JP4084506B2 - Manufacturing method of semiconductor light emitting device - Google Patents

Description

【００４８】
ここで、νは ポアソン比（ν ＝ Ｃ₁₂／（Ｃ₁₁＋Ｃ₁₂）；Ｃ₁₁，Ｃ₁₂は弾性スティフネス定数である）、αは界面でのバーガースベクトルと転位線の線分とのなす角（ｃｏｓ α ＝ １／２）、λは滑り面と界面の交差線に垂直な界面内での方向とバーガースベクトルとのなす角（ｃｏｓ λ ＝ １／２）、ｂ＝ ａ／２^1/2 （ａ；格子定数）、ｆは格子不整合度（ｆ ＝ Δａ／ａ）である。なお、数１は無限大の厚さの基板上に単層膜を成長する場合の式であり、以後、この式(数１)によって与えられる臨界膜厚ｈ_cを、Ｍａｔｔｈｅｗｓａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づく臨界膜厚と称す。
【００４９】
図１４には、一般に支持されているＭａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づいて計算されたＧａＡｓ基板上のＧａＩｎＡｓ層の臨界膜厚が示されている。なお、Ｇａ_1-xＩｎ_xＡｓに窒素を添加したＧａ_1-xＩｎ_xＮＡｓの格子定数は、窒素添加１％当たり、Ｉｎ組成ｘが３％小さいＧａ_1-yＩｎ_yＡｓ（ｙ＝ｘ−０．０３）とほぼ同じ格子定数となる。
【００５０】
ＧａＡｓ基板上にＧａＩｎＡｓを形成する場合、Ｉｎ組成を増加すると歪み量が大きくなるので、平面に２次元で成長できる膜厚である臨界膜厚は薄くなっていく。
【００５１】
これに対し、本願の発明者は、ＧａＡｓ基板上のＧａＩｎＡｓ量子井戸層においてＩｎ組成を３０％を超える値とすることにより、ＧａＡｓ基板に対する量子井戸層の歪み量を２％以上で成長でき、従来限界と考えられてきた１．１μｍ より長波長の半導体発光素子（半導体レーザ）が実現可能であることを見出した。更には、歪み量子井戸層２において、低温成長等の非平衡条件での成長により実質的な臨界膜厚ｈ_c’を、Ｍａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの臨界膜厚ｈ_cを越えた厚さとすることが可能であり、これにより、１．２μｍを越える長波長までの半導体発光素子（半導体レーザ）が実現可能であることを見出した。
【００５２】
すなわち、本願の発明者は、半導体基板上に、歪み量子井戸層を含む活性層と、光とキャリアを閉じ込めるクラッド層とが形成されている半導体発光素子において，半導体基板及びクラッド層に対する前記歪み量子井戸層の厚さがＭａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づく臨界膜厚ｈ_cより厚い場合に、従来得られない波長の半導体レーザ等の半導体発光素子を得ることができ、また、従来より高性能のＨＥＭＴ(high electron mobility transister)等の電子素子を得ることもできることを見出した。
【００５３】
図１４には実験例が示されている。図１４を参照すると、例えば、Ｉｎ組成３２％、厚さ８．６ｎｍの場合、ＰＬ中心波長は１．１３μｍであり、また、Ｉｎ組成３６％、厚さ７．８ｎｍの場合、ＰＬ中心波長は１．１６μｍであり、また、 Ｉｎ組成３９％、厚さ７．２ｎｍの場合、ＰＬ中心波長は１．２μｍであった。これらは、Ｍａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論（数１）に基づいて計算した臨界膜厚ｈ_cを越えた厚さとなっている。
【００５４】
図１５には、ＧａＩｎＡｓ単一量子井戸層からのＰＬ中心波長とＰＬ強度との関係が示されている。ＧａＩｎＡｓ井戸層（図中実線部）のＩｎ組成ｘは３１％〜４２％とした。また、各井戸層２５ａ，２５ｂの厚さは、Ｉｎ組成ｘの増加に合わせて、約９ｎｍ〜約６ｎｍと薄くしていった。波長１．２μｍ程度までＰＬ強度の強い量子井戸層が得られた。波長１．２μｍまではＰＬ強度は徐々に低下しているのに対して、１．２μｍを越えると、ＰＬ強度は急激に低下していることがわかる。これは表面性にも対応しており１．２μｍまでは鏡面であった。これらの結果から、ＰＬ強度の上記急激な低下は量子井戸層の厚さが実質的な臨界膜厚ｈ_c’を越えたためと考えられる。一般にＭＯＣＶＤ法やＭＢＥ法において低温成長、高い成長速度等の強い非平衡成長条件で、実験的に得られる臨界膜厚が増加することが報告されている。また成長条件（例えば高温成長）により、理論に基づく臨界膜厚より薄い厚さでも三次元成長、表面荒れが起こることも報告されている。よって本結果は、理論に基づく臨界膜厚ｈ_cよりも低温成長等の非平衡条件での成長による実質的な臨界膜厚ｈ_c’の方が厚いために、ミスフィット転位が生じることなく、より厚い膜を二次元に成長できたものと考えられる。
【００５５】
さらに、本願の発明者は、ＧａＩｎＮＡｓレーザの場合、上記のようにＩｎ組成ｘを大きくすることにより窒素組成を小さくできるため、ＧａＩｎＮＡｓレーザの特性を大きく改善できることを見出した。
【００５６】
また、レーザ化する場合、クラッド層としてＡｌＧａＡｓを用いるよりＧａＩｎＰ(Ａｓ)を用いた方が容易に形成できることを見出した。その理由を以下に示す。
【００５７】
すなわち、大きな歪みを有したＧａＩｎＮＡｓやＧａＩｎＡｓ活性層は低温(例えば６００℃以下)で成長できる。しかしＡｌＧａＡｓの成長温度は一般に高い(例えば７００℃以上)。本願の発明者は、活性層成長後に、活性層の上部にＡｌＧａＡｓクラッド層を成長することを想定して熱処理実験を行なった。具体的に、(１００)ＧａＡｓ基板上に、ＧａＡｓ層(膜厚が０．２μｍ)，ＧａＩｎＮＡｓ井戸層(膜厚が７ｎｍ)，ＧａＡｓ層(膜厚が５０ｎｍ)を順次に成長させた試料を４試料(ａ，ｂ，ｃ，ｄ)作製した。４つの各試料ａ，ｂ，ｃ，ｄは、Ｉｎ組成は同じで窒素組成が違う。すなわち、試料ａの窒素(Ｎ)組成は０．２％であり、試料ｂの窒素(Ｎ)組成は０．２％であり、試料ｃの窒素(Ｎ)組成は０．５％であり、試料ｄの窒素(Ｎ)組成は０．８％である。その後、ＭＯＣＶＤ成長装置を用いてＡｓＨ₃雰囲気中で、試料ｃ，ｄについては６８０℃の温度で、また、試料ｂについては７００℃の温度で、また、試料ａについては７８０℃の温度で、３０分間熱処理(アニ−ル)した。図１２には、これらの試料ａ，ｂ，ｃ，ｄのＰＬ特性が示されている。図１２において、点線が熱処理前のスペクトルであり、実線が熱処理後のスペクトルである。熱処理によりピーク波長が短波長側にシフトし、熱処理温度が高い方がシフト量が大きいことがわかる。同じ温度では、窒素量が違う試料間(試料ｃ，試料ｄ)でシフト量は同じであり、このシフトの原因はＩｎの拡散であると考えられる。また、発光強度は、７８０℃では低下しており、７００℃以下では増加していることがわかる。発光強度の増加の原因は熱処理による活性層中の欠陥の減少と考えられ、低下の原因は結晶性の劣化と考えられる。
【００５８】
このように大きな歪みを有したＧａＩｎＮＡｓやＧａＩｎＡｓ活性層を成長してから７８０℃のような高温で上部の層(例えばクラッド層)を成長すると不具合が生じることがわかった。このため上部クラッド層としては低温で良好に成長できるＧａＩｎＰ(Ａｓ)が好ましい。ただしＡｌＧａＡｓでも７００℃以下の温度で成長すれば大きな問題はないので使用できる。
【００５９】
もう一つの理由は、大きな歪みを有したＧａＩｎＮＡｓやＧａＩｎＡｓ活性層を成長する前にＡｌＧａＡｓを成長すると活性層の品質を落しやすいことである。本願の発明者は、(１００)ＧａＡｓ基板上に、ガイド層(膜厚が０．２μｍ)，ＧａＡｓ層(膜厚が１００ｎｍ)，ＧａＩｎＮＡｓ井戸層(膜厚が７ｎｍ)，ＧａＡｓ層(膜厚が１００ｎｍ)，ガイド層(膜厚が５０ｎｍ)を順次成長した試料を２試料作製した。第１の試料は、ガイド層(クラッド層)としてＧａ_0.5Ｉｎ_0.5Ｐを用い(以下、ＧａＩｎＰを用いた試料と称す)、また、第２の試料は、ガイド層(クラッド層)としてＡｌ_0.4Ｇａ_0.6Ａｓを用いた(以下、ＡｌＧａＡｓを用いた試料と称す)。ＧａＩｎＰを用いた試料の方がＩｎ組成は大きく歪みが大きくなっている。図１３には第１の試料(ＧａＩｎＰ)，第２の試料(ＡｌＧａＡｓ)のＰＬ特性が示されている。図１３から、ＧａＩｎＰを用いた試料の方が歪みが大きく長波長であり、成長が困難であるにもかかわらず、ＡｌＧａＡｓを用いた試料よりもＰＬ強度が強くなっていることがわかる。
【００６０】
この原因としてはＡｌに起因した欠陥が成長中に成長表面に現れ、常に成長表面に伝搬し、ＧａＩｎＮＡｓ井戸層まで到達し、井戸層を劣化させていることが考えられる。つまり、量子井戸活性層の成長直前のエピ基板表面の状態が良好でないと高品質に成長できないことがわかった。このため下部クラッド層としてＡｌＧａＡｓを用いる場合は井戸層成長の前にこの欠陥を止める工夫をする必要がある。半導体基板と活性層との間のクラッド層としてＡｌを含まないＧａＩｎＰ(Ａｓ)を用いると、量子井戸活性層の成長直前のエピ基板表面の状態は良好であり、大きい歪みの量子井戸層を容易に良好に成長できる。上述したようにクラッド層としては、特に、半導体基板と大きい歪みの活性層との間の下部クラッド層としては、ＧａＩｎＰ(Ａｓ)を用いる方が好ましいことがわかる。
【００６１】
さらに、本願の発明者は、ＧａＡｓ基板の面方位は、(１００)から大きく傾いている(例えば、(１００)から［０１１］方向に大きく傾いている)よりは、(１００)付近の方がＩｎ組成を大きくし易いし、発光効率を高くし易く適していることを見出した。光通信で用いる１．３μｍ帯等の長波長での高品質なＧａＩｎＮＡｓを得るための１つの方法は、ＧａＩｎＮＡｓにおいて、Ｉｎ組成を大きくして長波長化し、窒素組成を減らすことである。ＧａＡｓ基板の面方位が(１００)である場合と、基板の面方位が(１００)から［０１１］方向に１５°の角度で傾いている場合とのそれぞれの場合において、ＧａＡｓ基板上に、Ｇａ_0.5Ｉｎ_0.5Ｐ層(膜厚が０．２μｍ)と、ＧａＡｓ層(膜厚が１００ｎｍ)と、ＧａＩｎＮＡｓ量子井戸層(発光層)(膜厚が７ｎｍ)およびＧａＡｓバリア層(膜厚が１３ｎｍ)からなる活性層と、ＧａＡｓ層(膜厚が１００ｎｍ)と、Ｇａ_0.5Ｉｎ_0.5Ｐ層(膜厚が５０ｎｍ)と、ＧａＡｓ層(膜厚が５０ｎｍ)とを順次に形成した。図３には、面方位が(１００)であるＧａＡｓ基板上に形成された半導体発光素子のＰＬ特性(符号Ａで示す)と、面方位が(１００)から〔０１１〕方向に１５゜の角度で傾いているＧａＡｓ基板上に形成された半導体発光素子のＰＬ特性(符号Ｂで示す)を示す。なお、面方位が(１００)から〔０１１〕方向に１５゜の角度で傾いているＧａＡｓ基板上に形成された半導体発光素子では、ＰＬ波長１．０６μｍのＧａＩｎＡｓに窒素添加している。一方、面方位が(１００)であるＧａＡｓ基板上に形成された半導体発光素子では、ＰＬ波長１．１３μｍのＧａＩｎＡｓに窒素添加している。
【００６２】
図３から面方位が(１００)であるＧａＡｓ基板上に形成された半導体発光素子の方が、長波長であるにもかかわらず発光強度が高くなっており、適していることがわかる。これに対し、面方位が(１００)から〔０１１〕方向に１５°の角度で傾いているＧａＡｓ基板上に形成された半導体発光素子では、Ｉｎ組成を大きくし１．０６μｍの波長よりも長波長化を試みたが、発光強度は著しく低下し、Ｉｎ組成を大きくすることは困難であった。一方、面方位が(１００)であるＧａＡｓ基板上に形成された半導体発光素子では、ＧａＩｎＡｓを用いて１．２μｍ程度の波長まで強い発光が観察された。このことから、ＧａＡｓ基板の面方位の(１００)からの傾き角度は、５°の範囲内であるのが好ましい。
【００６３】
【実施例】
次に、実施例について説明する。
実施例１
図４は実施例１の半導体発光素子を示す図である。ここでは、半導体発光素子として、最も簡単な構造である絶縁膜ストライプ型レーザを例にして説明する。図４の半導体発光素子は、層構造として、ＳＣＨ−ＤＱＷ(Separate Confinement Heterostructure Double Quantum Well)構造を有している。具体的に、図４の半導体発光素子は、面方位(１００)のｎ−ＧａＡｓ基板２１上に、ｎ−ＧａＡｓバッファ層２２と、ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層２３(膜厚が１．５μｍ)と、ＧａＡｓ光ガイド層２４(膜厚が１００ｎｍ)と、Ｇａ_1-xＩｎ_xＡｓ井戸層２５ａ，２５ｂおよびＧａＡｓバリア層２６(膜厚が１３ｎｍ)からなる活性層(発光層)２７と、ＧａＡｓ光ガイド層２８(膜厚が１００ｎｍ)と、ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層２９(膜厚が１．５μｍ)と、ｐ−ＧａＡｓコンタクト層３０(膜厚が０．３μｍ)とが、順次に形成されている。また、図４の半導体発光素子では、ＧａＡｓコンタクト層３０は電流注入部分以外はエッチングにより除去され、電流注入部となる部分を除去した絶縁膜３１を介してｐ側電極３２が形成されている。また、基板２１の裏面にはｎ側電極３３が形成されている。
【００６４】
ここで、Ｇａ_1-xＩｎ_xＡｓ井戸層２５ａ，２５ｂのＩｎ組成ｘは３１％〜４２％とした。また、各井戸層２５ａ、２５ｂの厚さは、Ｉｎ組成の増加に合わせて、約９ｎｍ〜約６ｎｍと薄くしていった。これらのレーザの量子井戸層厚さは、Ｍａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づく臨界膜厚ｈ_cよりも厚い条件となっている。例えば、Ｉｎ組成３２％、厚さ８．６ｎｍの場合、発振波長は１．１３μｍであり、また、Ｉｎ組成３６％、厚さ７．８ｎｍの場合、発振波長は１．１６μｍであり、また、 Ｉｎ組成３９％、厚さ７．２ｎｍの場合、発振波長は１．２μｍであった。また、各井戸層２５ａ，２５ｂの圧縮歪み量は、組成に応じて変化し、約２．２％〜２．７％であった。
【００６５】
図４の半導体発光素子の各層の成長方法はＭＯＣＶＤ法で行なった。その原料にはＴＭＧ(トリメチルガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)を用い、キャリアガスにはＨ₂を用いた。また、ＧａＩｎＡｓ層は５５０℃で成長した。
【００６６】
図５には、図４の半導体発光素子の発振波長に対するしきい電流密度Ｊ_thが示されている。図５から、図４の半導体発光素子の発振波長は１．１３〜１．２３μｍであり、従来のＧａＡｓ基板上に成長したＧａＩｎＡｓ量子井戸レーザ素子に比べて発振波長が長波長化できていることがわかる。また、発振波長が１．２μｍを越えると急激にしきい値が上昇するが、１．２μｍ程度までは、しきい電流密度Ｊ_thは２００Ａ／ｃｍ²程度であり，充分低いこともわかる。また、高温での特性も良好であった。
【００６７】
なお、上述の例では、半導体発光素子の成長を、ＭＯＣＶＤ法で行なったが、ＭＢＥ法等、他の成長方法を用いることもできる。また、図４の半導体発光素子では、活性層(発光層)の積層構造として、二重量子井戸構造(ＤＱＷ)の例を示したが、他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)を用いることもできる。また、各層の組成厚さ等は、必要に応じて、変更設定できる。また、クラッド層には、ＧａＩｎＰ（Ａｓ）と同様のワイドギャップのＡｌＧａＡｓを用いることもできる。また、レーザの構造も他の構造にしても良い。ただし、ＧａＡｓ基板の面方位については、(１００)付近が良く、面方位の(１００)からの傾き角度は５°の範囲内が好ましい。また、ＭＯＣＶＤ法等で面方位(１００)または少し傾いた(１００)基板上にＧａＩｎＰを成長するとヒロックと呼ばれる丘状欠陥が形成されやすい。これは素子の歩留り低下や発光効率低下などの悪影響を招き好ましくない。成長条件の最適化でヒロック密度を低減できるが、Ａｓを含ませたＧａＩｎＰＡｓとすることで容易に低減できる。Ａｓ組成はわずかでも効果があり、好ましい。
【００６８】
実施例２
図６は実施例２の半導体発光素子を示す図である。ここでは、半導体発光素子として、最も簡単な構造である絶縁膜ストライプ型レーザを例にして説明する。図６の半導体発光素子は、層構造として、ＳＣＨ−ＤＱＷ(Separate Confinement Heterostructure Double Quantum Well)構造を有している。具体的に、図６の半導体発光素子は、面方位(１００)のｎ−ＧａＡｓ基板４１上に、ｎ−ＧａＡｓバッファ層４２と、ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層４３(膜厚が１．５μｍ)と、ＧａＡｓ光ガイド層４４(膜厚が１００ｎｍ)と、Ｇａ_0.67Ｉｎ_0.33Ｎ_0.006Ａｓ_0.994井戸層４５ａ，４５ｂおよびＧａＡｓバリア層４６(膜厚が１３ｎｍ)からなる活性層(発光層)４７と、ＧａＡｓ光ガイド層４８(膜厚が１００ｎｍ)と、ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層４９(膜厚が１．５μｍ)と、ｐ−ＧａＡｓコンタクト層５０(膜厚が０．３μｍ)とが、順次に形成されている。また、図６の半導体発光素子では、ＧａＡｓコンタクト層５０は電流注入部分以外はエッチングにより除去され、電流注入部となる部分を除去した絶縁膜５１を介してｐ側電極５２が形成されている。また、基板４１の裏面にはｎ側電極５３が形成されている。
【００６９】
ここで、各井戸層４５ａ，４５ｂのＩｎ組成ｘは３３％、窒素(Ｎ)組成は０．６％とした。また、各井戸層４５ａ，４５ｂの厚さは７ｎｍとした。また、各井戸層４５ａ，４５ｂの圧縮歪み量は約２．３％であった。
【００７０】
図６の半導体発光素子の各層の成長方法はＭＯＣＶＤ法で行なった。その原料にはＴＭＧ(トリメチルガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)を用い、そして窒素の原料にはＤＭＨｙ(ジメチルヒドラジン)を用いた。ＤＭＨｙは低温で分解するので６００℃以下のような低温成長に適している。また、特に、歪みの大きい量子井戸層を成長する場合は例えば５００℃〜６００℃程度の低温成長が好ましい。すなわち、ＤＭＨｙは低温で分解するので６００℃以下のような低温成長に適しており、特に低温成長の必要な歪みの大きい量子井戸層を成長する場合好ましい。いまの例では、ＧａＩｎＮＡｓ井戸層４５ａ，４５ｂは５５０℃で成長した。また、キャリアガスにはＨ₂を用いた。
【００７１】
図７には、図６の半導体発光素子の連続動作での電流−出力パワー(電圧)特性が示されている。ここで、しきい電流密度Ｊ_thは５７０Ａ／ｃｍ²であった。また、発振波長は約１．２４μｍであった。図６の半導体発光素子では、井戸層４５ａ，４５ｂのＩｎ組成を３０％より大きくし、圧縮歪み量を２％以上にしたことにより、従来のＧａＩｎＮＡｓレーザ素子に比べて、しきい電流密度Ｊ_thを劇的に低減できた。また、高温での特性も良好であった。また、発振波長は、窒素組成，Ｉｎ組成，および井戸層の厚さ等の制御で可変である。
【００７２】
なお、上述の例では、半導体発光素子の成長を、ＭＯＣＶＤ法で行なったが、ＭＢＥ法等他の成長方法を用いることもできる。また、図６の半導体発光素子では、井戸層４５ａ，４５ｂの窒素(Ｎ)の原料に、ＤＭＨｙを用いたが、活性化した窒素やＮＨ₃等他の窒素化合物を用いることもできる。また、図６の半導体発光素子では、活性層(発光層)の積層構造として２重量子井戸構造(ＤＱＷ)の例を示したが、他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)を用いることもできる。また、各層の組成厚さ等は、必要に応じて、変更設定できる。また、クラッド層には、ＧａＩｎＰ（Ａｓ）と同様のワイドギャップのＡｌＧａＡｓを用いることもできる。また、レーザの構造も他の構造にしても良い。
【００７３】
実施例３
図８は実施例３の半導体発光素子を示す図である。ここでは、半導体発光素子として、最も簡単な構造である絶縁膜ストライプ型レーザを例にして説明する。図８の半導体発光素子は、層構造として、ＳＣＨ−ＤＱＷ(Separate Confinement Heterostructure Double Quantum Well)構造を有している。実施例３の図８の半導体発光素子は、実施例２の図６とほぼ同様の構造となっているが、ｎ−ＧａＡｓ基板４１の面方位が(１００)から［０１１］方向に２°の角度で傾いたものとなっている。また、井戸層の組成等が実施例２と相違している。
【００７４】
すなわち、図８の半導体発光素子は、面方位が(１００)から［０１１］方向に２°の角度で傾いたｎ−ＧａＡｓ基板６１上に、ｎ−ＧａＡｓバッファ層６２と、ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層６３(膜厚が１．５μｍ)と、ＧａＡｓ光ガイド層６４(膜厚が１００ｎｍ)と、Ｇａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995井戸層６５ａ，６５ｂおよびＧａＡｓバリア層６６(膜厚が１３ｎｍ)からなる活性層(発光層)６７と、ＧａＡｓ光ガイド層６８(膜厚が１００ｎｍ)と、ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層６９(膜厚が１．５μｍ)と、ｐ−ＧａＡｓコンタクト層７０(膜厚が０．３μｍ)とが、順次に形成されている。また、図８の半導体発光素子では、ＧａＡｓコンタクト層７０は電流注入部分以外はエッチングにより除去され、電流注入部となる部分を除去した絶縁膜７１を介してｐ側電極７２が形成されている。また、基板６１の裏面にはｎ側電極７３が形成されている。
【００７５】
ここで、各井戸層６５ａ，６５ｂのＩｎ組成ｘは４０％，窒素(Ｎ)組成は０．５％とした。また、各井戸層６５ａ，６５ｂの厚さは７ｎｍとした。これはＭａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づく臨界膜厚ｈ_c（約６．１ｎｍ）よりも厚い条件となっている。また、各井戸層６５ａ，６５ｂの圧縮歪み量は約２．７％であった。
【００７６】
図８の半導体発光素子の各層の成長方法はＭＯＣＶＤ法で行なった。その原料にはＴＭＧ(トリメチガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)を用い、そして窒素の原料にはＤＭＨｙ(ジメチルヒドラジン)を用いた。ＤＭＨｙは低温で分解するので６００℃以下のような低温成長に適している。また、特に、歪みの大きい量子井戸層を成長する場合は、例えば５００℃〜６００℃程度の低温成長が好ましい。いまの例では、ＧａＩｎＮＡｓ井戸層６５ａ，６５ｂは５４０℃で成長した。また、キャリアガスにはＨ₂を用いた。
【００７７】
このように作製した図８の半導体発光素子の発振波長は約１．３μｍであった。また、しきい電流密度Ｊ_thは１ｋＡ／ｃｍ²以下であった。ＧａＩｎＮＡｓレーザは，窒素組成が大きくなるほどしきい電流密度が大きくなる傾向がある。従来の１．３μｍ帯のＧａＩｎＮＡｓレーザ素子においては窒素組成は小さくしても１％(Ｉｎ組成が３０％の時)であったが、本発明では、Ｉｎ組成を３０％より大きくし、圧縮歪み量を２％以上にしたことにより、従来より窒素組成を小さくでき、しきい電流密度を劇的に低減できた。また、高温での特性も良好であった。
【００７８】
なお、上述の例では、半導体発光素子の成長を、ＭＯＣＶＤ法で行なったが、ＭＢＥ法等他の成長方法を用いることもできる。また、図８の半導体発光素子では、井戸層６５ａ，６５ｂの窒素(Ｎ)の原料に、ＤＭＨｙを用いたが、活性化した窒素やＮＨ₃等他の窒素化合物を用いることもできる。また、図８の半導体発光素子では、活性層(発光層)の積層構造として２重量子井戸構造(ＤＱＷ)の例を示したが、他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)を用いることもできる。また、各層の組成厚さ等は、必要に応じて、変更設定できる。また、クラッド層には、ＧａＩｎＰ（Ａｓ）と同様のワイドギャップのＡｌＧａＡｓを用いることもできる。また、レーザの構造も他の構造にしても良い。
【００７９】
実施例４
図９は実施例４の半導体発光素子を示す図である。ここでは、半導体発光素子として、最も簡単な構造である絶縁膜ストライプ型レーザを例にして説明する。図９の半導体発光素子は、層構造として、ＳＣＨ−ＤＱＷ(Separate Confinement Heterostructure Double Quantum Well)構造を有している。具体的に、図９の半導体発光素子は、面方位が(１００)から［０１１］方向に５°の角度で傾いたｎ−ＧａＡｓ基板８１上に、ｎ−ＧａＡｓバッファ層８２と、ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層８３(膜厚が１．５μｍ)と、ＧａＡｓ光ガイド層８４(膜厚が１００ｎｍ)と、Ｇａ_0.65Ｉｎ_0.35Ｎ_0.007Ａｓ_0.993井戸層８５ａ，８５ｂと井戸層８５ａ，８５ｂの間および井戸層８５ａの下方および井戸層８５ｂの上方に設けられたＧａＮＰＡｓバリア層８６ａ，８６ｂ，８６ｃ(各膜厚が１０ｎｍ)とが形成されている活性層(発光層)８７と、ＧａＡｓ光ガイド層８８(膜厚が１００ｎｍ)と、ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層８９(膜厚が１．５μｍ)と、ｐ−ＧａＡｓコンタクト層９０(膜厚が０．３μｍ)とが順次に形成されている。また、図９の半導体発光素子では、ＧａＡｓコンタクト層９０は電流注入部分以外はエッチングにより除去され、電流注入部となる部分を除去した絶縁膜９１を介してｐ側電極９２が形成されている。また、基板９１の裏面にはｎ側電極９３が形成されている。
【００８０】
ここで、各井戸層８５ａ，８５ｂのＩｎ組成ｘは３５％，窒素(Ｎ)組成は０．７％とした。また、各井戸層８５ａ，８５ｂの厚さは７ｎｍとした。また、各井戸層８５ａ，８５ｂの圧縮歪み量は約２．４％であった。この際、バリア層８６ａ，８６ｂ，８６ｃは引っ張り歪を有しており、井戸層８５ａ，８５ｂの圧縮みを緩和している。
【００８１】
図９の半導体発光素子の各層の成長方法はＭＯＣＶＤ法で行なった。その原料にはＴＭＧ(トリメチガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)を用い、そして窒素の原料にはＤＭＨｙ(ジメチルヒドラジン)を用いた。ＤＭＨｙは低温で分解するので６００℃以下のような低温成長に適している。また、特に、歪みの大きい量子井戸層を成長する場合は、例えば５００℃〜６００℃程度の低温成長が好ましい。いまの例では、ＧａＩｎＮＡｓ層は５２０℃で成長した。また、キャリアガスにはＨ₂を用いた。
【００８２】
このように作製した図９の半導体発光素子の発振波長は約１．３μｍであった。また、しきい電流密度Ｊ_thは１ｋＡ／ｃｍ²以下であった。ＧａＩｎＮＡｓレーザは，窒素組成が大きくなるほどしきい電流密度が大きくなる傾向がある。従来の１．３μｍ帯のＧａＩｎＡｓレーザ素子においては窒素組成は小さくしても１％(Ｉｎ組成が３０％の時)であったが、本発明では、Ｉｎ組成を３０％より大きくし、圧縮歪み量を２％以上にしたことにより、従来より窒素組成を小さくでき、しきい電流密度を劇的に低減できた。さらに、実施例４では、井戸層８５ａ，８５ｂの圧縮歪みを緩和する引っ張り歪みを有するバリア層８６ｂ，８６ｃがさらに設けられているので、実施例３の素子よりもしきい電流密度は低減した。また、高温での特性も良好であった。
【００８３】
なお、上述の例では、半導体発光素子の成長を、ＭＯＣＶＤ法で行なったが、ＭＢＥ法等他の成長方法を用いることもできる。また、図９の半導体発光素子では、井戸層８５ａ，８５ｂの窒素(Ｎ)の原料に、ＤＭＨｙを用いたが、活性化した窒素やＮＨ₃等他の窒素化合物を用いることもできる。また、図９の半導体発光素子では、活性層(発光層)の積層構造として２重量子井戸構造(ＤＱＷ)の例を示したが、他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)を用いることもできる。また、各層の組成厚さ等は、必要に応じて、変更設定できる。また、クラッド層には、ＧａＩｎＰ（Ａｓ）と同様のワイドギャップのＡｌＧａＡｓを用いることもできる。また、レーザの構造も他の構造にしても良い。
【００８４】
実施例５
図１０は実施例５の半導体発光素子(半導体レーザ)を示す図である。図１０に示す半導体発光素子は面発光型である。この半導体発光素子は、発光を得るための共振器を構成するため、量子井戸活性層１０４の半導体基板１０１とは反対の側には上部反射鏡１０９が形成され、また、量子井戸活性層１０４の半導体基板１０１側には下部反射鏡１０２が形成されており、上部反射鏡１０９と下部反射鏡１０２のうちの少なくとも下部反射鏡１０２は、Ａｌを含まない材料による低屈折率層と高屈折率層とが交互に積層された半導体多層膜として構成されている。この構成では、上部反射鏡１０９，下部反射鏡１０２は、量子井戸活性層１０４からの発光に対する共振器として機能するようになっている。
【００８５】
より具体的に、図１０の半導体発光素子は、面方位(１００)のｎ−ＧａＡｓ基板１０１上に、ＧａＡｓ基板１０１に格子整合するｎ−Ｇａ_0.5Ｉｎ_0.5Ｐとｎ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(３５周期)からなるｎ−半導体多層膜反射鏡(ＧａＩｎＰ／ＧａＡｓ下部半導体多層膜反射鏡)１０２，ＧａＡｓスペーサ層１０３，３層のＧａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995Ａｓ井戸層とＧａＡｓバリア層(１３ｎｍ)からなる多重量子井戸活性層(ＧａＩｎＮＡｓ／ＧａＡｓ ＱＷ活性層)１０４，ＧａＡｓスペーサ層１０５，Ａｌ_xＯ_y電流狭さく層１０６，電流注入部としてのｐ−ＡｌＡｓ層１０７(膜厚が５０ｎｍ)，ｐ−ＧａＡｓコンタクト層１０８，ＧａＡｓ基板１０１に格子整合するｐ−Ｇａ_0.5Ｉｎ_0.5Ｐとｐ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(３０周期)からなるｐ−半導体多層膜反射鏡(ＧａＩｎＰ／ＧａＡｓ上部半導体多層膜反射鏡)１０９が順次に成長されている。
【００８６】
また、ＧａＡｓスペ−サ層１０３，量子井戸活性層１０４，ＧａＡｓスペ−サ層１０５，電流狭さく層１０６，ｐ−ＧａＡｓコンタクト層１０８の側面には、絶縁膜(ポリイミド)１１０が形成され、また、ｐ−ＧａＡｓコンタクト層１０８上にはｐ側電極１１１が形成され、また、ＧａＡｓ基板１０１の裏面にはｎ側電極１１２が形成されている。
【００８７】
図１０の半導体発光素子を次のように作製した。すなわち、先ず、面方位(１００)のｎ−ＧａＡｓ基板１０１上に、ＧａＡｓ基板１０１に格子整合するｎ−Ｇａ_0.5Ｉｎ_0.5Ｐとｎ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(３５周期)からなるｎ−半導体多層膜反射鏡(ＧａＩｎＰ／ＧａＡｓ下部半導体多層膜反射鏡)１０２，ＧａＡｓスペーサ層１０３，３層のＧａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995Ａｓ井戸層とＧａＡｓバリア層(１３ｎｍ)からなる多重量子井戸活性層(ＧａＩｎＮＡｓ／ＧａＡｓ ＱＷ活性層)１０４，ＧａＡｓスペーサ層１０５，Ａｌ_xＯ_y電流狭さく層１０６，電流注入部としてのｐ−ＡｌＡｓ層１０７(膜厚が５０ｎｍ)，ｐ−ＧａＡｓコンタクト層１０８，ＧａＡｓ基板１０１に格子整合するｐ−Ｇａ_0.5Ｉｎ_0.5Ｐとｐ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(３０周期)からなるｐ−半導体多層膜反射鏡(ＧａＩｎＰ／ＧａＡｓ上部半導体多層膜反射鏡)１０９を順次成長させた。
【００８８】
ここで、井戸層のＩｎ組成ｘは４０％，窒素組成は０．５％とした。また、井戸層の厚さは７ｎｍとした。これはＭａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づく臨界膜厚ｈ_c（約６．１ｎｍ）よりも厚い条件となっている。また、圧縮歪量は約２．７％であった。成長方法はＭＯＣＶＤ法で行なった。原料にはＴＭＧ(トリメチルガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)，そして窒素の原料にはＤＭＨｙ(ジメチルヒドラジン)を用いた。
【００８９】
ＤＭＨｙは低温で分解するので、６００℃以下のような低温成長に適している。また、歪みの大きい量子井戸層を成長する場合は例えば５００℃〜６００℃程度の低温成長が好ましい。この実施例５では、ＧａＩｎＮＡｓ層は５４０℃で成長した。ＤＭＨｙは低温で分解するので、６００℃以下のような低温成長に適しており、特に低温成長の必要な歪みの大きい量子井戸層を成長する場合には好ましい。また、キャリアガスにはＨ₂を用いた。
【００９０】
そして、フォトリソグラフィ−とエッチング工程により下部多層膜反射鏡１０２の上部まで直径３０μｍの円形にメサエッチングし、更に上部多層膜反射鏡１０９のみを直径１０μｍの円形にメサエッチングした。Ａｌ_xＯ_y電流狭さく部１０６は側面の現れたＡｌＡｓを水蒸気で側面から酸化して形成した。
【００９１】
次に、絶縁膜(ポリイミド)１１０でエッチング部を埋め込んで平坦化し、ｐ側電極１１１が形成されるべき部分と光取り出し口となる上部多層膜反射鏡１０９上のポリイミドを除去し、ｐ−ＧａＡｓコンタクト層１０８上にｐ側電極１１１を形成し、基板１０１の裏面にはｎ側電極１１２を形成した。
【００９２】
図１０の半導体発光素子では、半導体基板１０１と活性層１０４との間のｎ−半導体多層膜反射鏡(下部半導体多層膜反射鏡)１０２として、Ａｌを含まないｎ−ＧａＩｎＰとｎ−ＧａＡｓを用いたので、大きな歪みを有する活性層１０４を劣化させずに容易に成長できた。
【００９３】
なお、半導体基板１０１と活性層１０４との間の下部半導体多層膜反射鏡１０２としては、Ａｌを含まず、屈折率の大きい材料と小さい材料の組み合せを用いることができる。具体的に、ＧａＩｎＰ(低屈折率層)とＧａＡｓ(高屈折率層)の組み合せの他、ＧａＩｎＰＡｓ(低屈折率層)とＧａＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＰＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＰＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＮＡｓ(高屈折率層)等の組み合せを用いることができる。もちろん、下部半導体多層膜反射鏡の材料としてＡｌを含まない材料を用いた方が、その上に大きな歪みを有する活性層を成長することが容易であるが、Ａｌを含んだ材料を用いても成長条件を適正化することで用いることはできる。具体的に、ＡｌＡｓ(低屈折率層)とＧａＡｓ(高屈折率層)の組み合せ，ＡｌＧａＡｓとＧａＡｓ，ＡｌＡｓとＡｌＧａＡｓ，ＡｌＧａＡｓ(Ａｌ組成が大きい)とＡｌＧａＡｓ(Ａｌ組成が小さい)等の組み合せを用いることができる。
【００９４】
また、活性層１０４より表面側の上部半導体多層膜反射鏡１０９(この実施例ではｐ−半導体多層膜反射鏡)にも、Ａｌを含まず、屈折率の大きい材料と小さい材料の組み合せを用いることができる。具体的に、ＧａＩｎＰ(低屈折率層)とＧａＡｓ(高屈折率層)の組み合せの他、ＧａＩｎＰＡｓ(低屈折率層)とＧａＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＰＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＰＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＡｓ(高屈折率層)，ＧａＩｎＰ(低屈折率層)とＧａＩｎＮＡｓ(高屈折率層)等の組み合せを用いることができる。
【００９５】
但し、活性層１０４より表面側の上部半導体多層膜反射鏡１０９(この実施例ではｐ−半導体多層膜反射鏡)としてはＡｌを含んでいてもかまわない。具体的に、ＡｌＡｓ(低屈折率層)とＧａＡｓ(高屈折率層)の組み合せ，ＡｌＧａＡｓとＧａＡｓ，ＡｌＡｓとＡｌＧａＡｓ，ＡｌＧａＡｓ(Ａｌ組成が大きい)とＡｌＧａＡｓ(Ａｌ組成が小さい)等の組み合せを用いることができる。この場合、大きな歪み有する活性層１０４は、低温で成長されることから、できるだけ低温(例えば７００℃以下)で成長することが好ましい。また、上部半導体多層膜反射鏡１０９としては誘電体多層膜を用いることもできる。具体的には、ＴｉＯ₂とＳｉＯ₂の組み合せ等を用いることができる。
【００９６】
このように作製した面発光レーザ(図１０の半導体レ−ザ)の発振波長は約１．３μｍであった。また、しきい電流密度は１ｋＡ／ｃｍ²以下であった。Ｉｎ組成を３０％より大きくし、圧縮歪み量を２％以上にしたことにより、従来より窒素組成を小さくでき、しきい電流密度を劇的に低減できた。高温での特性も良好であった。また長寿命であった。
【００９７】
この実施例５では、ＭＯＣＶＤ法での成長の例を示したが、ＭＢＥ法等他の成長方法を用いることもできる。また、窒素の原料にＤＭＨｙを用いたが、活性化した窒素やＮＨ₃等他の窒素化合物を用いることもできる。
【００９８】
また、上述の例では、積層構造として３重量子井戸構造(ＴＱＷ)の例を示したが、他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)等を用いることもできる。また各層の組成厚さ等は必要に応じて他の値を設定できる。また、活性層１０４にはＧａＩｎＡｓを用いることもできる。レーザの構造も他の構造にしてもかまわない。
【００９９】
実施例６
図１１は実施例６の半導体発光素子(半導体レーザ)を示す図である。図１１に示す半導体発光素子は面発光型である。この半導体発光素子は、発光を得るための共振器を構成するため、量子井戸活性層１２３の半導体基板１２１とは反対の側には上部反射鏡１２８が形成され、また、量子井戸活性層１２３の半導体基板１２１側には下部反射鏡１２９が形成されており、上部反射鏡１２８と下部反射鏡１２９のうちの少なくとも下部反射鏡１２９は、誘電体材料による低屈折率層と高屈折率層とが交互に積層された誘電体多層膜として構成されている。この構成においても、上部反射鏡１２８，下部反射鏡１２９は、量子井戸活性層１２３からの発光に対する共振器として機能するようになっている。
【０１００】
より具体的に、図１１の半導体発光素子は、面方位(１００)のｎ−ＧａＡｓ基板１２１上に、ＧａＡｓ基板１２１に格子整合するｎ−ＧａＩｎＰＡｓクラッド層１２２(膜厚が０．５μｍ)，３層のＧａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995Ａｓ井戸層とＧａＡｓバリア層からなる多重量子井戸活性層(ＧａＩｎＮＡｓ／ＧａＡｓＱＷ活性層)１２３，ｐ−ＧａＩｎＰＡｓクラッド層１２４(膜厚が１．５μｍ)，Ａｌ_xＯ_y電流狭さく層１２５，電流注入部としてのＡｌＡｓ層１２６(膜厚が５０ｎｍ)，ｐ−ＧａＡｓコンタクト層１２７(膜厚が０．３μｍ)，ｐ−ＡｌＡｓとｐ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(２１周期)からなるｐ−半導体多層膜反射鏡(ＡｌＧａＡｓ／ＧａＡｓ上部半導体多層膜反射鏡)１２８が順次成長されている。また、図１１の半導体発光素子では、ＧａＡｓ基板１２１の一部がクラッド層１２２の表面までエッチングされ、このクラッド層１２２上にＴｉＯ₂とＳｉＯ₂の組み合わせからなる誘電体多層膜反射鏡(ＴｉＯ₂／ＳｉＯ₂下部誘電体多層膜反射鏡)１２９が形成されている。
【０１０１】
そして、電流狭さく層１２５，ｐ−ＧａＡｓコンタクト層１２７の側面には絶縁膜(ポリイミド)１３０が形成され、また、ｐ−ＧａＡｓコンタクト層１２７上には、ｐ側電極１３１が形成され、また、ＧａＡｓ基板１２１の裏面にはｎ側電極１３２が形成されている。
【０１０２】
図１１の半導体発光素子を次のように作製した。すなわち、先ず、面方位(１００)のｎ−ＧａＡｓ基板１２１上に、ＧａＡｓ基板１２１に格子整合するｎ−ＧａＩｎＰＡｓクラッド層１２２(膜厚が０．５μｍ)，３層のＧａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995Ａｓ井戸層とＧａＡｓバリア層からなる多重量子井戸活性層(ＧａＩｎＮＡｓ／ＧａＡｓ ＱＷ活性層)１２３，ｐ−ＧａＩｎＰＡｓクラッド層１２４(膜厚が１．５μｍ)，Ａｌ_xＯ_y電流狭さく層１２５，電流注入部としてのＡｌＡｓ層１２６(膜厚が５０ｎｍ)，ｐ−ＧａＡｓコンタクト層１２７(膜厚が０．３μｍ)，ｐ−ＡｌＡｓとｐ−ＧａＡｓをそれぞれの媒質内における発振波長の１／４倍の厚さで交互に積層した周期構造(２１周期)からなるｐ−半導体多層膜反射鏡(ＡｌＧａＡｓ／ＧａＡｓ上部半導体多層膜反射鏡)１２８を順次に成長させた。
【０１０３】
ここで、井戸層のＩｎ組成ｘは４０％，窒素組成は０．５％とした。また、井戸層の厚さは７ｎｍとした。圧縮歪量は約２．７％であった。成長方法はＭＯＣＶＤ法で行なった。原料にはＴＭＧ(トリメチルガリウム)，ＴＭＩ(トリメチルインジウム)，ＡｓＨ₃(アルシン)，ＰＨ₃(フォスフィン)，そして窒素の原料にはＤＭＨｙ(ジメチルヒドラジン)を用いた。なお、Ａｌを含んだｐ−半導体多層膜反射鏡１２８は、活性層１２３への影響の小さい低温の６８０℃で成長した。
【０１０４】
そして、フォトリソグラフィ−とエッチング工程によりｐ−半導体多層膜反射鏡１２８の上部まで直径１０μｍの円形にメサエッチングし、更に直径３０μｍの円形にｐ−ＧａＡｓコンタクト層１２７をメサエッチングした。そして、絶縁膜(ポリイミド)１３０をコートして電流注入部１２６を開けて、ｐ側電極１３１を形成した。そして、半導体基板１２１をｎ−ＧａＩｎＰＡｓクラッド層１２２の表面が現れるまでエッチングし、ＴｉＯ₂とＳｉＯ₂の組み合せからなる誘電体多層膜反射鏡１２９を形成した。更に、基板１２１の裏面には、ｎ側電極１３２を形成した。このような構造では、光取り出し部は、基板１２１の裏面となる。
【０１０５】
この実施例６では、半導体基板１２１と大きな歪みを有する活性層１２３との間に半導体多層膜反射鏡を挿入せず、基板１２１側の反射鏡として誘電体多層膜を用いることで、大きな歪みを有する活性層１２３を劣化させずに容易に成長できた。
【０１０６】
換言すれば、半導体基板側の反射鏡を半導体部の外部に形成し、半導体基板と大きい歪みを有する量子井戸活性層との間にＡｌを含む半導体層を形成していないので、量子井戸活性層成長時のエピ基板表面の状態は良好であり、大きい歪みの量子井戸層を容易に良好に成長できた。
【０１０７】
このようにして作製した面発光レーザの発振波長は約１．３μｍであった。また、しきい電流密度は１ｋＡ／ｃｍ²以下であった。Ｉｎ組成を３０％より大きくし、圧縮歪み量を２％以上にしたことにより、従来より窒素組成を小さくでき、しきい電流密度を劇的に低減できた。高温での特性も良好であった。
【０１０８】
この実施例６では、ＭＯＣＶＤ法での成長の例を示したが、ＭＢＥ法等他の成長方法を用いることもできる。また、窒素の原料にＤＭＨｙを用いたが、活性化した窒素やＮＨ₃等他の窒素化合物を用いることもできる。
【０１０９】
また、上述の例では、積層構造として３重量子井戸構造(ＴＱＷ)の例を示したが他の井戸数の量子井戸を用いた構造(ＳＱＷ，ＭＱＷ)等を用いることもできる。また各層の組成厚さ等は必要に応じて他の値を設定できる。また、活性層１２３にはＧａＩｎＡｓを用いることもできる。レーザの構造も他の構造にしてもかまわない。
【０１１０】
このような大きな歪みを有した活性層の品質は、構造，成長条件に非常に敏感であり、本発明はこれに絞って述べたが、もちろん本発明の構造，成長条件等は、活性層歪みが２％より小さくても効果があるものである。
【０１１１】
上述の各実施例では、半導体基板にＧａＡｓ基板が用いられている場合、ＧａＡｓ基板上の半導体材料としてＧａＩｎＡｓ，ＧａＩｎＮＡｓを用いるときの例を示したが、このほかにも、半導体基板にＧａＡｓ基板を用いる場合に、ＧａＡｓ基板上の半導体材料としてＧａＩｎＰ，ＧａＰＡｓを用いるとき、また半導体基板にＩｎＰ基板が用いられる場合に、ＩｎＰ基板上の半導体材料としてＧａＩｎＡｓ，ＧａＩｎＰＡｓ，ＩｎＰＡｓ，ＩｎＮＰＡｓなどを用いるときなどにも、本発明を適用できる。すなわち、本発明は、半導体基板と格子定数の大きく異なる半導体を用いた半導体発光素子に有効となる。また、本発明は、他の発光素子，受光素子または電子素子等のIII−Ｖ族混晶半導体を用いた半導体素子にも適用できる。
【０１１２】
【発明の効果】
以上に説明したように、請求項１記載の発明によれば、半導体基板上に、歪み量が２％を越える歪み量子井戸層を含む活性層と、光とキャリアを閉じ込めるクラッド層とを有し、 III −Ｖ族半導体で形成された半導体発光素子の製造方法であって、 III 族原料として有機金属化合物を用いた有機金属気相成長法により前記半導体発光素子を形成するようにしており、前記歪み量子井戸層をＧａ _x Ｉｎ _1-x Ｎ _y Ａｓ _1-y ( ０≦ｘ≦１，０＜ｙ＜１ ) で形成する場合、Ｎの原料として、ＤＭＨｙ ( ジメチルヒドラジン ) ，ＭＭＨｙ ( モノメチルヒドラジン ) 等の有機系窒素化合物を用いて前記歪み量子井戸層を６００℃以下の温度で成長させ、前記活性層を成長させた後、前記クラッド層を７００℃以下の温度で成長させる。ここで、有機金属気相成長法は、過飽和度が高い成長方法であり、高歪みの量子井戸層や窒素をＶ族に含んだＧａＩｎＮＡｓのような材料の成長手段として有効である。また、請求項１記載の発明によれば、、歪み量子井戸層は、Ｇａ _x Ｉｎ _1-x Ｎ _y Ａｓ _1-y ( ０≦ｘ≦１，０≦ｙ＜１ ) で形成する場合、Ｎの原料として、ＤＭＨｙ ( ジメチルヒドラジン ) ，ＭＭＨｙ ( モノメチルヒドラジン ) 等の有機系窒素化合物を用いて形成する。すなわち、有機系窒素化合物は低温で分解するので、６００℃以下のような低温成長に適している。また、本発明のように特に歪みの大きい量子井戸層を成長する場合は、例えば、５００℃〜６００℃程度の低温成長が好ましく、この観点からも低温で分解する有機系窒素化合物は好ましい。すなわち、低温では歪み量子井戸層の臨界膜厚が厚くなるので、特に２％を超えるような高歪み量子井戸層の成長には、６００℃以下の低温成長が適している。また、請求項１記載の発明によれば、前記活性層を成長させた後、前記クラッド層を７００℃以下の温度で成長するので、ＡｌＧａＡｓを使用できる。
【図面の簡単な説明】
【図１】本発明に係る半導体発光素子の構成例を示す図である。
【図２】図１の半導体発光素子の活性層の一例を示す図である。
【図３】面方位が(１００)であるＧａＡｓ基板上に形成された半導体発光素子のＰＬ特性と、面方位が(１００)から〔０１１〕方向に１５゜の角度で傾いているＧａＡｓ基板上に形成された半導体発光素子のＰＬ特性とを示す図である。
【図４】実施例１の半導体発光素子を示す図である。
【図５】図４の半導体発光素子の発振波長に対するしきい電流密度を示す図である。
【図６】実施例２の半導体発光素子を示す図である。
【図７】図６の半導体発光素子の連続動作における電流−電圧特性を示す図である。
【図８】実施例３の半導体発光素子を示す図である。
【図９】実施例４の半導体発光素子を示す図である。
【図１０】実施例５の半導体発光素子を示す図である。
【図１１】実施例６の半導体発光素子を示す図である。
【図１２】４つの試料ａ，ｂ，ｃ，ｄのＰＬ特性を示す図である。
【図１３】ガイド層としてＧａＩｎＰを用いた試料とＡｌＧａＡｓを用いた試料のＰＬ特性を示す図である。
【図１４】一般に支持されているＭａｔｔｈｅｗｓ ａｎｄ Ｂｌａｋｅｓｌｅｅの理論に基づいて計算したＧａＡｓ基板上のＧａＩｎＡｓ層の臨界膜厚を示す図である。
【図１５】ＧａＩｎＡｓ単一量子井戸層からのＰＬ中心波長とＰＬ強度との関係を示す図である。
【符号の説明】
１ 半導体基板
３ 活性層
２ 歪み量子井戸層
４ クラッド層
５ バリア層
２１ ｎ−ＧａＡｓ基板
２２ ｎ−ＧａＡｓバッファ層
２３ ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層
２４ ＧａＡｓ光ガイド層
２５ａ，２５ｂ Ｇａ_1-xＩｎ_xＡｓ量子井戸層
２６ ＧａＡｓバリア層
２７ 活性層(発光層)
２８ ＧａＡｓ光ガイド層
２９ ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層
３０ ｐ−ＧａＡｓコンタクト層
３２ ｐ側電極
３１ 絶縁膜
３３ ｎ側電極
４１ ｎ−ＧａＡｓ基板
４２ ｎ−ＧａＡｓバッファ層
４３ ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層
４４ ＧａＡｓ光ガイド層
４５ａ，４５ｂ Ｇａ_0.67Ｉｎ_0.33Ｎ_0.006Ａｓ_0.994量子井戸層
４６ ＧａＡｓバリア層
４７ 活性層(発光層)
４８ ＧａＡｓ光ガイド層
４９ ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層
５０ ｐ−ＧａＡｓコンタクト層
５２ ｐ側電極
５１ 絶縁膜
５３ ｎ側電極
６１ ｎ−ＧａＡｓ基板
６２ ｎ−ＧａＡｓバッファ層
６３ ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層
６４ ＧａＡｓ光ガイド層
６５ａ，６５ｂ Ｇａ_0.6Ｉｎ_0.4Ｎ_0.005Ａｓ_0.995量子井戸層
６６ ＧａＡｓバリア層
６７ 活性層(発光層)
６８ ＧａＡｓ光ガイド層
６９ ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層
７０ ｐ−ＧａＡｓコンタクト層
７２ ｐ側電極
７１ 絶縁膜
７３ ｎ側電極
８１ ｎ−ＧａＡｓ基板
８２ ｎ−ＧａＡｓバッファ層
８３ ｎ−ＧａＩｎＰ(Ａｓ)下部クラッド層
８４ ＧａＡｓ光ガイド層
８５ａ，８５ｂ Ｇａ_0.65Ｉｎ_0.35Ｎ_0.007Ａｓ_0.993量子井戸層
８６ａ，８６ｂ，８６ｃ ＧａＡｓバリア層
８７ 活性層(発光層)
８８ ＧａＡｓ光ガイド層
８９ ｐ−ＧａＩｎＰ(Ａｓ)上部クラッド層
９０ ｐ−ＧａＡｓコンタクト層
９２ ｐ側電極
９１ 絶縁膜
９３ ｎ側電極
１０１ ＧａＡｓ基板
１０２ 下部半導体多層膜反射鏡
１０３ ＧａＡｓスペ−サ層
１０４ 活性層
１０５ ＧａＡｓスペ−サ層
１０６ 電流狭さく層
１０７ 電流注入層
１０８ ｐ−ＧａＡｓコンタクト層
１０９ 上部半導体多層膜反射鏡
１１０ 絶縁膜
１１１ ｐ側電極
１１２ ｎ側電極
１２１ ＧａＡｓ基板
１２２ ＧａＩｎＰＡｓクラッド層
１２３ 活性層
１２４ ＧａＩｎＰＡｓクラッド層
１２５ 電流狭さく層
１２６ 電流注入部
１２７ ｐ−ＧａＡｓコンタクト層
１２８ 上部半導体多層膜反射鏡
１２９ 下部誘電体多層膜反射鏡
１３０ 絶縁膜
１３１ ｐ側電極
１３２ ｎ側電極[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a semiconductor light emitting device used for a semiconductor light emitting device for optical communication, a light emitting diode, a photodiode for infrared light, and the like.Of childIt relates to a manufacturing method.
[0002]
[Prior art]
Conventionally, an optical communication system using an optical fiber is mainly used in a trunk system, but in the future, it is considered to be used in a subscriber system including each home. In order to realize this, it is necessary to reduce the size and cost of the system, and it is necessary to realize a system that does not require a Peltier element for temperature control of a semiconductor light emitting element used for optical communication.
[0003]
In order to realize such an optical communication system, a semiconductor light emitting device used for optical communication is desired to have a high characteristic temperature element with low threshold operation and little characteristic change due to temperature change. In general, when a material having a lattice constant different from that of a semiconductor substrate is formed on a semiconductor substrate, a thickness up to a critical film thickness estimated from a strain associated with the difference in lattice constant can be formed. However, in the conventional GaInPAs / InP-based materials, there is no material that can increase the band discontinuity of the conduction band, and it has been difficult to achieve a high characteristic temperature.
[0004]
In order to improve this, for example, Japanese Patent Application Laid-Open No. 6-275914 proposes a semiconductor light emitting device in which an active layer is formed on a ternary substrate made of GaInAs. In this semiconductor light emitting device, since GaInAs is used for the substrate, a wide gap material can be formed on the GaInAs substrate, so that it is possible to obtain band discontinuity of a large conduction band that could not be realized on the InP substrate. .
[0005]
Attempts have also been made to form long wavelength lasers on GaAs substrates. Japanese Patent Laid-Open No. 7-193327 proposes a semiconductor laser device in which a GaInAs lattice relaxation buffer layer having a lattice constant larger than that of GaAs is formed on a GaAs substrate and an active layer is formed thereon. In this semiconductor laser device, since a material having a lattice constant larger than that of GaAs can be formed on the GaInAs lattice relaxation buffer layer, similarly to the semiconductor light emitting device proposed in Japanese Patent Laid-Open No. 6-275914, a large conduction band is obtained. Band discontinuities can be obtained.
[0006]
Further, a material having a wider gap than that formed on the InP substrate or the GaInAs ternary substrate can be formed on the GaAs substrate. However, conventionally, there has been no band gap active layer material corresponding to a long wavelength such as a 1.3 μm band. That is, when GaInAs is formed on a GaAs substrate, GaInAs increases in wavelength with an increase in In composition, but with an increase in strain. Since the limit strain is about 2%, the wavelength of 1.1 μm is said to be the limit (document “IEEE Photonics. Technol. Lett. Vol.9 (1997) pp.1319-1321”). .
[0007]
Therefore, as another method, Japanese Patent Laid-Open No. 6-37355 proposes forming a GaInNAs-based material on a GaAs substrate. GaInNAs is a group III-V mixed crystal semiconductor containing N and other group V elements. When a GaInNAs material is formed on a GaAs substrate, it is possible to lattice-match the lattice constant to GaAs by adding N to GaInAs, which has a larger lattice constant than GaAs. The band gap energy is reduced due to the fact that the band gap energy is small compared to the above, and light emission in the 1.3 μm and 1.5 μm bands becomes possible. In the document “Jpn.J.Appl.Phys.Vol.35 (1996) pp.1273-1275”, the band lineup is calculated by Kondo et al. When a GaInNAs material is formed on a GaAs substrate, a GaAs lattice matching system is used as described above, so that wide gap AlGaAs can be used for the cladding layer. In addition, the addition of N reduces the band gap and decreases the energy levels of the conduction band and valence band, thereby increasing the band discontinuity of the conduction band at the heterojunction. For this reason, it is expected that a high characteristic temperature semiconductor light emitting device can be realized.
[0008]
Regarding the structure of the GaInNAs laser, the edge-emitting type has been proposed in Japanese Patent Laid-Open Nos. 8-195522 and 10-12604, and the surface-emitting type has been proposed in Japanese Patent Laid-Open Nos. 9-237942 and 10-10. No. 74979 has been proposed. In recent years, a 1.3 μm-GaInNAs laser on a GaAs substrate has been actually realized. That is, a double hetero structure having a thick GaInNAs having a nitrogen composition of 3% and an In composition of 10% lattice-matched on the GaAs substrate as an active layer (document "Elecron. Lett. Vol.33 (1997) pp.1386-1387") In addition, a compression-strained single quantum well structure using GaInNAs having a nitrogen composition of 1% and an In composition of 30% (document “IEEE Photonics. Technol. Lett. Vol.10 (1998) pp.487-488”) has been proposed. Yes.
[0009]
[Problems to be solved by the invention]
However, a ternary substrate made of GaInAs proposed in Japanese Patent Laid-Open No. 6-275914 is difficult to produce. Further, the structure in which the GaInAs lattice relaxation buffer layer proposed in Japanese Patent Laid-Open No. 7-193327 is basically a lattice mismatch system with respect to the substrate, and thus there is a problem in terms of lifetime. In addition, a group III-V mixed crystal semiconductor containing nitrogen and other group V elements such as GaInNAs has a problem that the crystallinity is greatly deteriorated as the nitrogen composition is increased.
[0010]
  The present invention provides a high-performance long-wavelength semiconductor light-emitting element in which deterioration of crystallinity is prevented.Of childThe object is to provide a manufacturing method.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, an invention according to claim 1 has an active layer including a strained quantum well layer having a strain amount exceeding 2% on a semiconductor substrate, and a cladding layer for confining light and carriers.And III -V group semiconductor formedManufacturing method of semiconductor light emitting deviceBecause III The semiconductor light emitting device is formed by metal organic vapor phase epitaxy using an organometallic compound as a group source material, and the strained quantum well layer is formed of Ga. _x In _1-x N _y As _1-y ( 0 ≦ x ≦ 1, 0 <y <1 ) As a raw material for N, DMHy ( Dimethylhydrazine ) , MMHy ( Monomethylhydrazine ) Using organic nitrogen compounds such asThe strained quantum well layerTheGrowth at temperatures below 600 ° CAnd growing the active layer, and then growing the cladding layer at a temperature of 700 ° C. or lower.It is characterized by that.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a semiconductor light emitting device according to the present invention. In the semiconductor light emitting device (semiconductor laser) shown in FIG. 1, an active layer 3 including a strained quantum well layer (light emitting layer) 2 and a clad layer 4 for confining light and carriers are formed on a semiconductor substrate 1. The strain amount of the strained quantum well layer 2 with respect to the substrate 1 and the clad layer 4 is greater than 2%.
[0028]
Here, GaAs is used for the semiconductor substrate 1. Further, GaInP or GaInPAs is used as the cladding layer 4. Further, the semiconductor light emitting device (semiconductor laser) of FIG. 1 is a surface emitting type.
[0029]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG._xIn_1-xN_yAs_1-y(0 ≦ x ≦ 1, 0 ≦ y <1). And Ga which is the strain quantum well layer 2_xIn_1-xN_yAs_1-yRegarding (0 ≦ x ≦ 1, 0 ≦ y <1), the composition wavelength of GaInAs when not containing nitrogen is longer than 1.12 μm. More specifically, the composition of In in the group III element of the strained quantum well layer 2 is greater than 30%. Further, the nitrogen composition in the group V element of the strained quantum well layer 2 is in the range of 0 to 1%.
[0030]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the plane orientation of the semiconductor substrate 1 is within a range of an inclination angle of 5 ° from (100).
[0031]
In the semiconductor light emitting device (semiconductor laser) shown in FIG. 1, a barrier layer for compensating stress is formed in the active layer 3 in the vicinity of the strained quantum well layer 2. FIG. 2 is a diagram showing an example of an active layer in which a barrier layer is formed. In the example of FIG. 2, the active layer 3 includes well layers 2a and 2b, well layers 2a and 2b, and well layers 2a. GaNPAs barrier layers 5a, 5b, and 5c provided below and well layer 2b are formed.
[0032]
In the present invention, in a semiconductor light emitting device (semiconductor laser) in which an active layer 3 including a strained quantum well layer 2 and a clad layer 4 for confining light and carriers are formed on a semiconductor substrate 1, the semiconductor substrate 1 and the clad The strain amount of the strain quantum well layer 2 with respect to the layer 4 is greater than 2%, and a semiconductor light emitting device (semiconductor laser) having a wavelength that cannot be obtained conventionally is obtained by crystal growth of a material composition that cannot be obtained conventionally. Can do.
[0033]
Further, since the semiconductor substrate 1 is a GaAs substrate, a wide gap material such as AlGaAs, AlAs, GaInP, and AlInP that cannot be grown thickly on the InP substrate can be grown as a cladding layer of the semiconductor light emitting device, and a long wavelength band can be obtained. It is extremely excellent as a substrate for semiconductor light emitting devices (semiconductor lasers).
[0034]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG._xIn_1-xN_yAs_1-y(0 ≦ x ≦ 1, 0 ≦ y <1). Therefore, in the case of GaInAs with y = 0, the wavelength up to about 1.2 μm, and in the case of GaInNAs, the 1.3 μm band or the like depending on the In composition and the nitrogen composition. The light emitting layer of a longer wavelength semiconductor light emitting device (semiconductor laser) can be formed.
[0035]
In addition, Ga which is a strained quantum well layer_xIn_1-xN_yAs_1-yWith regard to (0 ≦ x ≦ 1, 0 ≦ y <1), the PL (Photo luminescence) wavelength of GaInAs when not containing nitrogen is longer than 1.12 μm. Crystal growth of a material having a composition wavelength that could not be used for the light emitting layer of the light emitting element (semiconductor laser) can increase the degree of freedom in designing the structure of the semiconductor light emitting element (semiconductor laser). Specifically, in GaInAs with y = 0, by setting the In composition to 30% or more, a semiconductor light emitting device (semiconductor laser) having a wavelength longer than the conventional limit of 1.1 μm can be obtained. By setting the composition to 30% or more, the composition of nitrogen can be reduced as compared with the prior art. For example, in the case of obtaining a 1.3 μm band, the nitrogen composition can be made 1% or less.
[0036]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the nitrogen composition in the group V element of the strained quantum well layer 2 is in the range of 0 to 1%, and the nitrogen composition is in the small range of 0 to 1%. If this is the case, the decrease in crystallinity can be suppressed, so that a high-performance long wavelength band semiconductor light emitting device (semiconductor laser) can be obtained.
[0037]
In the semiconductor light emitting device (semiconductor laser) of FIG. 1, the plane orientation of the semiconductor substrate 1 is within a range of an inclination angle of 5 ° from (100), and the plane orientation of the semiconductor substrate is greatly tilted from (100). (For example, it is more inclined in the [011] direction), it is easier to increase the In composition of GaInNAs and GaInAs in the strained quantum well in the vicinity of (100), and it is suitable for longer wavelengths, and further improves the luminous efficiency. Since it is easy to make it high, it is suitable for a substrate of a highly strained quantum well semiconductor light emitting device (semiconductor laser).
[0038]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, GaInP or GaInPAs is used as the cladding layer 4, and GaInP or GaInAs not containing Al can obtain a good crystal at a lower growth temperature than AlGaAs. Therefore, it is preferable in the case of manufacturing a high strain quantum well laser in which low temperature growth is preferable, and it is easy to obtain a high strain quantum well layer having good crystallinity.
[0039]
In addition, when the semiconductor light emitting device (semiconductor laser) of FIG. 1 is a surface emitting type, a long wavelength band semiconductor light emitting device (semiconductor laser) can be formed on a GaAs substrate and has a large refractive index difference. Since a GaAs multilayer mirror can be used, a thin thickness is sufficient, and AlAs is oxidized by AlAs._xO_yCan be used for narrowing the current, and is extremely effective as compared with a long-wavelength surface emitting semiconductor light emitting device (semiconductor laser) on a conventional InP substrate.
[0040]
Further, in the semiconductor light emitting device (semiconductor laser) of FIG. 1, the active layer 3 has a barrier layer (well layer strain compensated for stress) in the vicinity of the strained quantum well layers 2a and 2b, as shown in FIG. The strain compensation layers 5a, 5b, and 5c are formed. If there is a strain compensation layer that relaxes strain in the well layer, the quality of the well layer can be improved and the number of well layers can be increased. The design range of the semiconductor light emitting device (semiconductor laser) can be increased, and it is effective to have an optimum structure for high performance.
[0041]
In a method for manufacturing a semiconductor light emitting device (semiconductor laser) having an active layer 3 including a strained quantum well layer 2 and a clad layer 4 that confines light and carriers on a semiconductor substrate 1, the strained quantum well layer 2 is formed at a low temperature. In particular, low temperature growth at a temperature of 600 ° C. or lower is suitable for the growth of a high strain quantum well layer in which the strain amount exceeds 2%.
[0042]
In the case of a semiconductor light emitting device (semiconductor laser) formed of a III-V group semiconductor, the semiconductor light emitting device is formed by a metal organic vapor phase growth method using an organometallic compound as a group III material. That is, the metal organic vapor phase growth method is a growth method having a high degree of supersaturation, and is effective for growing a high strained quantum well layer or a material such as GaInNAs containing nitrogen in the V group.
[0043]
Further, the strain quantum well layer 2 is made of Ga_xIn_1-xN_yAs_1-yIn the case of forming with (0 ≦ x ≦ 1, 0 ≦ y <1), an organic nitrogen compound such as DMHy (dimethylhydrazine) or MMHy (monomethylhydrazine) is used as a raw material for N. That is, since organic nitrogen compounds decompose at low temperatures, they are suitable for low temperature growth at 600 ° C. or lower. Further, when a quantum well layer having a particularly large strain is grown as in the present invention, for example, low temperature growth of about 500 ° C. to 600 ° C. is preferable, and an organic nitrogen compound that decomposes at a low temperature is also preferable from this viewpoint.
[0044]
As described above, GaInAs on a GaAs substrate can increase the oscillation wavelength of a semiconductor light emitting device (semiconductor laser) by increasing the In composition, but it also increases the amount of distortion. The limit distortion is about 2%, and the oscillation wavelength is said to be 1.1 μm (refer to the document “IEEE Photonics. Technol. Lett. Vol.9 (1997) pp.1319-1321”). ).
[0045]
When a material having a different lattice constant is grown on the underlying substrate, the lattice elastically deforms and absorbs its energy. However, when a material having a different lattice constant is grown thicker than the underlying substrate, the strain energy cannot be absorbed only by elastic deformation, and misfit dislocation occurs. This film thickness is called critical film thickness. If misfit dislocations occur, it is difficult to produce a good device.
[0046]
Theoretically, the critical film thickness (h_c) Is given by Matthews and Blakeslee (reference “J. Crystal Growth. 27 (1974) 118.”) by the following equation:
[0047]
[Expression 1]

[0048]
Where ν is Poisson's ratio (ν = C₁₂/ (C₁₁+ C₁₂; C₁₁, C₁₂Is the elastic stiffness constant), α is the angle between the Burgers vector at the interface and the line segment of the dislocation line (cos α = 1/2), and λ is in the interface perpendicular to the intersecting line between the sliding surface and the interface Angle formed by direction and Burgers vector (cos λ = 1/2), b = a / 2^1/2    (A: lattice constant), f is the degree of lattice mismatch (f = Δa / a). Equation 1 is an equation for growing a single layer film on an infinitely thick substrate. Hereinafter, the critical film thickness h given by this equation (Equation 1)._cIs referred to as the critical film thickness based on the theory of Matthesands Blakeslee.
[0049]
FIG. 14 shows the critical film thickness of the GaInAs layer on the GaAs substrate calculated based on the generally supported Matthews and Blakeslee theory. Ga_1-xIn_xGa with nitrogen added to As_1-xIn_xThe lattice constant of NAs is such that Ga is 3% smaller in In composition x per 1% of nitrogen addition._1-yIn_yThe lattice constant is almost the same as As (y = x−0.03).
[0050]
When GaInAs is formed on a GaAs substrate, the amount of strain increases as the In composition increases, so that the critical film thickness, which is a film that can be grown two-dimensionally on a plane, becomes thinner.
[0051]
On the other hand, the inventors of the present application can grow the strain amount of the quantum well layer with respect to the GaAs substrate by 2% or more by setting the In composition to a value exceeding 30% in the GaInAs quantum well layer on the GaAs substrate. It has been found that a semiconductor light emitting device (semiconductor laser) having a wavelength longer than 1.1 μm, which has been considered the limit, can be realized. Further, in the strained quantum well layer 2, a substantial critical film thickness h is obtained by growth under non-equilibrium conditions such as low temperature growth._c'Is the critical thickness h of Matthews and Blakeslee._cIt has been found that a semiconductor light emitting device (semiconductor laser) with a long wavelength exceeding 1.2 μm can be realized.
[0052]
That is, the inventor of the present application provides a semiconductor light emitting device in which an active layer including a strained quantum well layer and a cladding layer for confining light and carriers are formed on a semiconductor substrate. The thickness of the well layer is a critical thickness h based on the theory of Matthews and Blakeslee._cIt has been found that when it is thicker, it is possible to obtain a semiconductor light emitting device such as a semiconductor laser having a wavelength that cannot be obtained conventionally, and it is also possible to obtain a higher performance electronic device such as HEMT (high electron mobility transister). .
[0053]
FIG. 14 shows an experimental example. Referring to FIG. 14, for example, when the In composition is 32% and the thickness is 8.6 nm, the PL center wavelength is 1.13 μm, and when the In composition is 36% and the thickness is 7.8 nm, the PL center wavelength is When the In composition was 39% and the thickness was 7.2 nm, the PL center wavelength was 1.2 μm. These are the critical film thicknesses h calculated based on Matthews and Blakeslee's theory (Equation 1)._cThe thickness exceeds.
[0054]
FIG. 15 shows the relationship between the PL center wavelength and the PL intensity from the GaInAs single quantum well layer. The In composition x of the GaInAs well layer (solid line portion in the figure) was 31% to 42%. The thickness of each well layer 25a, 25b was reduced to about 9 nm to about 6 nm in accordance with the increase of the In composition x. A quantum well layer having a strong PL intensity up to a wavelength of about 1.2 μm was obtained. It can be seen that the PL intensity gradually decreases up to a wavelength of 1.2 μm, whereas the PL intensity rapidly decreases beyond 1.2 μm. This also corresponds to the surface property, and was a mirror surface up to 1.2 μm. From these results, the sudden drop in the PL intensity indicates that the quantum well layer thickness is substantially equal to the critical film thickness h._cIt is thought that it was over '. In general, it has been reported that the critical film thickness obtained experimentally increases in MOCVD or MBE under strong non-equilibrium growth conditions such as low temperature growth and high growth rate. It has also been reported that, depending on the growth conditions (for example, high-temperature growth), three-dimensional growth and surface roughness occur even when the thickness is less than the critical thickness based on theory. Therefore, this result is the critical film thickness h based on the theory._cSubstantially critical film thickness h by growth under non-equilibrium conditions such as lower temperature growth_cSince ′ is thicker, it is considered that a thicker film could be grown two-dimensionally without causing misfit dislocations.
[0055]
Furthermore, the inventors of the present application have found that, in the case of a GaInNAs laser, since the nitrogen composition can be reduced by increasing the In composition x as described above, the characteristics of the GaInNAs laser can be greatly improved.
[0056]
In addition, it has been found that when using laser, GaInP (As) can be formed more easily than using AlGaAs as the cladding layer. The reason is as follows.
[0057]
That is, a GaInNAs or GaInAs active layer having a large strain can be grown at a low temperature (for example, 600 ° C. or less). However, the growth temperature of AlGaAs is generally high (eg, 700 ° C. or higher). The inventor of the present application conducted a heat treatment experiment on the assumption that an AlGaAs cladding layer is grown on the active layer after the active layer is grown. Specifically, four samples were sequentially grown on a (100) GaAs substrate with a GaAs layer (film thickness 0.2 μm), a GaInNAs well layer (film thickness 7 nm), and a GaAs layer (film thickness 50 nm). Samples (a, b, c, d) were prepared. The four samples a, b, c, and d have the same In composition and different nitrogen compositions. That is, the nitrogen (N) composition of sample a is 0.2%, the nitrogen (N) composition of sample b is 0.2%, and the nitrogen (N) composition of sample c is 0.5%, Sample d has a nitrogen (N) composition of 0.8%. Then, using the MOCVD growth apparatus, AsH_ThreeIn an atmosphere, samples c and d were heat-treated (annealed) at a temperature of 680 ° C., sample b at a temperature of 700 ° C., and sample a at a temperature of 780 ° C. for 30 minutes. FIG. 12 shows the PL characteristics of these samples a, b, c, and d. In FIG. 12, the dotted line is the spectrum before the heat treatment, and the solid line is the spectrum after the heat treatment. It can be seen that the peak wavelength is shifted to the short wavelength side by the heat treatment, and the shift amount is larger as the heat treatment temperature is higher. At the same temperature, the shift amount is the same between samples with different amounts of nitrogen (sample c and sample d), and the cause of this shift is considered to be the diffusion of In. It can also be seen that the emission intensity decreases at 780 ° C. and increases at 700 ° C. or lower. The cause of the increase in emission intensity is considered to be a decrease in defects in the active layer due to heat treatment, and the cause of the decrease is considered to be deterioration of crystallinity.
[0058]
It has been found that when a GaInNAs or GaInAs active layer having such a large strain is grown, an upper layer (for example, a clad layer) is grown at a high temperature such as 780 ° C. For this reason, GaInP (As), which can be favorably grown at a low temperature, is preferable as the upper cladding layer. However, AlGaAs can be used because there is no major problem if it is grown at a temperature of 700 ° C. or lower.
[0059]
Another reason is that if the AlGaAs is grown before the GaInNAs or GaInAs active layer having a large strain is grown, the quality of the active layer is easily deteriorated. The inventor of the present application has a guide layer (film thickness of 0.2 μm), a GaAs layer (film thickness of 100 nm), a GaInNAs well layer (film thickness of 7 nm), a GaAs layer (film thickness of 100 nm) and a guide layer (film thickness of 50 nm) were sequentially grown to prepare two samples. The first sample is Ga as a guide layer (cladding layer)._0.5In_0.5P is used (hereinafter referred to as a sample using GaInP), and the second sample is made of Al as a guide layer (cladding layer)._0.4Ga_0.6As was used (hereinafter referred to as a sample using AlGaAs). A sample using GaInP has a larger In composition and a larger strain. FIG. 13 shows the PL characteristics of the first sample (GaInP) and the second sample (AlGaAs). From FIG. 13, it can be seen that the sample using GaInP has a larger distortion than the sample using AlGaAs, although the distortion is longer and the wavelength is longer and the growth is difficult.
[0060]
As a cause of this, it is considered that defects caused by Al appear on the growth surface during growth, always propagate to the growth surface, reach the GaInNAs well layer, and deteriorate the well layer. In other words, it was found that the epitaxial substrate surface just before the growth of the quantum well active layer cannot be grown with high quality unless the surface state is good. For this reason, when AlGaAs is used as the lower cladding layer, it is necessary to devise a means to stop this defect before the well layer growth. When GaInP (As) containing no Al is used as the cladding layer between the semiconductor substrate and the active layer, the state of the epi-substrate surface immediately before the growth of the quantum well active layer is good, and a large strained quantum well layer can be easily formed. Can grow well. As described above, it is understood that GaInP (As) is preferably used as the cladding layer, particularly as the lower cladding layer between the semiconductor substrate and the active layer having a large strain.
[0061]
Furthermore, the inventor of the present application indicates that the plane orientation of the GaAs substrate is more in the vicinity of (100) than in the case where the plane orientation is greatly inclined from (100) (for example, it is greatly inclined in the [011] direction from (100)). It has been found that the In composition is easily increased and the light emission efficiency is easily increased. One method for obtaining high-quality GaInNAs at a long wavelength such as the 1.3 μm band used in optical communication is to increase the In composition to increase the wavelength and reduce the nitrogen composition in GaInNAs. In each of the case where the plane orientation of the GaAs substrate is (100) and the case where the plane orientation of the substrate is inclined at an angle of 15 ° from the (100) direction to the [011] direction, Ga is formed on the GaAs substrate._0.5In_0.5An active layer comprising a P layer (with a thickness of 0.2 μm), a GaAs layer (with a thickness of 100 nm), a GaInNAs quantum well layer (light emitting layer) (with a thickness of 7 nm), and a GaAs barrier layer (with a thickness of 13 nm) A GaAs layer (film thickness is 100 nm), Ga_0.5In_0.5A P layer (with a film thickness of 50 nm) and a GaAs layer (with a film thickness of 50 nm) were sequentially formed. FIG. 3 shows a PL characteristic (indicated by reference symbol A) of a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100) and an angle of 15 ° from the (100) to the [011] direction. 2 shows PL characteristics (indicated by symbol B) of a semiconductor light emitting device formed on a GaAs substrate tilted by. Note that in a semiconductor light emitting device formed on a GaAs substrate whose plane orientation is inclined at an angle of 15 ° from the (100) direction to the [011] direction, nitrogen is added to GaInAs having a PL wavelength of 1.06 μm. On the other hand, in a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100), nitrogen is added to GaInAs having a PL wavelength of 1.13 μm.
[0062]
As can be seen from FIG. 3, the semiconductor light emitting device formed on the GaAs substrate having the plane orientation of (100) has a higher light emission intensity despite the longer wavelength and is more suitable. In contrast, in a semiconductor light emitting device formed on a GaAs substrate whose plane orientation is inclined at an angle of 15 ° from the (100) direction to the [011] direction, the In composition is increased and the wavelength is longer than the wavelength of 1.06 μm. However, it was difficult to increase the In composition. On the other hand, in a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100), strong light emission was observed up to a wavelength of about 1.2 μm using GaInAs. For this reason, it is preferable that the inclination angle of the plane orientation of the GaAs substrate from (100) is within a range of 5 °.
[0063]
【Example】
Next, examples will be described.
Example 1
4 is a diagram showing a semiconductor light emitting device of Example 1. FIG. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 4 has an SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 4 has an n-GaAs buffer layer 22 and an n-GaInP (As) lower cladding layer 23 (with a film thickness of 1.. 5 μm), GaAs light guide layer 24 (film thickness is 100 nm), Ga_1-xIn_xAn active layer (light emitting layer) 27 composed of As well layers 25a and 25b and a GaAs barrier layer 26 (thickness 13 nm), a GaAs light guide layer 28 (thickness 100 nm), and a p-GaInP (As) upper cladding layer 29 (film thickness is 1.5 μm) and p-GaAs contact layer 30 (film thickness is 0.3 μm) are sequentially formed. Further, in the semiconductor light emitting device of FIG. 4, the GaAs contact layer 30 is removed by etching except for the current injection portion, and the p-side electrode 32 is formed through the insulating film 31 from which the portion to be the current injection portion is removed. An n-side electrode 33 is formed on the back surface of the substrate 21.
[0064]
Where Ga_1-xIn_xThe In composition x of the As well layers 25a and 25b was 31% to 42%. The thickness of each well layer 25a, 25b was reduced to about 9 nm to about 6 nm in accordance with the increase in In composition. The quantum well layer thickness of these lasers is the critical film thickness h based on the theory of Matthews and Blakeslee._cIt is a thicker condition. For example, when the In composition is 32% and the thickness is 8.6 nm, the oscillation wavelength is 1.13 μm, and when the In composition is 36% and the thickness is 7.8 nm, the oscillation wavelength is 1.16 μm. When the In composition was 39% and the thickness was 7.2 nm, the oscillation wavelength was 1.2 μm. Moreover, the amount of compressive strain of each well layer 25a, 25b varied depending on the composition, and was about 2.2% to 2.7%.
[0065]
The growth method of each layer of the semiconductor light emitting device of FIG. 4 was performed by MOCVD. The raw materials are TMG (trimethylgallium), TMI (trimethylindium), AsH._Three(Arsine), PH_Three(Phosphine) is used and the carrier gas is H₂Was used. The GaInAs layer was grown at 550 ° C.
[0066]
FIG. 5 shows a threshold current density J with respect to the oscillation wavelength of the semiconductor light emitting device of FIG._thIt is shown. From FIG. 5, the oscillation wavelength of the semiconductor light emitting device of FIG. 4 is 1.13 to 1.23 μm, and the oscillation wavelength can be made longer than that of a GaInAs quantum well laser device grown on a conventional GaAs substrate. I understand. Further, the threshold value suddenly increases when the oscillation wavelength exceeds 1.2 μm, but the threshold current density J is increased to about 1.2 μm._thIs 200A / cm²It can be seen that it is low enough. Also, the characteristics at high temperature were good.
[0067]
In the above example, the semiconductor light emitting device is grown by the MOCVD method, but other growth methods such as the MBE method can also be used. In the semiconductor light emitting device of FIG. 4, an example of a double quantum well structure (DQW) is shown as the stacked structure of the active layer (light emitting layer), but a structure using quantum wells having other numbers of wells (SQW, MQW) can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure. However, the surface orientation of the GaAs substrate is preferably in the vicinity of (100), and the inclination angle of the surface orientation from (100) is preferably within a range of 5 °. Further, when GaInP is grown on a (100) substrate having a plane orientation (100) or slightly inclined by MOCVD or the like, a hill-like defect called hillock is likely to be formed. This is undesirable because it adversely affects device yield and light emission efficiency. Although the hillock density can be reduced by optimizing the growth conditions, it can be easily reduced by using GaInPAs containing As. The As composition is preferable because it has a slight effect.
[0068]
Example 2
6 is a view showing a semiconductor light emitting device of Example 2. FIG. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 6 has an SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 6 has an n-GaAs buffer layer 42 and an n-GaInP (As) lower cladding layer 43 (with a film thickness of 1.. 5 μm), a GaAs light guide layer 44 (film thickness is 100 nm), Ga_0.67In_0.33N_0.006As_0.994An active layer (light emitting layer) 47 composed of well layers 45a and 45b and a GaAs barrier layer 46 (thickness 13 nm), a GaAs light guide layer 48 (thickness 100 nm), and a p-GaInP (As) upper cladding layer 49 A (thickness is 1.5 μm) and p-GaAs contact layer 50 (thickness is 0.3 μm) are sequentially formed. In the semiconductor light emitting device of FIG. 6, the GaAs contact layer 50 is removed by etching except for the current injection portion, and the p-side electrode 52 is formed through the insulating film 51 from which the portion to be the current injection portion is removed. An n-side electrode 53 is formed on the back surface of the substrate 41.
[0069]
Here, the In composition x of each well layer 45a, 45b was 33%, and the nitrogen (N) composition was 0.6%. The thickness of each well layer 45a, 45b was 7 nm. Further, the amount of compressive strain of each of the well layers 45a and 45b was about 2.3%.
[0070]
The growth method of each layer of the semiconductor light emitting device of FIG. 6 was performed by MOCVD. The raw materials are TMG (trimethylgallium), TMI (trimethylindium), AsH._Three(Arsine), PH_Three(Phosphine) was used, and DMHy (dimethylhydrazine) was used as a nitrogen source. DMHy decomposes at low temperatures and is therefore suitable for low temperature growth at 600 ° C. or lower. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable. That is, since DMHy decomposes at a low temperature, it is suitable for a low temperature growth of 600 ° C. or lower, and is particularly preferable when a quantum well layer having a large strain required for low temperature growth is grown. In the present example, the GaInNAs well layers 45a and 45b were grown at 550 ° C. The carrier gas is H₂Was used.
[0071]
FIG. 7 shows current-output power (voltage) characteristics in the continuous operation of the semiconductor light emitting device of FIG. Where threshold current density J_th570A / cm²Met. The oscillation wavelength was about 1.24 μm. In the semiconductor light emitting device of FIG. 6, the threshold current density J is higher than that of the conventional GaInNAs laser device by making the In composition of the well layers 45a and 45b larger than 30% and the compressive strain amount being 2% or more._thWas dramatically reduced. Also, the characteristics at high temperature were good. The oscillation wavelength is variable by controlling the nitrogen composition, the In composition, the thickness of the well layer, and the like.
[0072]
In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 6, DMHy is used as the material for nitrogen (N) in the well layers 45a and 45b, but activated nitrogen or NH_ThreeOther nitrogen compounds can also be used. In the semiconductor light emitting device of FIG. 6, an example of a double quantum well structure (DQW) is shown as a stacked structure of active layers (light emitting layers), but a structure using quantum wells having other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.
[0073]
Example 3
FIG. 8 is a view showing a semiconductor light emitting device of Example 3. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 8 has a SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. The semiconductor light emitting device of FIG. 8 of Example 3 has substantially the same structure as that of FIG. 6 of Example 2, but the plane orientation of the n-GaAs substrate 41 is 2 ° from the (100) to the [011] direction. It is tilted at an angle. Further, the composition of the well layer is different from that of Example 2.
[0074]
That is, the semiconductor light emitting device of FIG. 8 has an n-GaAs buffer layer 62 and an n-GaInP (As) on an n-GaAs substrate 61 whose plane orientation is inclined at an angle of 2 ° from the (100) direction to the [011] direction. ) Lower cladding layer 63 (film thickness is 1.5 μm), GaAs light guide layer 64 (film thickness is 100 nm), Ga_0.6In_0.4N_0.005As_0.995An active layer (light emitting layer) 67 comprising well layers 65a and 65b and a GaAs barrier layer 66 (thickness 13 nm), a GaAs light guide layer 68 (thickness 100 nm), and a p-GaInP (As) upper cladding layer 69 A (thickness is 1.5 μm) and p-GaAs contact layer 70 (thickness is 0.3 μm) are sequentially formed. Further, in the semiconductor light emitting device of FIG. 8, the GaAs contact layer 70 is removed by etching except for the current injection portion, and the p-side electrode 72 is formed via the insulating film 71 from which the portion to be the current injection portion is removed. An n-side electrode 73 is formed on the back surface of the substrate 61.
[0075]
Here, the In composition x of each well layer 65a, 65b was 40%, and the nitrogen (N) composition was 0.5%. The thickness of each well layer 65a, 65b was 7 nm. This is the critical film thickness h based on Matthews and Blakeslee's theory._cThe condition is thicker than (about 6.1 nm). Further, the amount of compressive strain of each of the well layers 65a and 65b was about 2.7%.
[0076]
The growth method of each layer of the semiconductor light emitting device of FIG. 8 was performed by MOCVD. The raw materials are TMG (trimethylgallium), TMI (trimethylindium), AsH._Three(Arsine), PH_Three(Phosphine) was used, and DMHy (dimethylhydrazine) was used as a nitrogen source. DMHy decomposes at low temperatures and is therefore suitable for low temperature growth at 600 ° C. or lower. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable. In the present example, the GaInNAs well layers 65a and 65b were grown at 540 ° C. The carrier gas is H₂Was used.
[0077]
The oscillation wavelength of the semiconductor light emitting device of FIG. 8 produced in this way was about 1.3 μm. Also, the threshold current density J_thIs 1 kA / cm²It was the following. In GaInNAs lasers, the threshold current density tends to increase as the nitrogen composition increases. In the conventional 1.3 μm GaInNAs laser element, the nitrogen composition was 1% at the minimum (when the In composition was 30%). However, in the present invention, the In composition is made larger than 30% to compress the strain. By making the amount 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. Also, the characteristics at high temperature were good.
[0078]
In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 8, DMHy is used as a material for nitrogen (N) in the well layers 65a and 65b._ThreeOther nitrogen compounds can also be used. In the semiconductor light emitting device of FIG. 8, the example of the double quantum well structure (DQW) is shown as the stacked structure of the active layer (light emitting layer), but the structure using the quantum wells having other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.
[0079]
Example 4
FIG. 9 is a diagram showing a semiconductor light emitting device of Example 4. Here, an insulating film stripe type laser having the simplest structure will be described as an example of the semiconductor light emitting element. The semiconductor light emitting device of FIG. 9 has a SCH-DQW (Separate Confinement Heterostructure Double Quantum Well) structure as a layer structure. Specifically, the semiconductor light emitting device of FIG. 9 has an n-GaAs buffer layer 82, an n-GaInP on an n-GaAs substrate 81 whose plane orientation is inclined at an angle of 5 ° from the (100) direction to the [011] direction. (As) lower clad layer 83 (film thickness is 1.5 μm), GaAs light guide layer 84 (film thickness is 100 nm), Ga_0.65In_0.35N_0.007As_0.993GaNPAs barrier layers 86a, 86b, 86c (each film thickness is 10 nm) provided between well layers 85a, 85b and well layers 85a, 85b, below well layer 85a and above well layer 85b are formed. An active layer (light emitting layer) 87, a GaAs light guide layer 88 (film thickness is 100 nm), a p-GaInP (As) upper cladding layer 89 (film thickness is 1.5 μm), and a p-GaAs contact layer 90 (film) And a thickness of 0.3 μm) are sequentially formed. Further, in the semiconductor light emitting device of FIG. 9, the GaAs contact layer 90 is removed by etching except for the current injection portion, and the p-side electrode 92 is formed through the insulating film 91 from which the portion to be the current injection portion is removed. An n-side electrode 93 is formed on the back surface of the substrate 91.
[0080]
Here, the In composition x of each of the well layers 85a and 85b was 35%, and the nitrogen (N) composition was 0.7%. The thickness of each well layer 85a, 85b was 7 nm. The compressive strain amount of each well layer 85a and 85b was about 2.4%. At this time, the barrier layers 86a, 86b, 86c have tensile strain, and alleviate the compression of the well layers 85a, 85b.
[0081]
The growth method of each layer of the semiconductor light emitting device of FIG. 9 was performed by MOCVD. The raw materials are TMG (trimethylgallium), TMI (trimethylindium), AsH._Three(Arsine), PH_Three(Phosphine) was used, and DMHy (dimethylhydrazine) was used as a nitrogen source. DMHy is suitable for low temperature growth at 600 ° C. or lower because it decomposes at low temperatures. In particular, when a quantum well layer having a large strain is grown, a low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable. In the present example, the GaInNAs layer was grown at 520 ° C. The carrier gas is H₂Was used.
[0082]
The oscillation wavelength of the semiconductor light emitting device of FIG. 9 manufactured in this way was about 1.3 μm. Also, the threshold current density J_thIs 1 kA / cm²It was the following. In GaInNAs lasers, the threshold current density tends to increase as the nitrogen composition increases. In a conventional 1.3 μm band GaInAs laser element, the nitrogen composition was 1% at the minimum (when the In composition was 30%). However, in the present invention, the In composition is made larger than 30% and the compressive strain is increased. By making the amount 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. Furthermore, in Example 4, since the barrier layers 86b and 86c having tensile strain that relieve the compressive strain of the well layers 85a and 85b are further provided, the threshold current density is reduced as compared with the element of Example 3. Also, the characteristics at high temperature were good.
[0083]
In the above example, the semiconductor light emitting device is grown by MOCVD, but other growth methods such as MBE can be used. In the semiconductor light emitting device of FIG. 9, DMHy is used as a material for nitrogen (N) in the well layers 85a and 85b, but activated nitrogen or NH_ThreeOther nitrogen compounds can also be used. In the semiconductor light emitting device of FIG. 9, an example of a double quantum well structure (DQW) is shown as a stacked structure of active layers (light emitting layers), but a structure using quantum wells with other numbers of wells (SQW, MQW). ) Can also be used. The composition thickness of each layer can be changed and set as necessary. Further, the wide gap AlGaAs similar to GaInP (As) can be used for the cladding layer. Also, the structure of the laser may be another structure.
[0084]
Example 5
FIG. 10 is a diagram showing a semiconductor light emitting device (semiconductor laser) of Example 5. The semiconductor light emitting element shown in FIG. 10 is a surface emitting type. Since this semiconductor light emitting device constitutes a resonator for obtaining light emission, an upper reflecting mirror 109 is formed on the opposite side of the quantum well active layer 104 to the semiconductor substrate 101, and the quantum well active layer 104 A lower reflecting mirror 102 is formed on the semiconductor substrate 101 side, and at least the lower reflecting mirror 102 of the upper reflecting mirror 109 and the lower reflecting mirror 102 is composed of a low refractive index layer and a high refractive index layer made of a material not containing Al. Are configured as a semiconductor multilayer film alternately stacked. In this configuration, the upper reflecting mirror 109 and the lower reflecting mirror 102 function as resonators for light emission from the quantum well active layer 104.
[0085]
More specifically, the semiconductor light emitting device of FIG. 10 has an n-Ga lattice-matched to the GaAs substrate 101 on the n-GaAs substrate 101 having a plane orientation (100)._0.5In_0.5N-semiconductor multi-layer reflector having a periodic structure (35 periods) in which P and n-GaAs are alternately stacked at a thickness of 1/4 times the oscillation wavelength in each medium (GaInP / GaAs lower semiconductor multi-layer reflection) Mirror) 102, GaAs spacer layer 103, three layers of Ga_0.6In_0.4N_0.005As_0.995Multiple quantum well active layer (GaInNAs / GaAs QW active layer) 104 composed of As well layer and GaAs barrier layer (13 nm), GaAs spacer layer 105, Al_xO_yA current narrowing layer 106, a p-AlAs layer 107 (thickness of 50 nm) as a current injection portion, a p-GaAs contact layer 108, and a p-Ga lattice matched to the GaAs substrate 101_0.5In_0.5P-semiconductor multi-layer reflector having a periodic structure (30 periods) in which P and p-GaAs are alternately stacked at a thickness of 1/4 times the oscillation wavelength in each medium (GaInP / GaAs upper semiconductor multi-layer reflection) Mirror) 109 is grown sequentially.
[0086]
An insulating film (polyimide) 110 is formed on the side surfaces of the GaAs spacer layer 103, the quantum well active layer 104, the GaAs spacer layer 105, the current narrowing layer 106, and the p-GaAs contact layer 108. A p-side electrode 111 is formed on the p-GaAs contact layer 108, and an n-side electrode 112 is formed on the back surface of the GaAs substrate 101.
[0087]
The semiconductor light emitting device of FIG. 10 was produced as follows. That is, first, n-Ga lattice-matched to the GaAs substrate 101 on the n-GaAs substrate 101 having the plane orientation (100)._0.5In_0.5N-semiconductor multi-layer reflector having a periodic structure (35 periods) in which P and n-GaAs are alternately stacked at a thickness of 1/4 times the oscillation wavelength in each medium (GaInP / GaAs lower semiconductor multi-layer reflection) Mirror) 102, GaAs spacer layer 103, three layers of Ga_0.6In_0.4N_0.005As_0.995Multiple quantum well active layer (GaInNAs / GaAs QW active layer) 104 composed of As well layer and GaAs barrier layer (13 nm), GaAs spacer layer 105, Al_xO_yA current narrowing layer 106, a p-AlAs layer 107 (thickness of 50 nm) as a current injection portion, a p-GaAs contact layer 108, and a p-Ga lattice matched to the GaAs substrate 101_0.5In_0.5P-semiconductor multi-layer reflector having a periodic structure (30 periods) in which P and p-GaAs are alternately stacked at a thickness of 1/4 times the oscillation wavelength in each medium (GaInP / GaAs upper semiconductor multi-layer reflection) Mirror) 109 was grown sequentially.
[0088]
Here, the In composition x of the well layer was 40%, and the nitrogen composition was 0.5%. The thickness of the well layer was 7 nm. This is the critical film thickness h based on Matthews and Blakeslee's theory._cThe condition is thicker than (about 6.1 nm). The amount of compressive strain was about 2.7%. The growth method was the MOCVD method. Raw materials include TMG (trimethylgallium), TMI (trimethylindium), AsH_Three(Arsine), PH_Three(Phosphine), and DMHy (dimethylhydrazine) was used as a raw material for nitrogen.
[0089]
Since DMHy decomposes at low temperatures, it is suitable for low-temperature growth at 600 ° C. or lower. Moreover, when growing a quantum well layer with a large strain, a low temperature growth of, for example, about 500 ° C. to 600 ° C. is preferable. In Example 5, the GaInNAs layer was grown at 540 ° C. Since DMHy decomposes at low temperatures, it is suitable for low temperature growth such as 600 ° C. or lower, and is particularly preferable when growing a quantum well layer having a large strain required for low temperature growth. The carrier gas is H₂Was used.
[0090]
Then, mesa etching was performed in a circular shape having a diameter of 30 μm up to the upper portion of the lower multilayer film reflecting mirror 102 by photolithography and an etching process, and only the upper multilayer film reflecting mirror 109 was mesa etched in a circular shape having a diameter of 10 μm. Al_xO_yThe current narrowing portion 106 was formed by oxidizing AlAs having a side surface from the side surface with water vapor.
[0091]
Next, the etched portion is filled with an insulating film (polyimide) 110 and planarized, and the portion on which the p-side electrode 111 is to be formed and the polyimide on the upper multilayer mirror 109 serving as the light extraction port are removed, and p-GaAs is removed. A p-side electrode 111 was formed on the contact layer 108, and an n-side electrode 112 was formed on the back surface of the substrate 101.
[0092]
In the semiconductor light emitting device of FIG. 10, n-GaInP and n-GaAs not containing Al are used as the n-semiconductor multilayer reflector (lower semiconductor multilayer reflector) 102 between the semiconductor substrate 101 and the active layer 104. Therefore, the active layer 104 having a large strain could be easily grown without deteriorating.
[0093]
The lower semiconductor multilayer mirror 102 between the semiconductor substrate 101 and the active layer 104 does not contain Al, and a combination of a material having a large refractive index and a material having a small refractive index can be used. Specifically, in addition to the combination of GaInP (low refractive index layer) and GaAs (high refractive index layer), GaInPAs (low refractive index layer) and GaAs (high refractive index layer), GaInP (low refractive index layer) and GaInPAs ( High refractive index layer), GaInP (low refractive index layer) and GaPAs (high refractive index layer), GaInP (low refractive index layer) and GaInAs (high refractive index layer), GaInP (low refractive index layer) and GaInNAs (high refractive index) A combination such as a rate layer can be used. Of course, it is easier to grow an active layer having a large strain on the lower semiconductor multilayer film reflecting material using a material that does not contain Al, but even if a material containing Al is used. It can be used by optimizing the growth conditions. Specifically, a combination of AlAs (low refractive index layer) and GaAs (high refractive index layer), a combination of AlGaAs and GaAs, AlAs and AlGaAs, AlGaAs (large Al composition) and AlGaAs (low Al composition), etc. are used. be able to.
[0094]
Also, the upper semiconductor multilayer reflector 109 on the surface side of the active layer 104 (p-semiconductor multilayer reflector in this embodiment) does not contain Al and uses a combination of a material having a high refractive index and a material having a small refractive index. Can do. Specifically, in addition to the combination of GaInP (low refractive index layer) and GaAs (high refractive index layer), GaInPAs (low refractive index layer) and GaAs (high refractive index layer), GaInP (low refractive index layer) and GaInPAs ( High refractive index layer), GaInP (low refractive index layer) and GaPAs (high refractive index layer), GaInP (low refractive index layer) and GaInAs (high refractive index layer), GaInP (low refractive index layer) and GaInNAs (high refractive index) A combination such as a rate layer can be used.
[0095]
However, the upper semiconductor multilayer reflector 109 on the surface side of the active layer 104 (p-semiconductor multilayer reflector in this embodiment) may contain Al. Specifically, a combination of AlAs (low refractive index layer) and GaAs (high refractive index layer), a combination of AlGaAs and GaAs, AlAs and AlGaAs, AlGaAs (large Al composition) and AlGaAs (low Al composition), etc. are used. be able to. In this case, since the active layer 104 having a large strain is grown at a low temperature, the active layer 104 is preferably grown at a temperature as low as possible (for example, 700 ° C. or lower). In addition, a dielectric multilayer film can be used as the upper semiconductor multilayer film reflecting mirror 109. Specifically, TiO₂And SiO₂A combination of the above can be used.
[0096]
The surface emitting laser (semiconductor laser shown in FIG. 10) produced in this way had an oscillation wavelength of about 1.3 μm. The threshold current density is 1 kA / cm.²It was the following. By making the In composition larger than 30% and the compressive strain amount being 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. The characteristics at high temperature were also good. It also had a long life.
[0097]
In the fifth embodiment, an example of the growth by the MOCVD method is shown, but other growth methods such as the MBE method can also be used. Also, DMHy was used as a nitrogen source, but activated nitrogen and NH_ThreeOther nitrogen compounds can also be used.
[0098]
In the above example, an example of a triple quantum well structure (TQW) is shown as a stacked structure, but a structure using quantum wells with other numbers of wells (SQW, MQW) or the like can also be used. Further, the composition thickness of each layer can be set to other values as required. Further, GaInAs can be used for the active layer 104. The structure of the laser may be another structure.
[0099]
Example 6
FIG. 11 is a diagram showing a semiconductor light emitting device (semiconductor laser) of Example 6. The semiconductor light emitting element shown in FIG. 11 is a surface emitting type. Since this semiconductor light emitting device constitutes a resonator for obtaining light emission, an upper reflecting mirror 128 is formed on the side of the quantum well active layer 123 opposite to the semiconductor substrate 121, and the quantum well active layer 123 A lower reflecting mirror 129 is formed on the semiconductor substrate 121 side, and at least the lower reflecting mirror 129 of the upper reflecting mirror 128 and the lower reflecting mirror 129 has a low refractive index layer and a high refractive index layer made of a dielectric material. It is configured as a dielectric multilayer film laminated alternately. Also in this configuration, the upper reflecting mirror 128 and the lower reflecting mirror 129 function as resonators for light emission from the quantum well active layer 123.
[0100]
More specifically, the semiconductor light emitting device of FIG. 11 has an n-GaInPAs clad layer 122 (film thickness: 0.5 μm), 3 lattice-matched to the GaAs substrate 121 on the n-GaAs substrate 121 having a plane orientation (100). Layer Ga_0.6In_0.4N_0.005As_0.995Multiple quantum well active layer (GaInNAs / GaAsQW active layer) 123 composed of As well layer and GaAs barrier layer, p-GaInPAs cladding layer 124 (film thickness is 1.5 μm), Al_xO_yThe current narrowing layer 125, the AlAs layer 126 (thickness of 50 nm) as a current injection portion, the p-GaAs contact layer 127 (thickness of 0.3 μm), p-AlAs and p-GaAs are oscillated in the respective media. A p-semiconductor multilayer reflector (AlGaAs / GaAs upper semiconductor multilayer reflector) 128 having a periodic structure (21 periods) alternately laminated with a thickness of 1/4 of the thickness is sequentially grown. In the semiconductor light emitting device of FIG. 11, a part of the GaAs substrate 121 is etched to the surface of the cladding layer 122, and the TiO 2 is formed on the cladding layer 122.₂And SiO₂Dielectric multilayer reflector (TiO) consisting of₂/ SiO₂A lower dielectric multilayer mirror) 129 is formed.
[0101]
An insulating film (polyimide) 130 is formed on the side surfaces of the current narrowing layer 125 and the p-GaAs contact layer 127, and a p-side electrode 131 is formed on the p-GaAs contact layer 127. An n-side electrode 132 is formed on the back surface of the substrate 121.
[0102]
The semiconductor light emitting device of FIG. 11 was produced as follows. That is, first, an n-GaInPAs clad layer 122 (having a film thickness of 0.5 μm) lattice-matched to the GaAs substrate 121 on the n-GaAs substrate 121 having a plane orientation (100), and three layers of Ga_0.6In_0.4N_0.005As_0.995Multiple quantum well active layer (GaInNAs / GaAs QW active layer) 123 composed of As well layer and GaAs barrier layer, p-GaInPAs clad layer 124 (film thickness is 1.5 μm), Al_xO_yThe current narrowing layer 125, the AlAs layer 126 (thickness of 50 nm) as a current injection portion, the p-GaAs contact layer 127 (thickness of 0.3 μm), p-AlAs and p-GaAs are oscillated in the respective media. P-semiconductor multilayer mirror (AlGaAs / GaAs upper semiconductor multilayer mirror) 128 having a periodic structure (21 periods) alternately stacked at a thickness of 1/4 of the thickness was sequentially grown.
[0103]
Here, the In composition x of the well layer was 40%, and the nitrogen composition was 0.5%. The thickness of the well layer was 7 nm. The amount of compressive strain was about 2.7%. The growth method was the MOCVD method. Raw materials include TMG (trimethylgallium), TMI (trimethylindium), AsH_Three(Arsine), PH_Three(Phosphine), and DMHy (dimethylhydrazine) was used as a raw material for nitrogen. The p-semiconductor multilayer reflector 128 containing Al was grown at a low temperature of 680 ° C., which has little influence on the active layer 123.
[0104]
Then, mesa etching was performed in a circular shape having a diameter of 10 μm up to the upper portion of the p-semiconductor multilayer reflector 128 by photolithography and an etching process, and the p-GaAs contact layer 127 was further mesa-etched in a circular shape having a diameter of 30 μm. Then, an insulating film (polyimide) 130 was coated and the current injection portion 126 was opened to form a p-side electrode 131. Then, the semiconductor substrate 121 is etched until the surface of the n-GaInPAs cladding layer 122 appears, and TiO₂And SiO₂A dielectric multilayer film reflecting mirror 129 made of a combination of the above was formed. Further, an n-side electrode 132 was formed on the back surface of the substrate 121. In such a structure, the light extraction portion is the back surface of the substrate 121.
[0105]
In the sixth embodiment, the semiconductor multilayer film reflector is not inserted between the semiconductor substrate 121 and the active layer 123 having a large strain, and the dielectric multilayer film is used as the reflector on the substrate 121 side. The active layer 123 can be easily grown without deteriorating.
[0106]
In other words, the reflecting mirror on the semiconductor substrate side is formed outside the semiconductor portion, and the semiconductor layer containing Al is not formed between the semiconductor substrate and the quantum well active layer having a large strain. The state of the epi-substrate surface during growth was good, and a large strained quantum well layer could be easily and satisfactorily grown.
[0107]
The surface emitting laser produced in this way had an oscillation wavelength of about 1.3 μm. The threshold current density is 1 kA / cm.²It was the following. By making the In composition larger than 30% and the compressive strain amount being 2% or more, the nitrogen composition can be made smaller than before, and the threshold current density can be dramatically reduced. The characteristics at high temperature were also good.
[0108]
In the sixth embodiment, the example of the growth by the MOCVD method is shown, but other growth methods such as the MBE method can also be used. Also, DMHy was used as a nitrogen source, but activated nitrogen and NH_ThreeOther nitrogen compounds can also be used.
[0109]
In the above example, an example of a triple quantum well structure (TQW) is shown as a stacked structure, but a structure using quantum wells with other numbers of wells (SQW, MQW) or the like can also be used. Further, the composition thickness of each layer can be set to other values as required. Alternatively, GaInAs can be used for the active layer 123. The structure of the laser may be another structure.
[0110]
The quality of an active layer having such a large strain is very sensitive to the structure and growth conditions, and the present invention has been described in detail. Even if it is less than 2%, it is effective.
[0111]
In each of the above-described embodiments, when a GaAs substrate is used as the semiconductor substrate, an example in which GaInAs and GaInNAs are used as the semiconductor material on the GaAs substrate has been shown, but in addition to this, a GaAs substrate is used as the semiconductor substrate. When using GaInP, GaPAs as the semiconductor material on the GaAs substrate, or when using an InP substrate as the semiconductor substrate, such as when using GaInAs, GaInPAs, InPAs, InNPAs, etc. as the semiconductor material on the InP substrate. Also, the present invention can be applied. That is, the present invention is effective for a semiconductor light emitting device using a semiconductor having a lattice constant that is significantly different from that of the semiconductor substrate. The present invention can also be applied to semiconductor elements using III-V mixed crystal semiconductors such as other light emitting elements, light receiving elements or electronic elements.
[0112]
【The invention's effect】
  As described above, according to the first aspect of the present invention, an active layer including a strained quantum well layer having a strain amount exceeding 2% and a cladding layer for confining light and carriers are provided on a semiconductor substrate.And III -V group semiconductor formedManufacturing method of semiconductor light emitting deviceBecause III The semiconductor light emitting device is formed by metal organic vapor phase epitaxy using an organometallic compound as a group source material, and the strained quantum well layer is formed of Ga. _x In _1-x N _y As _1-y ( 0 ≦ x ≦ 1, 0 <y <1 ) As a raw material for N, DMHy ( Dimethylhydrazine ) , MMHy ( Monomethylhydrazine ) Using organic nitrogen compounds such asThe strained quantum well layerTheGrowth at temperatures below 600 ° CThe active layer is grown, and then the cladding layer is grown at a temperature of 700 ° C. or lower. Here, the metal organic vapor phase growth method is a growth method with a high degree of supersaturation, and is effective as a growth means for a high strain quantum well layer or a material such as GaInNAs containing nitrogen in the V group. According to the invention of claim 1, the strained quantum well layer is made of Ga. _x In _1-x N _y As _1-y ( 0 ≦ x ≦ 1, 0 ≦ y <1 ) As a raw material for N, DMHy ( Dimethylhydrazine ) , MMHy ( Monomethylhydrazine ) It forms using organic nitrogen compounds, such as. That is, since organic nitrogen compounds decompose at low temperatures, they are suitable for low temperature growth at 600 ° C. or lower. Further, when a quantum well layer having a particularly large strain is grown as in the present invention, for example, low temperature growth of about 500 ° C. to 600 ° C. is preferable, and an organic nitrogen compound that decomposes at a low temperature is also preferable from this viewpoint.That is, since the critical film thickness of the strained quantum well layer becomes thick at low temperatures, a low temperature growth of 600 ° C. or lower is suitable for the growth of high strained quantum well layers exceeding 2%.According to the first aspect of the present invention, since the clad layer is grown at a temperature of 700 ° C. or lower after the active layer is grown, AlGaAs can be used.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration example of a semiconductor light emitting element according to the present invention.
2 is a diagram illustrating an example of an active layer of the semiconductor light emitting device of FIG. 1;
FIG. 3 shows a PL characteristic of a semiconductor light emitting device formed on a GaAs substrate having a plane orientation of (100), and a GaAs substrate having a plane orientation inclined at an angle of 15 ° from the (100) direction to the [011] direction. It is a figure which shows the PL characteristic of the semiconductor light-emitting device formed in FIG.
4 is a view showing a semiconductor light emitting device of Example 1. FIG.
5 is a diagram showing a threshold current density with respect to an oscillation wavelength of the semiconductor light emitting device of FIG.
6 is a view showing a semiconductor light emitting device of Example 2. FIG.
7 is a diagram showing current-voltage characteristics in continuous operation of the semiconductor light emitting device of FIG.
8 is a view showing a semiconductor light emitting device of Example 3. FIG.
9 is a view showing a semiconductor light emitting device of Example 4. FIG.
10 is a view showing a semiconductor light emitting device of Example 5. FIG.
11 is a view showing a semiconductor light emitting device of Example 6. FIG.
FIG. 12 is a diagram showing PL characteristics of four samples a, b, c, and d.
FIG. 13 is a diagram showing PL characteristics of a sample using GaInP and a sample using AlGaAs as a guide layer.
FIG. 14 is a diagram showing the critical film thickness of a GaInAs layer on a GaAs substrate calculated based on the generally supported Matthews and Blakeslee theory.
FIG. 15 is a diagram showing a relationship between a PL center wavelength and a PL intensity from a GaInAs single quantum well layer.
[Explanation of symbols]
1 Semiconductor substrate
3 Active layer
2 Strained quantum well layer
4 Clad layer
5 Barrier layer
21 n-GaAs substrate
22 n-GaAs buffer layer
23 n-GaInP (As) lower clad layer
24 GaAs light guide layer
25a, 25b Ga_1-xIn_xAs quantum well layer
26 GaAs barrier layer
27 Active layer (light emitting layer)
28 GaAs light guide layer
29 p-GaInP (As) upper clad layer
30 p-GaAs contact layer
32 p-side electrode
31 Insulating film
33 n-side electrode
41 n-GaAs substrate
42 n-GaAs buffer layer
43 n-GaInP (As) lower cladding layer
44 GaAs light guide layer
45a, 45b Ga_0.67In_0.33N_0.006As_0.994Quantum well layer
46 GaAs barrier layer
47 Active layer (light emitting layer)
48 GaAs light guide layer
49 p-GaInP (As) upper clad layer
50 p-GaAs contact layer
52 p-side electrode
51 Insulating film
53 n-side electrode
61 n-GaAs substrate
62 n-GaAs buffer layer
63 n-GaInP (As) lower clad layer
64 GaAs light guide layer
65a, 65b Ga_0.6In_0.4N_0.005As_0.995Quantum well layer
66 GaAs barrier layer
67 Active layer (light emitting layer)
68 GaAs light guide layer
69 p-GaInP (As) upper clad layer
70 p-GaAs contact layer
72 p-side electrode
71 Insulating film
73 n-side electrode
81 n-GaAs substrate
82 n-GaAs buffer layer
83 n-GaInP (As) lower clad layer
84 GaAs light guide layer
85a, 85b Ga_0.65In_0.35N_0.007As_0.993Quantum well layer
86a, 86b, 86c GaAs barrier layer
87 Active layer (light emitting layer)
88 GaAs light guide layer
89 p-GaInP (As) upper clad layer
90 p-GaAs contact layer
92 p-side electrode
91 Insulating film
93 n-side electrode
101 GaAs substrate
102 Lower Semiconductor Multilayer Reflector
103 GaAs spacer layer
104 Active layer
105 GaAs spacer layer
106 Current constriction layer
107 Current injection layer
108 p-GaAs contact layer
109 Upper Semiconductor Multilayer Reflector
110 Insulating film
111 p-side electrode
112 n-side electrode
121 GaAs substrate
122 GaInPAs cladding layer
123 Active layer
124 GaInPAs cladding layer
125 Current constriction layer
126 Current injection part
127 p-GaAs contact layer
128 Upper Semiconductor Multilayer Reflector
129 Lower dielectric multilayer reflector
130 Insulating film
131 p-side electrode
132 n-side electrode

Claims (1)

On a semiconductor substrate, an active layer comprising a strained quantum well layer strain amount exceeds 2%, have a cladding layer for confining light and carriers, in the manufacturing method of the semiconductor light emitting element formed of a III -V semiconductors The semiconductor light emitting device is formed by metal organic vapor phase epitaxy using an organometallic compound as a group III raw material, and the strained quantum well layer is formed of Ga _x In _{1 -x} N _y As _{1 -y.} (0 ≦ x ≦ 1,0 <y <1) the case of forming, as a raw material of N, DMHy (dimethylhydrazine), 600 the strained quantum well layer with organic nitrogen compounds such as MMHy (monomethyl hydrazine) A method for manufacturing a semiconductor light-emitting device , comprising: growing at a temperature of less than or equal to ° C., growing the active layer, and then growing the cladding layer at a temperature of less than or equal to 700 ° C.

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