JP2004186509A - Gallium nitride system compound semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the light-emitting efficiency in a GaN system semiconductor device. <P>SOLUTION: An n-SLS layer 20, an active layer 22, a p-block layer 24, and a p-SLS layer 26 are sequentially laminated on a substrate 10. An AlGaN barrier layer/InGaN well layer/AlGaN barrier layer is used as the active layer 22, and a difference in an Al composition of the barrier layer is set to ≤3% to make the barrier symmetrical. Further, the Al composition of the barrier layer is set to ≥5%, preferably ≥10%. By making the barrier symmetrical, the light-emitting efficiency at the time of a low injected current is enhanced and the Al composition is set to a predetermined value or above, thereby enhancing the light-emitting efficiency at the time of a high injected current. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００２６】
図２には、図１において活性層２２のみを抜き出した構成が示されている。活性層２２は、既述したようにＡｌ_ｘＧａ_１−ｘＮ層（ｎ側バリア層２２ａ）、Ｉｎ_ｙＧａ_１−ｙＮ層（井戸層２２ｂ）、Ａｌ_ｚＧａ_１−ｚＮ層（ｐ側バリア層２２ｃ）から構成されており、表１に示すように組成比ｘ、ｙ、ｚは、
５％≦ｘ≦２５％
０％＜ｙ≦１５％
５％≦ｚ≦２５％ ・・・・（１）
を満たす場合に１ｍＷ以上の発光出力が得られる。井戸層２２ｂを挟むバリア層２２ａ、２２ｃに関しては、その組成比ｘとｚは実質的に等しいことが好適であり、具体的には
｜ｘ−ｚ｜≦３％ ・・・・（２）
であることが望ましい。
【００２７】
表２には、井戸層２２ｂのＡｌ組成比ｙを固定し、ｎ側バリア層２２ａ及びｐ側バリア層２２ｃのＡｌ組成比ｘ、ｚを変化させたときの発光強度が示されている。
【００２８】
【表２】

【００２９】
表２において、サンプル（ａ）はｎ側バリア層２２ａ及びｐ側バリア層２２ｃがともに７％と対称の場合、サンプル（ｂ）はｎ側バリア層２２ａが７％、ｐ側バリア層２２ｃが１２％と非対称な場合、サンプル（ｃ）はｎ側バリア層２２ａ及びｐ側バリア層２２ｃがともに１２％と対称な場合である。光出力は、２０ｍＡ及び１００ｍＡを注入したときのサンプル（ｃ）の光出力を基準値１とする相対値である。また、図３には、注入電流を変化させたときのサンプル（ａ）、（ｂ）、（ｃ）の光出力が示されており、図４にはサンプルの発光スペクトルが示されている。各サンプルの発光波長は、ウエハ面内で多少のばらつきはあるものの３７０ｎｍ±５ｎｍの範囲内である。
【００３０】
表２及び図３から分かるように、ｎ側バリア層２２ａ及びｐ側バリア層２２ｃのＡｌ組成比を変化させることで発光出力は大きく変化する。そして、ｎ側バリア層２２ａとｐ側バリア層２２ｃのＡｌ組成比ｘ、ｚをほぼ同一とし、これらの組成比をある値以上に設定することが有効である。
【００３１】
すなわち、サンプル（ａ）とサンプル（ｂ）とを比較すると、サンプル（ａ）はサンプル（ｂ）よりもｐ側バリア層２２ｃのＡｌ組成比が小さいにもかかわらず、注入電流が小さい場合に高い光出力が得られる。一般に、Ａｌ組成比を大きくするとバンドギャップが増大してキャリアの閉じ込め効果が増大すると考えられるが、本実施形態の結果はこの考えでは説明できない。一方、Ａｌ組成比がサンプル（ａ）より大きいサンプル（ｃ）では光出力が増大していることから、Ａｌ組成比の増大による結晶の劣化が原因とは考えられない。したがって、表２及び図３の結果は、結晶歪みによるものと考えられる。バリア層の材料であるＡｌＧａＮと井戸層の材料であるＩｎＧａＮは格子定数が異なるためこれらのヘテロ接合をＧａＮ層の上に形成すると両者に結晶歪みが生じる。特に、これらの層が薄い場合には結晶は弾性的に歪むため転位は生じない。また、ｃ軸が基板面に対して垂直となるように結晶成長されたＡｌＧａＮとＩｎＧａＮに面内歪みが加わった場合、これらの材料が有する圧電性により基板面に垂直に電界が発生する。この垂直電界は活性層２２のバンド構造に傾きを形成し、活性層２２に注入された電子・正孔対を分離させて発光効率を低下させる。
【００３２】
図５及び図６には、活性層２２のバンド図が示されている。図５はサンプル（ａ）、（ｃ）のようにＡｌ組成比がｎ側バリア層２２ａとｐ側バリア層２２ｃで対称（実質的に同一）の場合のバンド図であり、図６はサンプル（ｂ）のようにＡｌ組成比がｎ側バリア層２２ａとｐ側バリア層２２ｃで非対称（実質的に非同一）の場合のバンド図である。また、両図において、（Ａ）は伝導帯の予想バンド図、（Ｂ）は価電子帯のバンド図である。
【００３３】
図６に示される様に、非対称バリアに挟まれたＩｎＧａＮ井戸層２２ｂの中には図５で示される対称バリアの場合よりも大きな歪みがかかり、その結果、より大きな電界が印加されて電子・正孔対を空間的に分離し発光効率の低下を招く。電流を増加させると井戸層２２ｂの中に注入されたキャリア密度が増加し、その電荷により歪み電界が打ち消される（クーロンスクリーニング効果）。従って、サンプル（ｂ）のように非対称構造の場合、電流を増加させると発光効率が急激に増大し、５０ｍＡを超えるとｐ側バリア層２２ｃのより高いキャリア閉じ込め効果により発光効率はサンプル（ａ）を上回るようになると考えられる。一方、サンプル（ｃ）においては対称バリアと高い閉じ込め効果により発光効率はサンプル（ａ）、（ｂ）よりも大きくなる。
【００３４】
このように、ｎ側バリア層２２ａとｐ側バリア層２２ｃのＡｌ組成を実質的に同一として対称バリアを形成することで井戸層２２ｂ中の歪みを抑制し、低注入電流時の発光効率を向上させることができる。また、ｎ側バリア層２２ａ及びｐ側バリア層２２ｃのＡｌ組成比は高注入電流時のキャリア閉じ込め効果に影響を与え、Ａｌ組成比が小さすぎると高注入電流時の発光効率が低下してしまう。以上より、（１）の条件と（２）の条件が発光効率向上に有効であることがわかる。
【００３５】
活性層２２のより好ましい組成比を示すと以下のようになる。
【００３６】
１０％≦ｘ≦１５％
０％＜ｙ≦１５％
１０％≦ｚ≦１５％ ・・・・（３）
ｘ及びｙの下限は高注入電流時のキャリア閉じ込め効果を考慮したものであり、上限は結晶劣化を考慮したものである。
【００３７】
なお、活性層２２の各層の膜厚に関しては、表１に示されるように、ｎ側バリア層２２ａは５ｎｍ以上２０ｎｍ以下、井戸層２２ｂは１ｎｍ以上２．５ｎｍ以下、ｐ側バリア層２２ｃは５ｎｍ以上２０ｎｍ以下であれば所望の発光出力が得られることを確認している。
【００３８】
また、ｎ−ＳＬＳ層２０及びｐ−ＳＬＳ層２６に関しては、活性層２２よりもバンドギャップが大きく活性層２２にキャリアを注入するクラッド層として機能することからＡｌ組成比が決定される。活性層２２が上記の（１）、（２）の条件を満たす場合、ｎ−ＳＬＳ層２０及びｐ−ＳＬＳ層２６が満たすべき条件は以下の通りである。
【００３９】
５％≦α≦３０％
５％≦β≦３０％ ・・・・（４）
また、ｐ−ブロック層２４に関しては、電子がｐ型層中に注入されて再結合することにより発光効率が低下することを抑制するため、活性層２２の井戸層２２ｂ及びｐ側バリア層２２ｃよりもバンドギャップが大きくなるように設定される。すなわち、ｐ−ブロック層２４が満たすべき条件は
ｚ＋５％≦γ ・・・・（５）
であり、具体的に示すと
１０％≦γ≦３０％ ・・・・（６）
である。
【００４０】
本実施形態において、最良と考えられる組成比を示すと以下の通りである。
【００４１】
ｎ−ＳＬＳ層２０：
ｎ−Ａｌ_０．１８Ｇａ_０．８２Ｎ／ｎ−ＧａＮ
活性層（発光層）２２：
Ａｌ_０．１２Ｇａ_０．８８Ｎ／Ｉｎ_０．１３Ｇａ_０．８７Ｎ／Ａｌ_０．１２Ｇａ_０．８８Ｎ
ｐ−ブロック層２４：
Ａｌ_０．１８Ｇａ_０．８２Ｎ
ｐ−ＳＬＳ層２６
ｐ−Ａｌ_０．１８Ｇａ_０．８２Ｎ／ｐ−ＧａＮ
もちろん、これらの組成は例示であり、当業者であれば上記の範囲内において任意の組成を選択することが可能である。また、本実施形態では、基本的にｎ型クラッド層２０／活性層２２／ｐ型ブロック層２４／ｐ型クラッド層２６の構成であるが、例えばｐ型ブロック層２４を省く、あるいは活性層２２とクラッド層との間にさらに機能層を追加することも可能であり、これらはいずれも本発明の変形例である。
【００４２】
本実施形態では、活性層２２として井戸層２２ｂをバリア層２２ａ、２２ｃで挟んだＳＱＷ構造を用いているが、ｎ側バリア層２２ａ／井戸層２２ｂ／ｐ側バリア層２２ｃの構成を複数周期積層したＭＱＷ（多層量子井戸）構造を用いることも可能である。ＭＱＷを用いた場合にも、井戸層を挟むバリア層のＡｌ組成比の差を３％以下に抑えることで、特に低注入電流における発光効率を向上させることができる。
【００４３】
このように、本実施形態におけるＬＥＤは、波長４００ｎｍ以下で高い発光効率を有するため、この特性を専ら利用して種々の製品を作製することが可能である。以下では、図１に示されたＬＥＤあるいは発光素子を光源として用いるいくつかの装置例を示す。
【００４４】
＜第２実施形態＞
市販のブラックペン（蛍光ペン）（シンロイヒ製）は可視照明下で文字や図形等を描いても見えないが、そこに紫外線を照射すると描いた文字や図形が現れる。カラーのブラックペン（紫外線を照射するとカラーの図形が現れる）も市販されているが、カラーを再現するためには照射する紫外線の波長が４００ｎｍ以下、より正確には波長３８０ｎｍ以下でなければならない。従来においては、蛍光灯ブラックライトや水銀ランプ等の光源が使用されているが、大型で消費電力も大きく、電源も大掛かりになる欠点がある。
【００４５】
そこで、図形再現用光源として図１に示された発光素子デバイス（ＬＥＤ）を用いると、小型で電池駆動も可能となる。ブラックペンで描いた図形を、ピーク波長４００ｎｍ、３８５ｎｍ、３７２ｎｍのＬＥＤで照射して図形の再現を試みた。照射光強度はおよそ５ｍＷ（４００ｎｍ）、３ｍＷ（３８５ｎｍ）、１ｍＷ（３７２ｎｍ）である。
【００４６】
４００ｎｍＬＥＤの場合、図形が現れるものの色は再現されず、蛍光の強度もかろうじて見える程度の非常に低いレベルであった。３８５ｎｍＬＥＤで照射すると、図形の形ははっきり見える程度に強い蛍光強度は得られたが、色は再現されなかった。特に、赤色の再現性が悪かった。一方、波長３７２ｎｍＬＥＤの場合、照射強度が１ｍＷと弱いにもかかわらず、蛍光は明るい室内でも全く問題なく見える程度に強く、かつ３原色を忠実に再現できた。
【００４７】
これらより、波長３６５〜３８０ｎｍ帯のＬＥＤは、安価に市販されているブラックペン（蛍光ペン）で描いた図形の再現用光源として非常に適していることが確認された。本実施形態のＬＥＤを電池と共にキーホルダやブラックペン、消しゴムその他の製品に組み込んで簡単に再現できる、見えない文字や図形を描画するシステムが得られる。
【００４８】
＜第３実施形態＞
本実施形態におけるＬＥＤからの光を人体の皮膚に短時間照射してその影響を調べた。ピーク波長４００ｎｍ（５ｍＷ）、３８５ｎｍ（３ｍＷ）、３７２ｎｍ（１ｍＷ）のＬＥＤ光をそれぞれ１０分間皮膚に照射して皮膚の変化（いわゆる日焼け）を調べた。その結果、ピーク波長４００ｎｍ（５ｍＷ）の場合はほとんど影響が見られなかったのに対し、３８５ｎｍ（３ｍＷ）の場合は少し変化が見られた。一方、３７２ｎｍ（１ｍＷ）の場合には、はっきりした跡が見られた。このことは、波長３６５〜３８０ｎｍ帯のＬＥＤが人体の日焼けを起こすことを示している。このＬＥＤを光源として用いて日焼け装置を製作した。直径５ｍｍのスポットだけを日焼けする装置及びＬＥＤを長さ３ｃｍの直線上に配置して線条に日焼けする装置を作製し、実験を行った。いずれの装置も１０分間照射することで日焼けが得られた。なお、３０分以上照射すると皮膚の損傷が認められた。
【００４９】
従来、日焼け装置は紫外線のランプを使用しているため、照射面積が大きい用途には適当であったが、小さな領域だけの日焼けを作ることはできず、例えば日焼けしたい部位以外をタオルなどで覆うなどの工夫が必要であるところ、本実施形態の日焼け装置では、点や線などの日焼けを任意に作ることが可能である。
【００５０】
＜第４実施形態＞
市販されているＵＶカット化粧品（ＳＰＦ５０＋ＰＡ＋＋＋）を塗った皮膚に対し、ピーク波長３７２ｎｍ（１ｍＷ）のＬＥＤを光源に組み込んだ第３実施形態の日焼け装置で１０分間照射した。その結果、ＵＶカット化粧品を塗らない場合と比べて日焼けの程度が非常に小さいことを確認した。このように、本実施形態のＬＥＤは、ＵＶカット化粧品の性能を評価する装置として用いることもできる。
【００５１】
従来、この種の検査装置は大型であり、効果を調べるために広い皮膚表面が必要である。本実施形態の検査装置は、上述した実施形態で述べたように点あるいは線等の任意の形状あるいは部位に日焼けを作ることができるので、人体の部位毎の日焼けの程度を調べたり、あるいは携帯して長時間にわたる照射効果を調べることもできる。
【００５２】
＜第５実施形態＞
時計の文字盤や避難誘導等の標識類には蓄光材料が使用されている。これは、蓄光剤に光が当たると、光を消しても蛍光が続くことを利用して暗闇でも字等が読める仕組みを利用したものである。近年、蓄光時間も長くなり３原色も出せるようになっている。例えば、硫化亜鉛に銅を結合させた短残光タイプやストロンチウムアルミネイトに希土類金属を結合させた長残光タイプなどが知られている。このような蓄光剤の感度は一般に波長４００ｎｍ以下にある。したがって、蓄光剤と本実施形態のＬＥＤとを組み合わせることで、短時間のみ光を照射して光を消すという操作を繰り返すことで消費電力の非常に小さい表示装置を作製することができる。また、電源が切れても表示は消えない（不揮発な）非常用表示装置も可能となる。
【００５３】
ピーク波長４００ｎｍ（５ｍＷ）、３８５ｎｍ（３ｍＷ）、３７２ｎｍ（１ｍＷ）のＬＥＤと３原色の蓄光剤を組み合わせて表示装置を作製した。蓄光剤を板状に加工し、その裏面から実施形態のＬＥＤの光を照射して表面からの発光を観測した。１０分間照射し、決められた時間だけ照射を切るサイクルを繰り返した。３０分程度照射を切っても、事務室程度の明るさの部屋で蓄光剤からの発光が確認された。なお、暗闇中では１時間程度切っても蓄光剤からの発光が確認された。全ての波長で同様の効果が得られたが、ピーク波長４００ｎｍ（５ｍＷ）を光源として使用した場合に最も残光が強かった。
【００５４】
このように、波長３６５〜４００ｎｍ帯のＬＥＤと蓄光剤を使用した表示装置により、従来の表示装置と比べて消費電力を著しく低減することができる。
【００５５】
さらに、色の再現性についても観測した。ピーク波長４００ｎｍ（５ｍＷ）、３８５ｎｍ（３ｍＷ）のＬＥＤは、肉眼には青色〜紫色に見えるため、蓄光剤で赤色を出すと両者が混じり合い純粋な赤の再現はできない。緑も同様である。一方、ピーク波長３７２ｎｍ（１ｍＷ）のＬＥＤは肉眼ではほとんど見えないため、３原色を忠実に再現することができる。したがって、波長３６５〜３８０ｎｍ帯のＬＥＤを光源として用い、蓄光剤を使用した表示装置は低消費電力で、かつ、フルカラーを再現することができる。
【００５６】
＜第６実施形態＞
蛾等の昆虫の複眼は、波長３６０ｎｍにピーク感度を有する。その性質を利用して、紫外線ランプを使った昆虫の駆除装置が市販されている。紫外線ランプを街頭に付け、その周辺に昆虫駆除装置を取り付けたものである。紫外線ランプは、可視光も射出するので一般的には明るく見える。また、消費電力が大きいという問題がある。この昆虫収集用の光源として実施形態のＬＥＤを使用した。ピーク波長は３７２ｎｍである。暗闇にＬＥＤを設置し、昆虫の集まり状況を確認した。同時に、２Ｗの水銀ランプも比較のため別の場所に設置した。ＬＥＤの消費電力を節約するため及び発光ピーク強度を増すため、ピーク電流２００ｍＡ、ピーク出力約１０ｍＷ、パルス幅１０ｍＳ、繰り返し周波数１０Ｈｚ（平均出力１ｍＷ）のパルス駆動を行った。光出力は、ＬＥＤの方が小さいにもかかわらずより多くの昆虫がＬＥＤに集まることが観測された。水銀ランプは肉眼には青色〜紫色に見えたが、ＬＥＤはほとんど肉眼では確認できなかった。このことから、昆虫収集用の光源として、波長３６５〜３８０ｎｍ帯のＬＥＤが使えることがわかる。
【００５７】
そこで、市販の昆虫駆除装置のランプをＬＥＤに取り替えて装置を作製した。波長３７２ｎｍのＬＥＤを２００個使用して、上述した実験と同様にパルス駆動して動作させた。その結果、一晩で改造前と同程度の昆虫を駆除することができた。本実施形態のＬＥＤを光源に用いた昆虫駆除装置は、消費電力が小さく、ＬＥＤが小型であるため光源のレイアウトに自由度が増すというメリットがある。さらに、肉眼ではほとんど見えないので、照明を嫌う環境にも用いることが可能である。
【００５８】
【発明の効果】
以上説明したように、本発明によれば、波長４００ｎｍ以下、特に３４０ｎｍ〜３８０ｎｍ帯における発光効率を向上させることができる。
【図面の簡単な説明】
【図１】実施形態のＬＥＤの構成図である。
【図２】図１における活性層の構成図である。
【図３】各サンプルの注入電流と光出力（相対値）との関係を示すグラフ図である。
【図４】各サンプルの発光スペクトル説明図である。
【図５】対称バリアのバンド図である。
【図６】非対称バリアのバンド図である。
【符号の説明】
１０ 基板 １２ ＳｉＮ膜、１４ ＧａＮ層、１６ ｕ−ＧａＮ層、１８ ｎ−ＧａＮ層、２０ ｎ−ＳＬＳ層、２２ 活性層、２４ ｐ−ブロック層、２６ ｐ−ＳＬＳ層、２８ ｐ−ＧａＮ層、３０ ｐ型電極、３２ ｎ型電極。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gallium nitride (GaN) -based compound semiconductor device, and more particularly to an improvement in luminous efficiency.
[0002]
[Prior art]
Conventionally, a light emitting device using a nitride semiconductor in a wavelength range of 370 to 550 nm has been put to practical use. In these light-emitting elements, mainly In _x Ga _1-x N (0 <x <1) is used as the light emitting material. In _x Ga _1-x The emission wavelength changes by changing the In composition ratio x in N. Specifically, the emission wavelength increases as x increases. Further, when the In composition ratio x is changed, the luminous efficiency changes together with the emission wavelength. Specifically, when the In composition ratio x becomes too large,
(1) Difference in lattice constant from GaN or AlGaN, which is a layer sandwiching InGaN, increases.
(2) It is necessary to lower the crystal growth temperature in order to grow InGaN having a high In composition.
For example, the crystal quality of InGaN deteriorates, and when the wavelength is longer than 530 nm, the luminous efficiency decreases. The luminous efficiency generally increases in the wavelength range of 400 to 530 nm, but decreases in the wavelength range of 400 nm or less.
[0003]
The decrease in luminous efficiency on the short wavelength side of a wavelength of 400 nm or less is considered to be due to dislocations present in the crystal. The reason why the efficiency of a light-emitting element (LED or the like) having an appropriate In composition ratio and having a wavelength of 400 to 530 nm is high regardless of the dislocation density is due to fluctuation of the In composition in the InGaN layer. That is, if there is a fluctuation in the In composition, light is emitted at a site where the In composition is partially large, so that the injected carriers are captured at the site and cannot reach dislocations, so that the efficiency does not decrease. In order to shorten the emission wavelength, it is necessary to reduce the In composition ratio x as described above, and inevitably the In composition fluctuation also decreases. When the composition fluctuation is small, the carrier is not sufficiently captured, and the carrier reaches the dislocation and the luminous efficiency is reduced.
[0004]
As described above, when the emission wavelength is 400 nm or less, the luminous efficiency largely depends on the dislocation density, and the luminous efficiency decreases due to the presence of the dislocation.
[0005]
[Patent Document 1]
JP-A-2002-289591
[0006]
[Problems to be solved by the invention]
In order to prevent a decrease in luminous efficiency at a wavelength of 400 nm or less, it is necessary to suppress the dislocation density. Conventionally, the dislocation density has been reduced by using, for example, an ELO (Epitaxial Lateral Overgrowth) method or a method of growing a light-emitting layer on a sapphire substrate having a groove formed therein. In these methods, a method such as photolithography is used. As a result, there is a problem that it takes time and effort, and as a result, the cost as a light emitting element increases.
[0007]
An object of the present invention is to obtain a device having excellent luminous efficiency at a short wavelength (especially, a wavelength of 400 nm or less).
[0008]
[Means for Solving the Problems]
The present invention is a gallium nitride-based compound semiconductor device having a gallium nitride-based active layer on a substrate, wherein the gallium nitride-based active layer comprises a first Al _x Ga _1-x An N barrier layer and the first Al _x Ga _1-x In formed on the N barrier layer _y Ga _1-y An N well layer and the In _y Ga _1-y Second Al formed on N well layer _z Ga _1-z An N barrier layer, and the difference between the composition ratio x and the composition ratio z, that is, | xz |, is set to 3% or less. The difference in the Al composition ratio between the barrier layers sandwiching the well layers is 3% or less, in other words, by making the Al composition ratios in the barrier layers sandwiching the well layers substantially the same, the strain in the well layers is alleviated and light emission is performed. Improve efficiency.
[0009]
Specifically, the composition ratio x of the first barrier layer is in the range of 5% ≦ x ≦ 25%, the composition ratio y of the well layer is in the range of 0% <y ≦ 15%, and the composition ratio x of the second barrier layer is The composition ratio z is preferably in the range of 5% ≦ z ≦ 25%. The difference in the Al composition ratio between the first barrier layer and the second barrier layer is maintained within 3%. The composition ratio of the well layer is determined from the emission wavelength. The composition ratio of the first barrier layer and the second barrier layer is defined so that the band gap is larger than that of the well layer, and the lower limit is defined by the carrier confinement effect, and the upper limit is defined by crystallinity and the like. More specifically, the composition ratio x of the first barrier layer is in the range of 10% ≦ x ≦ 15%, the composition ratio y of the well layer is in the range of 0% <y ≦ 15%, and the second barrier layer Is preferably in the range of 10% ≦ z ≦ 15%.
[0010]
Regarding the thickness of each layer of the active layer, for example, the thickness t1 of the first barrier layer is in the range of 5 nm ≦ t1 ≦ 20 nm, and the thickness t2 of the well layer is in the range of 1 nm ≦ t2 ≦ 2.5 nm. The thickness t3 of the two barrier layers is preferably in the range of 5 nm ≦ t3 ≦ 20 nm.
[0011]
In the semiconductor device of the present invention, the semiconductor device further includes an n-type SLS layer below the first barrier layer, wherein the n-type SLS layer is formed of AlαGa _1- An αN layer and a GaN layer are alternately laminated, and the composition ratio α can be in a range of 5% ≦ α ≦ 30%. The n-type SLS layer functions as a cladding layer and injects carriers into the active layer to confine the active layer. The band gap of the n-type SLS layer is set to be larger than the band gap of the active layer.
[0012]
In the semiconductor device of the present invention, a p-type SLS layer is further provided on the second barrier layer, and the p-type SLS layer is formed of AlβGa _1- βN layers and GaN layers are alternately laminated, and the composition ratio β can be in the range of 5% ≦ β ≦ 30%. The p-type SLS layer also functions as a cladding layer, and injects carriers into the active layer to confine it. The band gap of the p-type SLS layer is set to be larger than the band gap of the active layer.
[0013]
In the semiconductor device of the present invention, a p-type AlγGa is further provided between the second barrier layer and the p-type SLS layer. _1- It has a γN block layer, and the composition ratio γ can be in the range of z + 5% ≦ γ. The p-type block layer suppresses electrons from being injected into the p-type layer and recombination, thereby suppressing a decrease in luminous efficiency. The p-type block layer is set to have a band gap larger than the band gap of the second barrier layer in contact with the p-type block layer in the active layer. The function is achieved by having an Al composition that is about% larger. The Al composition of the p-type block layer is set according to the Al composition of the second barrier layer, and is generally set in a range of 10% ≦ γ ≦ 30%.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
<First embodiment>
FIG. 1 shows a configuration of a light emitting element (LED) as a GaN-based compound semiconductor device according to the present embodiment. A light-emitting element is manufactured by growing a plurality of layers on a substrate by MOCVD (metal organic chemical vapor deposition). Specifically, it is manufactured as follows. Although the MOCVD apparatus itself is publicly known, the outline of the apparatus configuration is that a susceptor and a gas introduction pipe are provided in a reaction tube. A substrate is placed on a susceptor, and a raw material gas is supplied while heating the substrate with a heater to cause a reaction on the substrate. The gas introduction part is provided, for example, on two sides of the reaction tube, one is for introducing a raw material gas such as trimethylgallium or silane gas from the side of the substrate, and the other is via a gas-permeable microporous member from the top of the substrate. A mixed gas of hydrogen and nitrogen is supplied.
[0016]
A sapphire c-plane substrate 10 is prepared, set on a susceptor of a normal pressure MOCVD apparatus, and heat-treated at a substrate temperature of 1100 ° C. in a hydrogen atmosphere for 10 minutes. Thereafter, the temperature of the substrate 10 is lowered to 500 ° C., and a monomethylsilane gas and an ammonia gas are flowed for 100 seconds, so that the SiN buffer film 12 is discontinuously formed on the substrate 10. The discontinuous SiN film 12 is for surely reducing dislocations in the layer, but may be omitted in the present embodiment. Next, while maintaining the temperature at 500 ° C., trimethylgallium (TMG) and ammonia gas are flowed to form a 25 nm GaN buffer layer 14. This GaN buffer layer 14 functions as a so-called low-temperature buffer layer. Next, the temperature is raised to 1075 ° C., and trimethylgallium (TMG) and ammonia gas are flown again to form an undoped GaN (u-GaN) layer 16 of 2 μm. Further, a monomethylsilane gas is added to trimethylgallium (TMG) and ammonia gas to form an Si-doped n-GaN layer 18 having a thickness of 1 μm. The monomethylsilane gas is for doping GaN with Si to make it n-type, and the carrier density in the Si-doped n-GaN layer 18 is about 5 × 10 ¹⁸ cm ^-3 It is.
[0017]
Next, while maintaining the temperature of the substrate 10 at 1075 ° C., the Si-doped n-AlαGa _1-a Fifty pairs of N (2.5 nm) / Si-doped n-GaN (2.5 nm) are formed alternately to form an n-SLS (Strained Layer Superlattice) layer 20. In order to form AlGaN, trimethylaluminum (TMA) may be supplied in addition to trimethylgallium (TMG) and ammonia gas (actually, a monomethylsilane gas is supplied to dope Si). The n-SLS layer 20 functions as a cladding layer.
[0018]
Thereafter, the substrate temperature is lowered to about 800 ° C., and undoped Al _x Ga _1-x N / In _y Ga _1-y N / undoped Al _z Ga _1-z N is stacked to form an SQW (single layer quantum well) active layer (light emitting layer) 22. InGaN is formed by supplying trimethylgallium, trimethylindium, and ammonia gas. Undoped In _y Ga _1-y N functions as a well layer, and undoped Al sandwiches the well layer. _x Ga _1-x N and Al _z Ga _1-z N functions as an n-type barrier layer and a p-type barrier layer, respectively.
[0019]
After the formation of the SQW active layer 22, the temperature is increased to 975 ° C. and the Mg doped p-AlγGa having a thickness of 12 nm is formed. _1- The γN block layer 24 is formed. The p-block layer 24 is a layer for reliably suppressing a decrease in luminous efficiency due to injection of electrons into the p-type layer and recombination.
[0020]
After forming the p-block layer 24, Mg-doped p-AlβGa _1- Twenty pairs of β-N (2.5 nm) / Mg-doped p-GaN (2.5 nm) are alternately formed to form the p-SLS layer 26, and further, the p-GaN layer 28 is formed to a thickness of 30 nm. The p-SLS layer 26 also functions as a cladding layer.
[0021]
To summarize the above configuration, the active layer 22 has a pn junction structure in which the n-type clad layer 20 and the p-type clad layer 26 are sandwiched, and the active layer 22 has a quantum well structure in which an InGaN well layer is sandwiched between AlGaN layers.
[0022]
After the LED wafer is prepared as described above, the LED wafer is taken out of the MOCVD apparatus, Ni (10 nm) and Au (10 nm) are sequentially vacuum-deposited and laminated on the surface, and a nitrogen gas atmosphere containing 5% oxygen is used. The heat treatment is performed at 520 ° C. to make the metal film into a p-type transparent electrode 30. After the formation of the p-type transparent electrode 30, a photoresist is applied to the surface, and is etched using the etching mask so as to expose the n-GaN layer 18, and Ti (30 nm) is formed on the exposed n-GaN layer 18, Al (300 nm) is deposited and heat-treated at 450 ° C. for 30 minutes in a nitrogen gas to form an n-type electrode 32.
[0023]
Thereafter, although not shown, a gold pad having a thickness of 500 nm for wire bonding is formed on a part of the p-type electrode 30 and the n-type electrode 32, the back surface of the substrate is polished to 100 μm, and a chip is cut out by scribing. Thus, an LED device is manufactured.
[0024]
Al composition ratio (x, y, z) and film thickness of each layer in active layer 22, Al composition ratio α in n-SLS layer 20, Al composition ratio β in p-SLS layer 26, Al composition in p-block layer 24 Chips were manufactured with various ratios γ, and the manufactured chips were placed in an integrating sphere, current was injected, and the total light output and emission wavelength emitted from the chips were measured. As a result, it has been found that when the emission peak wavelength is 400 nm or less, particularly in the 340 nm to 380 nm band, an optical output of 1 mW or more can be obtained at the composition ratio and film thickness shown in Table 1 below.
[0025]
[Table 1]

[0026]
FIG. 2 shows a configuration in which only the active layer 22 is extracted from FIG. The active layer 22 is made of Al as described above. _x Ga _1-x N layer (n-side barrier layer 22a), In _y Ga _1-y N layer (well layer 22b), Al _z Ga _1-z It is composed of an N layer (p-side barrier layer 22c). As shown in Table 1, the composition ratios x, y, and z are
5% ≦ x ≦ 25%
0% <y ≦ 15%
5% ≦ z ≦ 25% (1)
When the above condition is satisfied, a light emission output of 1 mW or more can be obtained. Regarding the barrier layers 22a and 22c sandwiching the well layer 22b, the composition ratios x and z are preferably substantially equal, and specifically,
| X−z | ≦ 3% (2)
It is desirable that
[0027]
Table 2 shows the emission intensity when the Al composition ratio y of the well layer 22b is fixed and the Al composition ratios x and z of the n-side barrier layer 22a and the p-side barrier layer 22c are changed.
[0028]
[Table 2]

[0029]
In Table 2, in the sample (a), when the n-side barrier layer 22a and the p-side barrier layer 22c are both 7% symmetric, the sample (b) has the n-side barrier layer 22a of 7% and the p-side barrier layer 22c of 12%. %, The sample (c) is a case where both the n-side barrier layer 22a and the p-side barrier layer 22c are symmetrical with 12%. The light output is a relative value with the light output of the sample (c) when 20 mA and 100 mA are injected as the reference value 1. FIG. 3 shows the light output of the samples (a), (b), and (c) when the injection current is changed, and FIG. 4 shows the emission spectrum of the sample. The emission wavelength of each sample is in the range of 370 nm ± 5 nm, although there is some variation in the wafer plane.
[0030]
As can be seen from Table 2 and FIG. 3, the emission output greatly changes by changing the Al composition ratio of the n-side barrier layer 22a and the p-side barrier layer 22c. It is effective to make the Al composition ratios x and z of the n-side barrier layer 22a and the p-side barrier layer 22c substantially the same, and set these composition ratios to a certain value or more.
[0031]
That is, comparing the sample (a) with the sample (b), the sample (a) is higher when the injection current is smaller, though the Al composition ratio of the p-side barrier layer 22c is smaller than that of the sample (b). Light output is obtained. Generally, it is considered that increasing the Al composition ratio increases the band gap and increases the effect of confining carriers. However, the result of the present embodiment cannot be explained by this idea. On the other hand, in sample (c) in which the Al composition ratio is larger than sample (a), the light output is increased, and it is not considered that the deterioration of the crystal due to the increase in the Al composition ratio is the cause. Therefore, the results in Table 2 and FIG. 3 are considered to be due to crystal distortion. Since AlGaN, which is a material of the barrier layer, and InGaN, which is a material of the well layer, have different lattice constants, when these heterojunctions are formed on the GaN layer, crystal distortion occurs in both. In particular, when these layers are thin, the crystal is elastically distorted, so that no dislocation occurs. Also, when in-plane strain is applied to AlGaN and InGaN grown so that the c-axis is perpendicular to the substrate surface, an electric field is generated perpendicular to the substrate surface due to the piezoelectricity of these materials. This vertical electric field forms a slope in the band structure of the active layer 22 and separates the electron-hole pairs injected into the active layer 22 to lower the luminous efficiency.
[0032]
5 and 6 show band diagrams of the active layer 22. FIG. FIG. 5 is a band diagram when the Al composition ratio is symmetric (substantially the same) between the n-side barrier layer 22a and the p-side barrier layer 22c as in samples (a) and (c), and FIG. FIG. 4B is a band diagram when the Al composition ratio is asymmetric (substantially not the same) between the n-side barrier layer 22a and the p-side barrier layer 22c as in FIG. In both figures, (A) is a predicted band diagram of a conduction band, and (B) is a band diagram of a valence band.
[0033]
As shown in FIG. 6, a larger strain is applied to the InGaN well layer 22b sandwiched between the asymmetric barriers than in the case of the symmetric barrier shown in FIG. 5, and as a result, a larger electric field is applied and electrons and electrons are applied. The hole pairs are spatially separated, causing a decrease in luminous efficiency. When the current is increased, the density of carriers injected into the well layer 22b increases, and the electric charge cancels out the distorted electric field (Coulomb screening effect). Therefore, in the case of the asymmetric structure as in the sample (b), the luminous efficiency sharply increases when the current is increased, and when the current exceeds 50 mA, the luminous efficiency is increased by the higher carrier confinement effect of the p-side barrier layer 22c. It is thought that it will exceed. On the other hand, in the sample (c), the luminous efficiency is higher than in the samples (a) and (b) due to the symmetric barrier and the high confinement effect.
[0034]
As described above, the Al composition of the n-side barrier layer 22a and the p-side barrier layer 22c are made substantially the same to form a symmetric barrier, thereby suppressing distortion in the well layer 22b and improving luminous efficiency at a low injection current. Can be done. Further, the Al composition ratio of the n-side barrier layer 22a and the p-side barrier layer 22c affects the carrier confinement effect at the time of high injection current, and when the Al composition ratio is too small, the luminous efficiency at the time of high injection current decreases. . From the above, it can be seen that the conditions (1) and (2) are effective for improving the luminous efficiency.
[0035]
The more preferable composition ratio of the active layer 22 is as follows.
[0036]
10% ≦ x ≦ 15%
0% <y ≦ 15%
10% ≦ z ≦ 15% (3)
The lower limits of x and y take into account the carrier confinement effect at high injection current, and the upper limits take into account crystal degradation.
[0037]
As shown in Table 1, the n-side barrier layer 22a has a thickness of 5 nm to 20 nm, the well layer 22b has a thickness of 1 nm to 2.5 nm, and the p-side barrier layer 22c has a thickness of 5 nm. It has been confirmed that a desired emission output can be obtained if the thickness is not less than 20 nm.
[0038]
Further, the n-SLS layer 20 and the p-SLS layer 26 have a band gap larger than that of the active layer 22 and function as a cladding layer for injecting carriers into the active layer 22, so that the Al composition ratio is determined. When the active layer 22 satisfies the above conditions (1) and (2), the conditions to be satisfied by the n-SLS layer 20 and the p-SLS layer 26 are as follows.
[0039]
5% ≦ α ≦ 30%
5% ≦ β ≦ 30% (4)
Further, regarding the p-block layer 24, the well layer 22b and the p-side barrier layer 22c of the active layer 22 are used to suppress a decrease in luminous efficiency due to injection of electrons into the p-type layer and recombination. Are also set to increase the band gap. That is, the condition that the p-block layer 24 must satisfy is
z + 5% ≦ γ (5)
And specifically,
10% ≦ γ ≦ 30% (6)
It is.
[0040]
The composition ratio considered to be the best in the present embodiment is as follows.
[0041]
n-SLS layer 20:
n-Al _0.18 Ga _0.82 N / n-GaN
Active layer (light emitting layer) 22:
Al _0.12 Ga _0.88 N / In _0.13 Ga _0.87 N / Al _0.12 Ga _0.88 N
p-block layer 24:
Al _0.18 Ga _0.82 N
p-SLS layer 26
p-Al _0.18 Ga _0.82 N / p-GaN
Of course, these compositions are examples, and those skilled in the art can select any composition within the above range. Further, in the present embodiment, the structure is basically n-type cladding layer 20 / active layer 22 / p-type blocking layer 24 / p-type cladding layer 26. For example, p-type blocking layer 24 is omitted or active layer 22 is formed. It is also possible to add further functional layers between the and the cladding layer, and these are all modifications of the present invention.
[0042]
In the present embodiment, the SQW structure in which the well layer 22b is sandwiched between the barrier layers 22a and 22c is used as the active layer 22, but the configuration of the n-side barrier layer 22a / the well layer 22b / p-side barrier layer 22c is laminated in a plurality of periods. It is also possible to use the MQW (multilayer quantum well) structure described above. Even when MQW is used, the luminous efficiency can be improved particularly at a low injection current by suppressing the difference in the Al composition ratio of the barrier layers sandwiching the well layer to 3% or less.
[0043]
As described above, since the LED in the present embodiment has a high luminous efficiency at a wavelength of 400 nm or less, various products can be manufactured by exclusively utilizing this characteristic. Hereinafter, some examples of devices using the LED or the light emitting element shown in FIG. 1 as a light source will be described.
[0044]
<Second embodiment>
Commercially available black pens (highlighters) (made by Shinloich) are invisible even when characters or figures are drawn under visible illumination, but the characters or figures drawn appear when irradiated with ultraviolet light. Colored black pens (colored graphics appear when irradiated with ultraviolet light) are also commercially available, but in order to reproduce color, the wavelength of the ultraviolet light to be irradiated must be 400 nm or less, more precisely 380 nm or less. Conventionally, a light source such as a fluorescent black light or a mercury lamp is used. However, there are drawbacks in that the light source is large, consumes large power, and requires a large power supply.
[0045]
Therefore, if the light emitting device (LED) shown in FIG. 1 is used as a light source for graphic reproduction, it can be small and can be driven by a battery. A figure drawn with a black pen was irradiated with LEDs having peak wavelengths of 400 nm, 385 nm and 372 nm to try to reproduce the figure. The irradiation light intensity is about 5 mW (400 nm), 3 mW (385 nm), and 1 mW (372 nm).
[0046]
In the case of the 400 nm LED, although a figure appeared, the color was not reproduced, and the intensity of the fluorescence was at a very low level that was barely visible. When illuminated with a 385 nm LED, the fluorescence intensity was strong enough to clearly see the shape of the figure, but the color was not reproduced. In particular, the reproducibility of the red color was poor. On the other hand, in the case of the LED with the wavelength of 372 nm, the fluorescence was strong enough to be seen without any problem even in a bright room, and the three primary colors could be faithfully reproduced even though the irradiation intensity was as low as 1 mW.
[0047]
From these, it was confirmed that the LED in the wavelength band of 365 to 380 nm is very suitable as a light source for reproducing a figure drawn with a commercially available black pen (fluorescent pen). A system for drawing invisible characters and figures that can be easily reproduced by incorporating the LED of this embodiment together with a battery in a key holder, a black pen, an eraser, and other products is obtained.
[0048]
<Third embodiment>
In this embodiment, the light from the LED was irradiated on the skin of the human body for a short time, and the effect was examined. The skin was irradiated with LED light having peak wavelengths of 400 nm (5 mW), 385 nm (3 mW), and 372 nm (1 mW) for 10 minutes, respectively, to examine changes in the skin (so-called sunburn). As a result, almost no effect was observed when the peak wavelength was 400 nm (5 mW), whereas a slight change was observed when the peak wavelength was 385 nm (3 mW). On the other hand, in the case of 372 nm (1 mW), a clear trace was seen. This indicates that the LED in the wavelength band of 365 to 380 nm causes sunburn on the human body. A tanning device was manufactured using this LED as a light source. An apparatus for tanning only the spot having a diameter of 5 mm and an apparatus for arranging the LED on a straight line having a length of 3 cm to tan on the striatum were manufactured, and an experiment was conducted. Both devices were tanned by irradiation for 10 minutes. In addition, skin irradiation was observed when irradiated for 30 minutes or more.
[0049]
Conventionally, tanning equipment uses ultraviolet lamps, so it was suitable for applications with a large irradiation area, but it was not possible to create tanning in only a small area. However, in the tanning device of the present embodiment, it is possible to arbitrarily create a tan such as a point or a line.
[0050]
<Fourth embodiment>
The skin coated with a commercially available UV-cut cosmetic (SPF50 + PA ++) was irradiated for 10 minutes with the tanning device of the third embodiment in which an LED having a peak wavelength of 372 nm (1 mW) was incorporated in the light source. As a result, it was confirmed that the degree of sunburn was extremely small as compared with the case where the UV cut cosmetic was not applied. Thus, the LED of the present embodiment can be used as an apparatus for evaluating the performance of UV cut cosmetics.
[0051]
Conventionally, this type of inspection device is large and requires a large skin surface to examine its effect. As described in the above embodiment, the inspection apparatus according to the present embodiment can make a tan on an arbitrary shape or site such as a point or a line. It is also possible to examine the irradiation effect over a long period of time.
[0052]
<Fifth embodiment>
Luminescent materials are used for signs such as clock faces and evacuation guidance. This utilizes a mechanism in which, when light is applied to a luminous agent, characters are read even in darkness by utilizing the fact that fluorescence continues even if the light is turned off. In recent years, the luminous time has become longer and three primary colors can be produced. For example, a short afterglow type in which copper is bonded to zinc sulfide and a long afterglow type in which rare earth metal is bonded to strontium aluminate are known. The sensitivity of such a luminous agent is generally at a wavelength of 400 nm or less. Therefore, by combining the luminous agent and the LED of this embodiment, a display device with extremely low power consumption can be manufactured by repeating the operation of irradiating light for a short time and extinguishing the light. Further, an emergency display device in which the display is not erased (non-volatile) even when the power is turned off can be realized.
[0053]
A display device was manufactured by combining LEDs having peak wavelengths of 400 nm (5 mW), 385 nm (3 mW), and 372 nm (1 mW) with a luminous agent of three primary colors. The phosphorescent agent was processed into a plate shape, and the light of the LED of the embodiment was irradiated from the back surface to observe the light emission from the front surface. The cycle of irradiating for 10 minutes and turning off the irradiation for a predetermined time was repeated. Even after the irradiation was stopped for about 30 minutes, light emission from the luminous agent was confirmed in a room having a brightness as low as an office. In addition, light emission from the luminous agent was confirmed even in the dark for about one hour. Similar effects were obtained at all wavelengths, but the afterglow was strongest when a peak wavelength of 400 nm (5 mW) was used as the light source.
[0054]
As described above, with the display device using the LED in the wavelength band of 365 to 400 nm and the luminous agent, the power consumption can be significantly reduced as compared with the conventional display device.
[0055]
Furthermore, color reproducibility was also observed. LEDs with peak wavelengths of 400 nm (5 mW) and 385 nm (3 mW) appear blue to violet to the naked eye. Therefore, if red light is emitted with a luminous agent, the two will be mixed and pure red cannot be reproduced. The same is true for green. On the other hand, since an LED having a peak wavelength of 372 nm (1 mW) is hardly visible to the naked eye, the three primary colors can be faithfully reproduced. Therefore, a display device using an LED in a wavelength band of 365 to 380 nm as a light source and using a light storage agent can reproduce low power consumption and full color.
[0056]
<Sixth embodiment>
The compound eyes of insects such as moths have a peak sensitivity at a wavelength of 360 nm. Utilizing this property, insect control devices using ultraviolet lamps are commercially available. An ultraviolet lamp was attached to the street and an insect control device was installed around the street. Ultraviolet lamps generally appear bright because they also emit visible light. In addition, there is a problem that power consumption is large. The LED of the embodiment was used as a light source for collecting insects. The peak wavelength is 372 nm. An LED was installed in the dark to check the status of insect gathering. At the same time, a 2 W mercury lamp was installed at another location for comparison. In order to save the power consumption of the LED and increase the emission peak intensity, pulse driving was performed at a peak current of 200 mA, a peak output of about 10 mW, a pulse width of 10 mS, and a repetition frequency of 10 Hz (average output of 1 mW). Light output was observed to attract more insects to the LED despite the smaller LED. The mercury lamp appeared blue to purple to the naked eye, but the LED was hardly visible to the naked eye. From this, it is understood that an LED in a wavelength band of 365 to 380 nm can be used as a light source for collecting insects.
[0057]
Therefore, a lamp of a commercially available insect control apparatus was replaced with an LED to manufacture the apparatus. Using 200 LEDs having a wavelength of 372 nm, pulse driving was performed in the same manner as in the experiment described above to operate. As a result, the same level of insects as before the remodeling could be eliminated overnight. The insect control apparatus using the LED of the present embodiment as a light source has advantages in that power consumption is small, and since the LED is small, the degree of freedom in the layout of the light source is increased. Furthermore, since it is almost invisible to the naked eye, it can be used in environments where lighting is disliked.
[0058]
【The invention's effect】
As described above, according to the present invention, it is possible to improve the luminous efficiency in a wavelength of 400 nm or less, particularly in a 340 nm to 380 nm band.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an LED according to an embodiment.
FIG. 2 is a configuration diagram of an active layer in FIG.
FIG. 3 is a graph showing a relationship between an injection current and a light output (relative value) of each sample.
FIG. 4 is an explanatory diagram of an emission spectrum of each sample.
FIG. 5 is a band diagram of a symmetric barrier.
FIG. 6 is a band diagram of an asymmetric barrier.
[Explanation of symbols]
10 substrate 12 SiN film, 14 GaN layer, 16 u-GaN layer, 18 n-GaN layer, 20 n-SLS layer, 22 active layer, 24 p-block layer, 26 p-SLS layer, 28 p-GaN layer, 30 p-type electrode, 32 n-type electrode.

Claims (8)

A gallium nitride-based compound semiconductor device having a gallium nitride-based active layer on a substrate,
The gallium nitride based active layer,
A first _Al x _{Ga 1-x} N barrier layer,
And _In y _{Ga 1-y} N well layer formed on the first _Al x _{Ga 1-x} N barrier layer,
A second _Al z _{Ga 1-z} N barrier layer formed on said _In y _{Ga 1-y} N well layer,
Has,
A gallium nitride-based compound semiconductor device, wherein the difference | xz | between the composition ratio x and the composition ratio z is set to 3% or less. The device of claim 1,
The composition ratio x is in the range of 5% ≦ x ≦ 25%, the composition ratio y is in the range of 0% <y ≦ 15%, and the composition ratio z is in the range of 5% ≦ z ≦ 25%. A gallium nitride-based compound semiconductor device. The device of claim 1,
The composition ratio x is in the range of 10% ≦ x ≦ 15%, the composition ratio y is in the range of 0% <y ≦ 15%, and the composition ratio z is in the range of 10% ≦ z ≦ 15%. A gallium nitride-based compound semiconductor device. The device of claim 1,
The first _Al x _{Ga 1-x} N thickness t1 of the barrier layer is in the range of 5 nm ≦ t1 ≦ 20 nm, the _In y _{Ga 1-y} N thickness t2 of the well layer is 1 nm ≦ t2 ≦ 2.5 nm of the range, the second _Al z _{Ga 1-z} N barrier layer gallium nitride-based compound semiconductor device, wherein the thickness t3 is in the range of 5 nm ≦ t3 ≦ 20 nm of. The device of claim 1, further comprising:
The first _Al x _{Ga 1-x} N has a n-type SLS layer formed under the barrier layer, the n-type SLS layer is constructed by alternately laminating AlαGa _1- αN layer and the GaN layer, The gallium nitride-based compound semiconductor device, wherein the composition ratio α is in the range of 5% ≦ α ≦ 30%. The device according to any one of claims 1 and 5, further comprising:
A p-type SLS layer formed on the second Al _z Ga _1-z N barrier layer, wherein the p-type SLS layer is formed by alternately stacking an AlβGa _1- βN layer and a GaN layer; The gallium nitride-based compound semiconductor device, wherein the composition ratio β is in the range of 5% ≦ β ≦ 30%. The apparatus of claim 6, further comprising:
Has a p-type AlγGa _1- γN blocking layer formed between the second _Al z _{Ga 1-z} N barrier layer and the p-type SLS layer, it is gamma compositional ratio in the range of z + 5% ≦ γ A gallium nitride-based compound semiconductor device, comprising: The apparatus of claim 6, further comprising:
The second _Al z _{Ga 1-z} N barrier layer and has p-type AlγGa _1- γN blocking layer formed between the p-type SLS layer, the range of 10% ≦ γ ≦ 30% γ composition ratio A gallium nitride-based compound semiconductor device, characterized in that:

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