer is provided on the surface of the crystal plane. Further, a single crystal material made of sapphire (α-alumina single crystal), {1.0. -1.0. } Crystal plane (common name, M plane or m plane) and {1.1. -2.0. } It is preferable to provide a hexagonal boron phosphide-based semiconductor layer on the surface composed of a crystal plane (commonly referred to as A-plane or a-plane).

そして、六方晶の燐化硼素系半導体層は、詳細は後述するように、{0.0.0.2.}結晶面が単結晶材料の表面に略垂直に配列されるとともに、その{0.0.0.2.}結晶面の連続するn個分(nは2以上の正の整数)の距離が、単結晶材料のc軸の長さ({0.0.0.1.}結晶面の間隔)と略同等となるようにしている。すなわち、燐化硼素系半導体層の{0.0.0.2.}結晶面の連続するn個分の距離と、単結晶材料のc軸の長さとを長周期的にマッチングさせている。なお、上記のように、六方晶の燐化硼素系半導体層には{0.0.0.2.}結晶面が単結晶材料の表面に略垂直に配列されるが、この略垂直とは、垂直方向に対して好ましくは±10度の範囲にあるものをいう。この範囲から外れると、その上に積層する層に双晶や結晶欠陥が多く発生するようになる。   The hexagonal boron phosphide-based semiconductor layer has a {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0.0.2. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately the length of the c-axis of the single crystal material (interval of {0.0.0.1.} Crystal planes). It is trying to be equivalent. That is, the boron phosphide-based semiconductor layer {0.0.0.2. } The distance of n consecutive crystal planes and the length of the c-axis of the single crystal material are matched periodically. As described above, the hexagonal boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal planes are arranged substantially perpendicular to the surface of the single crystal material, and the term “substantially perpendicular” means that the crystal plane is preferably within a range of ± 10 degrees with respect to the vertical direction. If it is out of this range, many twins and crystal defects are generated in the layer laminated thereon.

六方晶の燐化硼素系半導体層は、上記の様な好適な結晶面からなる表面上に、ハロゲン(halogen)法、ハイドライド(hydride)法、有機金属化学堆積(英略称:MOCVD)法等の気相成長手段により形成できる。例えば、トリエチル硼素(分子式(C253B)を硼素(B)源とし、トリエチル燐(分子式(C253P)を燐(P)源とするMOCVD法により形成できる。また、三塩化硼素(分子式BCl3)を硼素源とし、三塩化燐(分子式PCl3)を燐源とするハロゲンCVD法により形成できる。また、ガスソース(gas source)分子線エピタキシャル(英略称:GS−MBE)法やケミカルビームエピタキシャル(英略称:CBE)法などの真空環境下で成膜する成長手段により形成できる。 A hexagonal boron phosphide-based semiconductor layer is formed on a surface having a suitable crystal plane as described above, such as a halogen method, a hydride method, or a metal organic chemical deposition (abbreviation: MOCVD) method. It can be formed by vapor phase growth means. For example, it can be formed by MOCVD using triethyl boron (molecular formula (C 2 H 5 ) 3 B) as a boron (B) source and triethyl phosphorus (molecular formula (C 2 H 5 ) 3 P) as a phosphorus (P) source. Further, it can be formed by a halogen CVD method using boron trichloride (molecular formula BCl 3 ) as a boron source and phosphorus trichloride (molecular formula PCl 3 ) as a phosphorus source. Alternatively, the film can be formed by a growth means for forming a film in a vacuum environment such as a gas source molecular beam epitaxial (abbreviation: GS-MBE) method or a chemical beam epitaxial (abbreviation: CBE) method.

六方晶の単結晶材料の上記の好適な結晶面からなる表面上に、例えば、常圧(略大気圧)或いは減圧MOCVD法により、六方晶の燐化硼素系半導体層を形成するのに際し、(a)成長させる温度は750℃以上で850℃以下とし、且つ、(b)成長反応系へ供給する硼素(B)源に対する燐(P)源の濃度比率(所謂、V/III比率)を、400以上500以下の範囲とし、尚且つ、(C)燐化硼素系半導体層の成長速度を毎分20nm以上で毎分30nm以下とすると、層厚の増加方向(上記の単結晶材料の表面に対して垂直方向)に平行に、等間隔で規則的に{0002}結晶面を配列してなる六方晶の燐化硼素系半導体層を形成することができる。   When a hexagonal boron phosphide-based semiconductor layer is formed on the surface of the above-mentioned preferred crystal plane of the hexagonal single crystal material by, for example, atmospheric pressure (substantially atmospheric pressure) or low pressure MOCVD method, a) The growth temperature is 750 ° C. or more and 850 ° C. or less, and (b) the concentration ratio (so-called V / III ratio) of the phosphorus (P) source to the boron (B) source supplied to the growth reaction system, When the growth rate of the boron phosphide-based semiconductor layer (C) is 20 nm / min or more and 30 nm / min or less in the range of 400 or more and 500 or less, the increase direction of the layer thickness (on the surface of the single crystal material described above) On the other hand, a hexagonal boron phosphide-based semiconductor layer in which {0002} crystal planes are regularly arranged at regular intervals in parallel to the vertical direction) can be formed.

六方晶の燐化硼素系半導体層の成長速度は、成長反応系へ単位時間あたりに供給する硼素(B)等のIII族構成元素源の濃度を増加させれば、上記の成長温度範囲では、その濃度に略比例して増加させられる。また、成長反応系に単位時間あたりに供給する硼素等のIII族構成元素源の濃度を一定とした場合、成長温度を高温とする程、成長速度は増加させられる。750℃未満の低温では、そもそも、硼素(B)源や燐(P)源の熱分解が充分に起こらないため、成長速度は急激に低下し、上記の好適な成長速度を得るに至らない。一方、成長温度を850℃を越える高温とするのは、組成式B6P等の多量体の燐化硼素結晶が急激に発生することもあり、好ましくない。 The growth rate of the hexagonal boron phosphide-based semiconductor layer is such that if the concentration of a group III constituent element source such as boron (B) supplied per unit time to the growth reaction system is increased, It is increased in proportion to the concentration. Further, when the concentration of a group III constituent element such as boron supplied to the growth reaction system per unit time is constant, the growth rate is increased as the growth temperature is increased. At a low temperature of less than 750 ° C., the thermal decomposition of the boron (B) source and the phosphorus (P) source does not occur sufficiently in the first place, so that the growth rate decreases rapidly and the above-mentioned preferable growth rate cannot be obtained. On the other hand, a growth temperature exceeding 850 ° C. is not preferable because a multimeric boron phosphide crystal such as a composition formula B 6 P may be rapidly generated.

例えば、ホスフィン(分子式PH3)を燐源とし、トリエチル硼素((C253B)を硼素源とするMOCVD法により、六方晶のBP層を形成する場合、成長温度を800℃とし、成長反応系に供給する原料の濃度比率、即ち、PH3/(C253B比率を450とし、尚且つ、成長速度を毎分25nmとして形成する。 For example, when a hexagonal BP layer is formed by MOCVD using phosphine (molecular formula PH 3 ) as a phosphorus source and triethyl boron ((C 2 H 5 ) 3 B) as a boron source, the growth temperature is set to 800 ° C. The concentration ratio of the raw material supplied to the growth reaction system, that is, the PH 3 / (C 2 H 5 ) 3 B ratio is set to 450, and the growth rate is set to 25 nm per minute.

六方晶の単結晶材料の上記の好適な結晶面からなる表面上に、その表面に対して垂直方向に平行に配列した{0.0.0.2.}結晶面からなる六方晶の燐化硼素系半導体層を安定して形成するには、その表面に吸着している余計な物質を脱着したる後、燐化硼素系半導体層の成長を開始するのが好ましい。例えば、六方晶の単結晶材料を、真空中で、六方晶の燐化硼素系半導体層を成長させるのに好ましい温度を超える温度に加熱して、例えば、850℃を超える温度に加熱して、六方晶の単結晶材料の表面に吸着している分子を脱着させた後、燐化硼素系半導体層を成長させるのが好ましい。六方晶の燐化硼素系半導体層は、吸着分子を脱着させ、清浄化した六方晶の単結晶材料の表面の状態を保持したままで、その清浄表面に成長させるのが好ましい。この観点からして、六方晶の燐化硼素半導体層を成長させる手段は、高真空環境下で成長を行うMBE法やCBE法が適する。また、減圧された環境下で成長行う減圧化学的気相堆積(CVD)法が適する。   The hexagonal single crystal material was arranged on the surface composed of the above-mentioned preferred crystal planes in parallel to the surface in a direction perpendicular to the surface {0.0.0.2. } To stably form a hexagonal boron phosphide-based semiconductor layer consisting of crystal planes, after desorbing excess material adsorbed on the surface, growth of the boron phosphide-based semiconductor layer is started. Is preferred. For example, a hexagonal single crystal material is heated in vacuum to a temperature above a preferred temperature for growing a hexagonal boron phosphide-based semiconductor layer, for example, to a temperature above 850 ° C., It is preferable to grow the boron phosphide-based semiconductor layer after desorbing molecules adsorbed on the surface of the hexagonal single crystal material. The hexagonal boron phosphide-based semiconductor layer is preferably grown on the cleaned surface while desorbing adsorbed molecules and maintaining the surface state of the cleaned hexagonal single crystal material. From this point of view, an MBE method or a CBE method for growing in a high vacuum environment is suitable as a means for growing a hexagonal boron phosphide semiconductor layer. Further, a low pressure chemical vapor deposition (CVD) method in which growth is performed in a reduced pressure environment is suitable.

上記の様な好適な結晶面からなる清浄化された、六方晶の単結晶材料の表面上には、上記したように、六方晶の単結晶材料のc軸の長さに関し、長周期的にマッチングする六方晶の燐化硼素系半導体層を安定して形成できる。図1に本発明の云う六方晶の燐化硼素系半導体層に係る長周期的マッチングの様子を模式的に示す。同図には、六方晶の単結晶材料11を{1.0.−1.0.}結晶面を表面11Aとするサファイアとし、その表面11Aに接合させて設ける六方晶の燐化硼素系半導体層12をB0.98Al0.02P層とした場合の長周期マッチングの模様を例示してある。同図に示す如く、{1.0.−1.0.}結晶面を表面11Aとするサファイアの内部では、{0.0.0.1.}結晶面11Bが表面11Aに垂直に、且つ、互いに平行に規則的に配列している。また、接合面12Aをもって六方晶の単結晶材料の表面11Aに接合した六方晶の燐化硼素系半導体層12の内部では、サファイアの{0.0.0.1.}結晶面11Bに平行に、{0.0.0.2.}結晶面12Bが合計6面配列している。すなわち、単結晶材料11と燐化硼素系半導体層12との接合系10にあって、清浄化されたサファイアの表面11Aには、図1に示すように、サファイアのc軸の長さ(1.30nm)に等しい間隔(図1中の“c軸の長さ”)において、合計6面の{0.0.0.2.}結晶面12Bが配置している。 As described above, on the surface of the cleaned hexagonal single crystal material having a suitable crystal plane as described above, the length of the c-axis of the hexagonal single crystal material is long-period. A matching hexagonal boron phosphide-based semiconductor layer can be formed stably. FIG. 1 schematically shows long-period matching according to the hexagonal boron phosphide-based semiconductor layer of the present invention. In the figure, a hexagonal single crystal material 11 is represented by {1.0. -1.0. } An example of a long-period matching pattern in the case where sapphire having a crystal surface of 11A and a hexagonal boron phosphide-based semiconductor layer 12 bonded to the surface 11A is a B 0.98 Al 0.02 P layer is illustrated. . As shown in FIG. -1.0. } Inside the sapphire whose crystal plane is the surface 11A, {0.0.0.1. The crystal planes 11B are regularly arranged perpendicular to the surface 11A and parallel to each other. In addition, in the hexagonal boron phosphide-based semiconductor layer 12 bonded to the surface 11A of the hexagonal single crystal material with the bonding surface 12A, {0.0.0.1. } Parallel to the crystal plane 11B, {0.0.0.2. } There are a total of six crystal faces 12B arranged. That is, in the bonding system 10 of the single crystal material 11 and the boron phosphide-based semiconductor layer 12, the surface 11A of the cleaned sapphire has a c-axis length (1 of sapphire as shown in FIG. .30 nm) (“c-axis length” in FIG. 1), a total of six {0.0.0.2. } The crystal face 12B is arranged.

換言すれば、六方晶の単結晶材料11上には、そのc軸の長さと、n(nは2以上の正の整数、例えば2,3,4,5または6)個の{0.0.0.2.}結晶面12Bの互いの間隔dの合計の長さ(=(n−1)×d)とを等しくして、即ち、長周期的にマッチングした状態で、六方晶の燐化硼素系半導体層が形成され得る。dは、隣接する2つの{0.0.0.2.}結晶面の間隔をもって与えられることから、{0.0.0.2.}結晶面は最低でも2面を必要とする。即ち、nは2以上である。   In other words, on the hexagonal single crystal material 11, the length of the c-axis and n (n is a positive integer of 2 or more, for example, 2, 3, 4, 5 or 6) {0.0 0.2. } A hexagonal boron phosphide-based semiconductor layer in which the total length (= (n−1) × d) of the distance d between the crystal planes 12B is equal, that is, in a state of long-period matching Can be formed. d is two adjacent {0.0.0.2. } Since it is given with an interval of crystal planes, {0.0.0.2. } The crystal face needs at least two faces. That is, n is 2 or more.

サファイアの{1.0.−1.0.}結晶面からなる表面上に接合させて設けたB0.98Al0.02P混晶層やB0.99Ga0.01P混晶にあっては、上記の如く、長周期マッチング構造をなす{0.0.0.2.}結晶面の面数は6、即ち、nは6であるが、GaNの{1.0.−1.0.}結晶面からなる表面上に接合させて設けたBP層にあっては、nは2である。また、AlNの{1.0.−1.0.}結晶面からなる表面上に接合させて設けたBP層にあっても、nは2である。また、GaN或いはAlNからなる単結晶材料の{1.1.−2.0.}結晶面に接合させて設けたBP層にあっても、nは2である。 Sapphire {1.0. -1.0. } A B 0.98 Al 0.02 P mixed crystal layer or a B 0.99 Ga 0.01 P mixed crystal layer bonded to a crystal surface has a long-period matching structure as described above {0.0. .2. } The number of crystal faces is 6, that is, n is 6, but {1.0. -1.0. } N is 2 in the case of a BP layer bonded to the surface of the crystal plane. Also, AlN {1.0. -1.0. } N is 2 even in the BP layer bonded to the surface of the crystal plane. Further, a single crystal material made of GaN or AlN {1.1. -2.0. } N is 2 even in the BP layer bonded to the crystal plane.

六方晶の燐化硼素系半導体層を設ける六方晶の単結晶材料の表面の清浄化が充分に果たされていないと、例えば、表面に残存する酸素(元素記号:O)や水(分子式H2O)等の吸着分子の悪影響に因り、{0.0.0.2.}結晶面が図1に例示した如く、整然と配列した六方晶の燐化硼素系半導体層を充分に安定して得るのに支障を来たす。六方晶の燐化硼素系半導体層を成長させるための原料の分子ではない一酸化炭素(分子式CO)、二酸化炭素(分子式CO2)や窒素(分子式N2)等の余計な分子が六方晶の単結晶材料の表面に残存して吸着している場合も同様に、上記した長周期のマッチング構造を有する六方晶の燐化硼素系半導体層を充分に安定して得ることが出来ず、不都合である。 If the surface of the hexagonal single crystal material provided with the hexagonal boron phosphide-based semiconductor layer is not sufficiently cleaned, for example, oxygen (element symbol: O) remaining on the surface or water (molecular formula H {0.0.0.2. Due to adverse effects of adsorbed molecules such as 2 O). } As shown in FIG. 1, the hexagonal boron phosphide-based semiconductor layer whose crystal planes are regularly arranged is hindered from being obtained sufficiently stably. Extra molecules such as carbon monoxide (molecular formula CO), carbon dioxide (molecular formula CO 2 ) and nitrogen (molecular formula N 2 ), which are not raw material molecules for growing a hexagonal boron phosphide-based semiconductor layer, are hexagonal crystals. Similarly, even when the surface remains adsorbed on the surface of the single crystal material, the hexagonal boron phosphide-based semiconductor layer having the long-period matching structure described above cannot be obtained sufficiently stably. is there.

上記した長周期マッチングを果たす六方晶の燐化硼素系半導体層を安定して得る上での不都合は、吸着した余計な分子に因り、六方晶の燐化硼素系半導体層をなす{0.0.0.2.}結晶面の整然とした規則的な配列が乱されることに起因している。また別の原因として、吸着分子を起点として{0.0.0.2.}結晶面とは異なる面指数の結晶面が形成されてしまうことがある。また他の原因として、吸着分子が残存している領域上には、六方晶の燐化硼素系半導体結晶が成長しないことが挙げられる。従って、長周期のマッチング構造を有する六方晶の燐化硼素系半導体層を接合させて設けるのに際し、六方晶の単結晶材料の表面を清浄する処理は重要である。   The inconvenience in stably obtaining the hexagonal boron phosphide-based semiconductor layer that fulfills the above-mentioned long-period matching is that the hexagonal boron phosphide-based semiconductor layer is formed by the adsorbed extra molecules {0.0 0.2. } This is because the orderly and regular arrangement of crystal planes is disturbed. As another cause, {0.0.0.2. } A crystal face having a plane index different from the crystal face may be formed. Another cause is that the hexagonal boron phosphide-based semiconductor crystal does not grow on the region where the adsorbed molecules remain. Therefore, when the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure is bonded and provided, a treatment for cleaning the surface of the hexagonal single crystal material is important.

真空環境下で成膜するMBE法やCBE法にあっては、六方晶の単結晶材料の表面の吸着分子の存在は、例えば、高速反射電子回折(英略称:RHEED)パターンから察知できる。その表面に吸着している分子が残存する場合、RHEED像は、六方晶の単結晶材料の表面からの元来、帰結されるべきスポット(spot)状或いはストリーク(光条)状ではなく、リング(環)状またはハロー(halo)パターンとなる。また、六方晶の単結晶材料の表面に吸着している分子種は、例えば赤外吸収分光法や紫外吸収分光法等の分析手段により同定出来る。   In the MBE method or the CBE method for forming a film in a vacuum environment, the presence of adsorbed molecules on the surface of a hexagonal single crystal material can be detected from, for example, a high-speed reflection electron diffraction (abbreviation: RHEED) pattern. When molecules adsorbed on the surface remain, the RHEED image is not a spot or streak (light stripe) shape that should originally result from the surface of a hexagonal single crystal material, but a ring. It becomes a (ring) shape or a halo pattern. The molecular species adsorbed on the surface of the hexagonal single crystal material can be identified by an analysis means such as infrared absorption spectroscopy or ultraviolet absorption spectroscopy.

更に、六方晶の単結晶材料の表面に、六方晶の燐化硼素系半導体層を接合させて設けるのに際し、成長速度を毎分20nm未満として、または、毎分30nmを超えて大きくして成長させると、何れの場合も、長周期的にマッチングする六方晶の燐化硼素系半導体層を充分に安定して得るのに支障を来たす。成長速度を毎分20nm未満の低速度とすると、例えば、{0.0.0.2.}結晶面を構成する燐(P)原子が揮散し、長周期マッチング構造をもたらすのに足る{0.0.0.2.}結晶面の数的欠落を生ずるからでる。また、成長速度が毎分30nmを超える高速度の場合、逆に、長周期マッチング構造をもたらすのに足る{0.0.0.2.}結晶面の面数(即ち、本発明のnである。)を超えて、{0.0.0.2.}結晶面が形成されてしまうからである。   Further, when the hexagonal boron phosphide-based semiconductor layer is bonded to the surface of the hexagonal single crystal material, the growth rate is set to less than 20 nm per minute or increased to exceed 30 nm per minute. In either case, it will hinder the stable and stable acquisition of a hexagonal boron phosphide-based semiconductor layer that matches periodically. If the growth rate is a low rate of less than 20 nm per minute, for example, {0.0.0.2. } Phosphorus (P) atoms constituting the crystal plane are volatilized and a long-period matching structure is sufficient {0.0.0.2. } This is because there is a numerical loss of crystal planes. On the other hand, when the growth rate is higher than 30 nm per minute, it is sufficient to provide a long-period matching structure {0.0.0.2. } Beyond the number of crystal faces (that is, n in the present invention), {0.0.0.2. } This is because a crystal plane is formed.

六方晶の単結晶材料の表面のc軸の長さに相当する距離において、長周期的マッチングをなす様に配列している六方晶の燐化硼素系半導体層の{0.0.0.2.}結晶面の面数、即ち、本発明のnは、例えば、透過型電子顕微鏡(英略称:TEM)を利用した電子回折分析或いは断面TEM技法による格子像から調査できる。本発明に係る長周期マッチング構造が形成されている場合、電子回折像上において、六方晶の単結晶材料の{0.0.0.1}結晶面からの回折スポットは、六方晶の燐化硼素系半導体層の{0.0.0.2.}結晶面からの回折スポットの(n−1)倍(合計n個の{0.0.0.2.}結晶面の間の間隔の合計)に等しい間隔をもって出現する。   The hexagonal boron phosphide-based semiconductor layers {0.0.0.2] arranged so as to form long-period matching at a distance corresponding to the length of the c-axis of the surface of the hexagonal single crystal material. . } The number of crystal planes, that is, n in the present invention can be examined from, for example, a lattice image obtained by electron diffraction analysis using a transmission electron microscope (abbreviation: TEM) or a cross-sectional TEM technique. When the long-period matching structure according to the present invention is formed, the diffraction spot from the {0.0.0.1} crystal plane of the hexagonal single crystal material on the electron diffraction image is a hexagonal phosphide. The boron-based semiconductor layer {0.0.0.2. } Appears with an interval equal to (n−1) times the diffraction spot from the crystal plane (the total of the intervals between n {0.0.0.2.} Crystal planes in total).

特に、nを8以下、更に好ましくは6以下とする長周期マッチング構造とするとミスフィット(misfit)転位の少ない結晶性に優れる六方晶の燐化硼素系半導体層を得ることが出来る。六方晶の燐化硼素系半導体層と六方晶の単結晶材料との接合界面近傍の領域で発生する、六方晶の単結晶材料のc軸に垂直な方向の、六方晶の燐化硼素系半導体層の内部のミスミット転位の密度は、上記したnの値に比例して増加する。本発明者による結果によれば、nが6以下の長周期マッチング構造であれば、局所的な電気的耐圧不良を発生するに至らない、ミスフィット転位の密度の小さな良質な六方晶の燐化硼素系半導体層がもたらされることが判っている。   In particular, when a long-period matching structure in which n is 8 or less, more preferably 6 or less, a hexagonal boron phosphide-based semiconductor layer excellent in crystallinity with few misfit dislocations can be obtained. Hexagonal boron phosphide-based semiconductor in the direction perpendicular to the c-axis of the hexagonal single-crystal material generated in the vicinity of the junction interface between the hexagonal boron phosphide-based semiconductor layer and the hexagonal single-crystal material The density of mismit dislocations inside the layer increases in proportion to the value of n described above. According to the results of the present inventors, a long-period matching structure in which n is 6 or less does not lead to local electrical breakdown, and high-quality hexagonal phosphide with a low density of misfit dislocations. It has been found that a boron based semiconductor layer is provided.

nを2以上で6以下とする長周期マッチング構造の六方晶の燐化硼素系半導体層は、ミスフィット転位の密度が小さいために、その結晶性の良好さから良質な成長層を形成するための下地として有効に利用できる。長周期マッチング構造の六方晶の燐化硼素系半導体層上に設けるのに好適なのは、例えば、SiC、酸化亜鉛(ZnO)、GaN、AlN、窒化インジウム(InN)、及びこれらの混晶である窒化アルミニウム・ガリウム・インジウム(組成式AlXGaYInZN:0≦X,Y,Z≦1、X+Y+Z=1)などのIII族窒化物半導体からなる成長層である。また、III族窒化物半導体層としては、他に、窒素(元素記号:N)と窒素以外の燐(元素記号:P)や砒素(元素記号:As)等の第V族元素を含む、例えば、窒化燐化ガリウム(組成式GaN1-YY:0≦Y<1)や窒化砒化ガリウム(組成式GaN1-YAsY:0≦Y<1)からなる成長層を例示できる。 Since the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure in which n is 2 or more and 6 or less has a low misfit dislocation density, a high-quality growth layer is formed because of its good crystallinity. It can be used effectively as a foundation for For example, SiC, zinc oxide (ZnO), GaN, AlN, indium nitride (InN), and a nitride of these mixed crystals are preferably provided on the hexagonal boron phosphide-based semiconductor layer having a long-period matching structure. It is a growth layer made of a group III nitride semiconductor such as aluminum, gallium, and indium (compositional formula Al x Ga y In z N: 0 ≦ X, Y, Z ≦ 1, X + Y + Z = 1). In addition, the group III nitride semiconductor layer includes other group V elements such as nitrogen (element symbol: N) and phosphorus other than nitrogen (element symbol: P) and arsenic (element symbol: As). Examples thereof include growth layers made of gallium nitride phosphide (compositional formula GaN 1-Y P Y : 0 ≦ Y <1) and gallium arsenide nitride (compositional formula GaN 1-Y As Y : 0 ≦ Y <1).

長周期マッチング構造を有する、ミスフィット転位の少ない六方晶の燐化硼素系半導体層を下地として形成した、双晶や転位等の結晶欠陥密度の小さな結晶性に優れる上記の様なIII族窒化物半導体層を利用すれば、高い強度の発光をもたらすpn接合型ヘテロ構造を構成できる。例えば、AlXGaYN(0≦X,Y≦1、X+Y=1)層をクラッド(clad)層とし、GaXIn1-XN(0<X<1)層を発光層とするLED等の発光素子用途のダブルヘテロ(DH)接合型発光部を構成できる。 A III-nitride as described above, which has a long-period matching structure and is formed from a hexagonal boron phosphide-based semiconductor layer with few misfit dislocations as a base and has low crystal defect density such as twins and dislocations. If a semiconductor layer is used, a pn junction type heterostructure that provides high intensity light emission can be formed. For example, an LED having an Al X Ga Y N (0 ≦ X, Y ≦ 1, X + Y = 1) layer as a clad layer and a Ga X In 1-X N (0 <X <1) layer as a light emitting layer. The double hetero (DH) junction type light emission part for light emitting element use etc. can be comprised.

また、化合物半導体発光素子に限らず、結晶欠陥密度が低減された、結晶性に優れるIII族窒化物半導体層を、電子走行層(チャネル層)として利用すれば、ショットキー(Schottky)接触型MESFETを構成できる。チャネル(channel)層は、例えば、不純物を故意に添加していないアンドープ(undope)で高純度なn形GaN層から構成できる。結晶欠陥密度が低減されたIII族窒化物半導体層では、高い電子移動度が顕現されるため、高周波特性に優れるMESFETを得るのに好都合となる。   Further, not only a compound semiconductor light emitting device but also a Group III nitride semiconductor layer with reduced crystal defect density and excellent crystallinity is used as an electron transit layer (channel layer), a Schottky contact MESFET. Can be configured. The channel layer can be composed of, for example, an undoped high-purity n-type GaN layer to which impurities are not intentionally added. In a group III nitride semiconductor layer with a reduced crystal defect density, high electron mobility is manifested, which is advantageous for obtaining a MESFET having excellent high-frequency characteristics.

(実施例) 六方晶の単結晶材料としてサファイアのバルク結晶を用い、その表面上に設けた六方晶の単量体のBP層を利用してLEDを構成する場合を例にして本発明の内容を具体的に説明する。   (Example) Contents of the present invention, taking as an example a case where an LED is constructed using a hexagonal monomer BP layer formed on a surface of a sapphire bulk crystal as a hexagonal single crystal material. Will be described in detail.

図2に本実施例に係るLED20の平面構成を模式的に示す。また、図3には、図2に示した破線A−A‘に沿ったLED20の断面模式図を示す。   FIG. 2 schematically shows a planar configuration of the LED 20 according to the present embodiment. FIG. 3 shows a schematic cross-sectional view of the LED 20 along the broken line A-A ′ shown in FIG. 2.

LED20を作製するための積層構造体200は、(1.1.−2.0.)結晶面(通称A面)を表面とするサファイア(α−アルミナ単結晶)を基板201として形成した。基板201の表面上に六方晶の燐化硼素系半導体層202を形成するのに先立ち、サファイア基板201を一般的な減圧MOCVD装置内で、約0.01気圧の真空下で1200℃に加熱し、その基板201の表面の吸着物質を脱着させ、表面を清浄とした。   The laminated structure 200 for manufacturing the LED 20 was formed using sapphire (α-alumina single crystal) having a (1.1.-2.0.) Crystal plane (commonly referred to as A plane) as the substrate 201. Prior to forming the hexagonal boron phosphide-based semiconductor layer 202 on the surface of the substrate 201, the sapphire substrate 201 is heated to 1200 ° C. under a vacuum of about 0.01 atm in a general low-pressure MOCVD apparatus. The adsorbed material on the surface of the substrate 201 was desorbed to clean the surface.

次に、その清浄化したサファイア基板201の表面上に、一般的な減圧MOCVD法を利用して、層厚を約490nmとする、アンドープでn形の六方晶の単量体BP層202を六方晶燐化硼素系半導体層として形成した。一般的な断面TEM分析によれば、六方晶の単量体BP層202の{0.0.0.2.}結晶面は、サファイア基板201の清浄化された表面に対し垂直に、また、互いに平行に配列しているのが明らかにされた。サファイア基板201の表面において、そのサファイアのc軸の長さに相当する間隔に配列した六方晶のBP層202の{0.0.0.2.}結晶面の面数は6であり、即ち、本発明の云うnは6となった。   Next, an undoped n-type hexagonal monomer BP layer 202 having a layer thickness of about 490 nm is formed on the surface of the cleaned sapphire substrate 201 by using a general low pressure MOCVD method. A boron phosphide-based semiconductor layer was formed. According to a general cross-sectional TEM analysis, {0.0.0.2. } It was revealed that the crystal planes were arranged perpendicular to the cleaned surface of the sapphire substrate 201 and parallel to each other. On the surface of the sapphire substrate 201, {0.0.0.2. Of the hexagonal BP layers 202 arranged at intervals corresponding to the c-axis length of the sapphire. } The number of crystal faces was 6, that is, n in the present invention was 6.

加えて、断面TEM技法及び電子回折手段による観察では、六方晶の単量体BP層202の内部には、双晶の存在は殆ど認められなかった。また、サファイア基板201との接合界面から約30nmを超えてより上方の六方晶の単量体BP層202の内部の領域には、{0.0.0.2.}結晶面の配列上の乱雑さも殆ど確認できず、{0.0.0.2.}結晶面が互いに平行に整然と配列しているのが確認された。   In addition, in the observation by the cross-sectional TEM technique and the electron diffraction means, the presence of twins was hardly observed in the hexagonal monomer BP layer 202. In addition, in the region inside the hexagonal monomer BP layer 202 that is higher than about 30 nm from the bonding interface with the sapphire substrate 201, {0.0.0.2. } Almost no disorder in the arrangement of crystal planes can be confirmed, {0.0.0.2. } It was confirmed that the crystal planes were regularly arranged in parallel with each other.

{0.0.0.2.}結晶面を、層厚の増加方向に平行に配列してなる六方晶の単量体BP層202の表面上には、ゲルマニウム(元素記号:Ge)をドープしたウルツ鉱結晶型で六方晶のn形GaN層(層厚=1900nm)203を六方晶III族窒化物半導体層として成長させた。一般的なTEMを利用した分析によれば、六方晶の単量体BP層203を下地として成長させたこのn形GaN層203は、{0.0.0.1.}結晶面を、六方晶の単量体BP層202の{0.0.0.2.}結晶面と平行として配列なる単結晶層であった。また、六方晶のGaN層203の内部領域には、双晶や積層欠陥は殆ど認められなかった。   {0.0.0.2. } On the surface of the hexagonal monomer BP layer 202 in which the crystal planes are arranged in parallel to the increasing direction of the layer thickness, the wurtzite crystal type doped with germanium (element symbol: Ge) is hexagonal. An n-type GaN layer (layer thickness = 1900 nm) 203 was grown as a hexagonal group III nitride semiconductor layer. According to an analysis using a general TEM, the n-type GaN layer 203 grown using the hexagonal monomer BP layer 203 as a base is {0.0.0.1. } The crystal plane is {0.0.0.2. Of the hexagonal monomer BP layer 202. } It was a single crystal layer arranged parallel to the crystal plane. Also, almost no twins or stacking faults were observed in the internal region of the hexagonal GaN layer 203.

六方晶のn形GaN層203の(1.1.−2.0.)表面上には、六方晶のn形のAl0.15Ga0.85Nからなる下部クラッド層(層厚=150nm)204、Ga0.85In0.15N井戸層とAl0.01Ga0.99N障壁層とを1周期としその5周期からなる多重量子井戸構造の発光層205、及び層厚を50nmとするp形Al0.10Ga0.90Nからなる上部クラッド層206をこの順序で積層し、pn接合型DH構造の発光部を構成した。上記の上部クラッド層206の表面上には、更に、p形のGaN層(層厚=80nm)をコンタクト層207として堆積し、積層構造体200の形成を終了した。 On the (1.1.-2.0.) Surface of the hexagonal n-type GaN layer 203, a lower cladding layer (layer thickness = 150 nm) 204 made of hexagonal n-type Al 0.15 Ga 0.85 N, Ga A 0.85 In 0.15 N well layer and an Al 0.01 Ga 0.99 N barrier layer having one period, and a light emitting layer 205 having a multi-quantum well structure consisting of five periods, and an upper portion made of p-type Al 0.10 Ga 0.90 N having a layer thickness of 50 nm The clad layer 206 was laminated in this order to constitute a light emitting portion having a pn junction type DH structure. A p-type GaN layer (layer thickness = 80 nm) was further deposited as a contact layer 207 on the surface of the upper cladding layer 206, and the formation of the multilayer structure 200 was completed.

上記のp形コンタクト(contact)層207の一部の領域には、金(元素記号:Au)・酸化ニッケル(NiO)合金からなるp形オーミック(Ohmic)電極208を形成した。一方のn形オーミック電極209は、その電極209を設ける領域に在る下部クラッド層204や発光層205等の層をドライエッチング手段で除去した後、露出させたn形GaN層203の表面に形成した。これより、LED20を構成した。   A p-type ohmic electrode 208 made of a gold (element symbol: Au) / nickel oxide (NiO) alloy was formed in a partial region of the p-type contact layer 207. One n-type ohmic electrode 209 is formed on the surface of the exposed n-type GaN layer 203 after the layers such as the lower cladding layer 204 and the light emitting layer 205 in the region where the electrode 209 is provided are removed by dry etching. did. From this, LED20 was comprised.

このLED20のp形及びn形オーミック電極208、209間に、順方向に、20mAの素子駆動電流を通流して、発光特性を調査した。LED20から出射される主たる発光の波長は約460nmであった。チップ(chip)状態での発光光度は約1.8カンデラ(cd)であった。また、pn接合型DH構造の発光部を構成するIII族窒化物半導体からなる各層204〜206や、n形オーミック電極209を設けたn形GaN層203を、六方晶のBP層202上に設けることにより、結晶性に優れるIII族窒化物半導体層から構成できたため、逆方向電流を10μAとした際の逆方向電圧は、15Vを超える高値となった。更に、III族窒化物半導体層の結晶性の良好さにより、局所的な耐圧不良(local breakdown)も殆ど認められないLED20が提供されることとなった。   A 20 mA element drive current was passed in the forward direction between the p-type and n-type ohmic electrodes 208 and 209 of the LED 20 to investigate the light emission characteristics. The wavelength of the main light emitted from the LED 20 was about 460 nm. The luminous intensity in the chip state was about 1.8 candela (cd). Further, the layers 204 to 206 made of a group III nitride semiconductor constituting the light emitting portion of the pn junction type DH structure and the n-type GaN layer 203 provided with the n-type ohmic electrode 209 are provided on the hexagonal BP layer 202. As a result, since the group III nitride semiconductor layer having excellent crystallinity could be formed, the reverse voltage when the reverse current was 10 μA was a high value exceeding 15V. Furthermore, due to the good crystallinity of the group III nitride semiconductor layer, the LED 20 is provided in which almost no local breakdown is observed.

長周期マッチング接合系を説明するための模式図である。It is a schematic diagram for demonstrating a long-period matching joining system. 実施例に記載のLEDの平面模式図である。It is a plane schematic diagram of LED as described in an Example. 図2に示す破線A−A’に沿ったLEDの断面模式図である。FIG. 3 is a schematic cross-sectional view of an LED along a broken line A-A ′ shown in FIG. 2.

符号の説明Explanation of symbols

10 長周期マッチング接合系
11 六方晶単結晶材料
11A 六方晶単結晶材料の表面
11B 六方晶単結晶材料の{0.0.0.1.}結晶面
12 六方晶燐化硼素系半導体層
12A 燐化硼素系半導体層の接合面
12B 六方晶燐化硼素系半導体層の{0.0.0.2.}結晶面
20 化合物半導体LED
200 LED用途積層構造体
201 サファイア基板
202 BP層(六方晶燐化硼素系半導体層)
203 GaN層(六方晶III族窒化物半導体層)
204 下部クラッド層
205 発光層
206 上部クラッド層
207 コンタクト層
208 p形オーミック電極
209 n形オーミック電極
d 六方晶燐化硼素系半導体層の{0.0.0.2.}結晶面の面間隔
10 Long-Period Matching Junction System 11 Hexagonal Single Crystal Material 11A Surface of Hexagonal Single Crystal Material 11B Hexagonal Single Crystal Material {0.0.0.1. } Crystal plane 12 Hexagonal boron phosphide-based semiconductor layer 12A Bonding surface of boron phosphide-based semiconductor layer 12B Hexagonal boron phosphide-based semiconductor layer {0.0.0.2. } Crystal face 20 Compound semiconductor LED
200 Laminated structure for LED 201 sapphire substrate 202 BP layer (hexagonal boron phosphide-based semiconductor layer)
203 GaN layer (hexagonal group III nitride semiconductor layer)
204 Lower clad layer 205 Light emitting layer 206 Upper clad layer 207 Contact layer 208 p-type ohmic electrode 209 n-type ohmic electrode d of hexagonal boron phosphide-based semiconductor layer {0.0.0.2. } Surface spacing of crystal planes

Claims (2)

単結晶材料の表面に接合させて設けた燐化硼素系半導体層を備えてなる化合物半導体素子において、
上記単結晶材料は六方晶でその層厚の増加方向に略平行に{0.0.0.1.}結晶面が配列され、
上記燐化硼素系半導体層は、{0.0.0.2.}結晶面が上記単結晶材料の表面に略垂直に配列されるとともに、その{0.0.0.2.}結晶面の連続するn個分(nは2以上の正の整数)の距離が、単結晶材料のc軸の長さと略同等である、
ことを特徴とする化合物半導体素子。
In a compound semiconductor element comprising a boron phosphide-based semiconductor layer provided bonded to the surface of a single crystal material,
The single crystal material is hexagonal and substantially parallel to the increasing direction of the thickness {0.0. } The crystal faces are arranged,
The boron phosphide-based semiconductor layer has {0.0.0.2. } The crystal plane is arranged substantially perpendicular to the surface of the single crystal material and {0.0. } The distance of n consecutive crystal planes (n is a positive integer of 2 or more) is approximately equal to the length of the c-axis of the single crystal material.
The compound semiconductor element characterized by the above-mentioned.
上記{0.0.0.2.}結晶面の個数nを6以下とする、請求項1に記載の化合物半導体素子。   Above {0.0.0.2. } The compound semiconductor device according to claim 1, wherein the number n of crystal faces is 6 or less.
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