JP4287702B2 - Oxide semiconductor light emitting device - Google Patents

Description

【００５９】
上記表１の結果より、端面保護を行わない場合（比較例５）や硫黄処理のみを行った場合（比較例４）に比べ、前面および後面をＭｇＯを含む多層膜で端面保護した場合（本参考例１や比較例１）の方が発振閾値電流が低く、素子寿命が向上することが判る。
【００６０】
また、本参考例１と比較例３との比較より、酸化物多層膜は片端面のみより両端面に形成した方が保護効果が強いことが判る。つまり、上記前面と後面との一方に、ＭｇＯを含む多層膜で端面保護を行っても、前面および後面に端面保護を行わない場合よりも、素子寿命を延ばすことができるが、前面と後面との両方に、ＭｇＯを含む多層膜で端面保護を行えば、素子寿命を更に延ばすことが出来る。また、上記前面と後面との両方に、ＭｇＯを含む多層膜で端面保護を行うことにより、閾値電流の低減効果も得ることが出来る。
【００６１】
そして、本参考例１と比較例１との比較より、保護膜は金属酸化物の積層によって構成された方が特性改善効果が高いことが判る。
【００６２】
更に、本参考例１と比較例２との結果より、酸化物層がＺｎＯ系半導体レーザ素子端面と接した方が特性改善効果が高いことが判る。つまり、上記半導体レーザ素子の光出射端面や光反射端面に、多層膜が含む金属酸化物層を接触させることにより、特性改善効果を高めることが出来る。
【００６３】
以上の結果より、ＺｎＯ系半導体レーザ素子の光出射端面，光反射端面のうちの少なくとも一方の上に、屈折率が異なる複数の金属酸化物を含む多層膜が形成することにより、素子寿命が長くなって信頼性が向上することがわかる。この理由は、上記金属酸化物はＺｎＯ系半導体と同じ酸化物であるための親和性が良く密着性に優れ、特に複数の金属酸化物層より成る多層膜を光出射端面，光反射端面上に形成することにより、光出射端面，光反射端面を還元雰囲気から保護する効果が高くなるためと考えられる。
【００６４】
上記金属酸化物の結晶が粒界を含んでいると、高い光エネルギに晒された時に破壊されやすいため、非晶質または単結晶である金属酸化物を用いることが好ましい。また、上記光出射端面，光反射端面上に形成する多層膜が非晶質または単結晶薄膜であればより好ましい。
【００６５】
上記酸化物多層膜を構成する金属としては、Ｍｇ、Ｓｃ、Ｙ、Ｔｉ、Ｚｒ、Ｈｆ、Ｃｅ、Ｖ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｒｅ、Ａｌ、Ｇａ、ＳｉおよびＧｅなどが好ましい。これらの金属の金属イオンの多くは電子軌道が異方性を持たないので、上記金属の酸化物は非晶質または単結晶となりやすい。
【００６６】
本参考例１において、ＭｇＯ層およびＳｉＯ₂層は、それぞれ１層当りの層厚が略λ／（４ｎ）（λ:発振波長、ｎ:酸化物層の屈折率）となるように作製している。これにより、上記酸化物多層膜１１２Ａ，１１２Ｂでは、入射光に対する各境界（各層間の境界）からの反射光の位相が全て揃い、高い反射率が得られるので好ましい。
【００６７】
なお、上記酸化物多層膜１１２Ａ，１１２Ｂでの光反射は、入射光が屈折率の高い酸化物層から屈折率の低い酸化物層への境界では位相が変化しないのに対し、その逆では位相がπだけ変化する。
【００６８】
（実施形態）
本実施形態のＺｎＯ系半導体レーザ素子は、厚さ５５ｎｍのＭｇ_0.3Ｚｎ_0.7Ｏ層と厚さ４０ｎｍのＴｉＯ₂層との交互積層で構成した酸化物多層膜を、上記酸化物多層膜１１２Ａ，１１２Ｂの代わりに用いた他は、上記参考例１と同様に作製した。
【００６９】
本実施形態の酸化物多層膜は、光出射端面および光反射端面にＭｇ_0.3Ｚｎ_0.7Ｏ層が接するように形成されている。また、上記Ｍｇ_0.3Ｚｎ_0.7Ｏ層とＴｉＯ₂層との層数は、波長４１０ｎｍの光に対する酸化物多層膜の反射率が２０％となるように調整している。
【００７０】
本実施形態の半導体レーザ素子に電流を流したところ、光出射端面から波長４１０ｎｍの青色発振光が得られ、発振閾値電流と素子寿命とは、上記参考例１と同様であった。
【００７１】
比較例６として、光出射端面および光反射端面にＴｉＯ₂層が接するように酸化物多層膜を形成した他は、本実施形態と同様に半導体レーザ素子を作製した。この比較例２の半導体レーザ素子は、発振閾値電流が本実施形態よりも２０％増大し、素子寿命が３０％短くなった。
【００７２】
比較例６の半導体レーザ素子では、ＴｉＯ₂がＭｇ_0.3Ｚｎ_0.7Ｏに比べてバンドギャップエネルギが小さいため、ＺｎＯ半導体からの漏れ電流によって特性が悪化したものと考えられる。したがって、多層膜を構成する金属酸化物のうち、バンドギャップエネルギの最も大きい金属酸化物がＺｎＯ半導体と接していることが好ましい。つまり、上記酸化物多層膜が含む複数の金属酸化物のうち、最もバンドギャップエネルギが大きい金属酸化物が光出射端面，光反射端面に接することが好ましい。
【００７３】
（参考例２）
本参考例２のＺｎＯ系半導体レーザ素子は、厚さ３５ｎｍのＣａＨｆＯ₃層と厚さ５０ｎｍのＣｅＯ層との交互積層で構成した酸化物多層膜を、上記酸化物多層膜１１２Ａ，１１２Ｂの代わりに用いた他は、上記参考例１と同様に作製した。
【００７４】
本参考例２の半導体レーザ素子に電流を流したところ、光出射端面から波長４１０ｎｍの青色発振光が得られ、発振閾値電流と素子寿命とは上記参考例１と同様であった。
【００７５】
図３（ａ）に、αβＯ₃なる組成を有するペロブスカイト酸化物の表面構造を示す。また、図３（ｂ）に、ＺｎＯの表面構造を示す。
【００７６】
図３（ａ），（ｂ）に示すように、ペロブスカイト構造の（１１１）面は、ＺｎＯ系半導体などのウルツ鉱結晶構造の（０００１）面と類似の表面構造を有する。このため、ペロブスカイトは、ＺｎＯ系半導体との親和性に優れ、ＺｎＯ界面に積層した際の結晶欠陥が極めて小さい。
【００７７】
このようなペロブスカイトのαβＯ₃は、次の（ａ）〜（ｃ）の条件のうちの何れか１つを満たすことが好ましい。
（ａ） 上記αの元素はＬｉ、ＮａおよびＫより選択された１つ以上を含み、且つ、上記βの元素はＴａまたはＮｂを含む。
（ｂ） 上記αの元素はＣｄ、Ｃａ、Ｓｒ、ＢａおよびＢｉより選択された１つ以上を含み、且つ、上記βの元素はＴｉ、Ｚｒ、ＨｆおよびＳｎより選択された１種つ以上を含む。
（ｃ） 上記αの元素はＢｉ、希土類およびアルカリ土類より選択された１つ以上を含み、且つ、上記βの元素はＩｎ、Ａｌ、ＧａおよびＳｃより選択された１つ以上を含む。
【００７８】
特に、上記αβＯ₃は、ＫＮｂＯ₃、ＫＴａＯ₃、ＢａＴｉＯ₃、ＣａＳｎＯ₃、ＣａＺｒＯ₃、ＣａＨｆＯ₃、ＣｄＳｎＯ₃、ＳｒＨｆＯ₃、ＳｒＳｎＯ₃、ＳｒＴｉＯ₃およびＹＳｃＯ₃のいずれか１つであれば、六角形の格子形状がＺｎＯ（０００１）面と整合し易くなり、界面欠陥の極めて少ない高品質な多層反射膜を形成出来る。
【００７９】
（参考例３）
本参考例３のＺｎＯ系半導体レーザ素子では、ＭｇＯ層とＳｉＯ₂層との層数を調整することにより、光出射端面上の酸化物多層膜の反射率を１０％とし、光反射端面上の酸化物多層膜の反射率を８０％とした他は、上記参考例１と同様にして本発明の酸化物半導体発光素子を作製した。
【００８０】
本参考例３の半導体レーザ素子に電流を流したところ、光出射端面から波長４１０ｎｍの青色発振光が得られた。また、上記半導体レーザ素子は、発振閾値電流が上記参考例１に比べ２０％低減し、素子寿命が上記参考例１に比べ２０％長くなった。
【００８１】
本参考例３で示したように、光反射端面上の酸化物多層膜の反射率を高くする一方、光出射端面上の酸化物多層膜の反射率を低くすることにより、光出射効率を向上させることが出来る。
【００８２】
本発明の保護膜の一例としての酸化物多層膜は、ＺｎＯ系半導体レーザ素子を還元雰囲気から保護するのみならず、積層数によって反射率を制御することが出来、反射損失を低減して発振閾値電流を下げ、信頼性に優れた半導体レーザ素子を作製出来る。
【００８３】
上記光出射端面上の酸化物多層膜の反射率が５％〜３５％であれば、十分な光出力を確保出来る。また、上記光反射端面上の酸化物多層膜の反射率が７０％以上であれば、十分な反射率を確保出来る。但し、半導体レーザ素子の光出力をモニタするために光反射端面からの光出力を受光素子で検出する場合には、光反射端面上の酸化物多層膜の反射率を９５％以下にすると好ましい。
【００８４】
（参考例４）
本参考例４では、面発光型のＺｎＯ系半導体レーザ素子に本発明を適用した一例について説明する。
【００８５】
図４に、本参考例４の面発光型半導体レーザ素子の模式斜視図を示す。この半導体レーザ素子は基板側から発振光を取り出す構造になっており、図４に示された構造は積層順とは上下が逆になっている。つまり、図４において、ｎ型ＺｎＯ単結晶基板２０１下の複数の成長層では、図中上側の成長層が図中下側の成長層よりも先に積層されたものである。
【００８６】
以下では、基板上に上記複数の成長層が形成されているものとして説明を行う。つまり、以下の説明の上下は図４における上下とは逆となる。
【００８７】
上記面発光型半導体レーザ素子は、亜鉛面を主面としたｎ型ＺｎＯ単結晶基板２０１上に、厚さ２０ｎｍのＭｇ_0.15Ｚｎ_0.85Ｏ第１エッチングストップ層２０２、Ｇａドーピング濃度が１×１０¹⁸ｃｍ^-3で厚さ０．１μｍのｎ型ＺｎＯバッファ層２０３、Ｇａドーピング濃度が１×１０¹⁸ｃｍ^-3で厚さ１．０μｍのｎ型Ｍｇ_0.1Ｚｎ_0.9Ｏクラッド層２０４、ノンドープ量子井戸活性層２０５、Ｎドーピング濃度が５×１０¹⁸ｃｍ^-3で厚さ０．１μｍのｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第１クラッド層２０６、厚さ２０ｎｍのＭｇ_0.15Ｚｎ_0.85Ｏ第２エッチングストップ層２０７、Ｎドーピング濃度が５×１０¹⁹ｃｍ^-3で厚さ１．１μｍのｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層２０８、Ｎドーピング濃度が１×１０²⁰ｃｍ^-3で厚さ０．５μｍのｐ型ＺｎＯコンタクト層２０９がこの順で積層されている。
【００８８】
本参考例４では、ｎ型ＺｎＯ単結晶基板２０１が基板の一例に、ｎ型Ｍｇ_0.1Ｚｎ_0.9Ｏクラッド層２０４が第１導電型クラッド層の一例に、Ｍｇ_0.15Ｚｎ_0.85Ｏ第１エッチングストップ層２０２のｎ型ＺｎＯ単結晶基板２０１側の表面が光出射端面の一例に、量子井戸活性層２０５が活性層の一例に、ｐ型ＺｎＯコンタクト層２０９が第２導電型コンタクト層の一例にそれぞれ相当している。また、上記ｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第１クラッド層２０６とｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層２０８が第２導電型クラッド層の一例を構成している。
【００８９】
上記量子井戸活性層２０５は、厚さ５ｎｍのＺｎＯ障壁層２層と、厚さ６ｎｍのＣｄ_0.05Ｚｎ_0.95Ｏ井戸層３層とが交互に積層されている。上記ＺｎＯ障壁層は２層ある一方、Ｃｄ_0.05Ｚｎ_0.95Ｏ井戸層が３層ある。
【００９０】
上記ｐ型ＺｎＯコンタクト層２０９およびｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層２０８は円柱状にエッチング加工され、側面がｎ型Ｍｇ_0.3Ｚｎ_0.7Ｏ電流ブロック層２１０によって埋め込まれている。つまり、上記ｐ型ＺｎＯコンタクト層２０９およびｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層２０８は、ｎ型ＺｎＯ単結晶基板２０１の表面と略平行な方向においてｎ型Ｍｇ_0.3Ｚｎ_0.7Ｏ電流ブロック層２１０で取り囲まれている。このｎ型Ｍｇ_0.3Ｚｎ_0.7Ｏ電流ブロック層２１０は、Ｇａが１×１０¹⁸ｃｍ^-3の濃度でドーピングされている。
【００９１】
上記ｎ型ＺｎＯ基板２０１下にはｎ型オーミック電極２１１が形成されている。このｎ型オーミック電極２１１およびｎ型ＺｎＯ基板２０１では、ｐ型ＺｎＯコンタクト層２０９およびｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層２１８直下に対応する部分がエッチングで除去されて開口部が形成されている。このエッチングにより露出したＭｇ_0.15Ｚｎ_0.85Ｏ第１エッチングストップ層２０７下に、保護膜の一例としての多層反射膜２１２を形成している。この多層反射膜２１２は、金属酸化物の一例としてのＣａＺｒＯ₃と、金属酸化物の一例としてのＡｌ₂Ｏ₃との交互積層で構成されている。また、上記多層反射膜２１２は、波長４００ｎｍの発光に対する反射率が２０％となるように、ＣａＺｒＯ₃およびＡｌ₂Ｏ₃の層数が調整されている。
【００９２】
上記ｐ型ＺｎＯコンタクト層２０９上には、ｐ型オーミック電極２１３、Ａｇ高反射電極２１４およびＡｕパッド電極２１５が順次形成されている。上記Ａｇ高反射膜２１４は波長２００ｎｍの発光に対する反射率が９５％である。
【００９３】
本参考例４の半導体レーザ素子に電流を流したところ、開口部から波長４００ｎｍの青色発振光が得られた。
【００９４】
比較例７として、多層反射膜２１２を形成しない他は、本参考例４と同様にして面発光型半導体レーザ素子を作製した。この比較例７の面発光型半導体レーザ素子は、本参考例４に比べて発振閾値電流が１０％増大し、素子寿命が１／１０になった。
【００９５】
比較例８として、多層反射膜２１２をＳｉ₃Ｎ₄とＡｌＮとの交互積層で構成した他は、本参考例４と同様にして面発光型半導体レーザ素子を作製した。この比較例８の面発光型半導体レーザ素子は、発振閾値電流は本参考例４と略同じであったが、素子寿命が本参考例４よりも２０％短かくなった。
【００９６】
本参考例４の結果より、面発光型のＺｎＯ系半導体レーザ素子に対しても本発明は効果を有し、光出射端面に金属酸化物を含む多層膜が形成されることにより、素子寿命が長くなって信頼性が向上することがわかる。
【００９７】
上記実施形態および参考例１〜３で述べた好ましい条件は、本参考例４に用いてもよいのは言うまでもない。
【００９８】
また、本参考例４では、Ａｇ高反射電極２１４が光反射端面の一例に相当している。
【００９９】
上記実施形態および参考例１〜４の半導体レーザ素子は、基板上に、少なくとも、ｎ型クラッド層、活性層、ｐ型クラッド層およびｐ型コンタクト層が順次積層される構造を有していたが、基板上に、少なくとも、ｐ型クラッド層、活性層、ｎ型クラッド層およびｎ型コンタクト層が順次積層される構造を有してもよい。
【０１００】
【発明の効果】
以上より明らかなように、本発明の酸化物半導体発光素子は、光共振器が有する光出射端面，光反射端面のうちの少なくとも一方の上に、屈折率の異なる複数の金属酸化物を含むと共に、複数の層から成る保護膜が形成されているので、保護膜とＺｎＯ系半導体との親和性が良いと共に、保護膜において還元雰囲気からの保護効果が高い。したがって、素子寿命を延ばすことが出来、且つ、発振閾値電流を低減出来る。つまり、長時間の駆動に対して信頼性に優れた酸化物半導体発光素子を作製出来る。
【図面の簡単な説明】
【図１】 図１は本発明の参考例１のＺｎＯ系半導体レーザ素子の模式斜視図である。
【図２】 図２は上記参考例１のＺｎＯ系半導体レーザ素子の模式側面図である。
【図３】 図３（ａ）はペロブスカイト酸化物の表面構造を表す図であり、図３（ｂ）はＺｎＯの表面構造を表す図である。
【図４】 図４は本発明の参考例４の面発光型半導体レーザ素子の模式斜視図である。
【符号の説明】
１０１，２０１ ｎ型ＺｎＯ単結晶基板
１０３，２０４ ｎ型Ｍｇ_0.1Ｚｎ_0.9Ｏクラッド層
１０５，２０５ 量子井戸活性層
１０７ ｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏクラッド層１０７
１０８，２０９ ｐ型ＺｎＯコンタクト層
１１３ 光出射端面
１１４ 光反射端面
２０６ ｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第１クラッド層
２０８ ｐ型Ｍｇ_0.1Ｚｎ_0.9Ｏ第２クラッド層
２１２ 多層反射膜[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a semiconductor light emitting element such as a semiconductor laser, and more particularly to an oxide semiconductor light emitting element having a low oscillation threshold current and excellent reliability.
[0002]
[Prior art]
  Zinc oxide (ZnO) is a direct transition type semiconductor having a band gap energy of about 3.4 eV, exciton binding energy is as high as 60 meV, the raw material is inexpensive, harmless to the environment and the human body, and the film formation method is simple. There is a possibility that a light-emitting device having characteristics such as high efficiency and low power consumption and excellent environmental performance can be realized.
[0003]
  In the following, the ZnO-based semiconductor includes ZnO and mixed crystals represented by MgZnO or CdZnO based on the ZnO.
[0004]
  In the semiconductor laser element, the light emitting end face is 10^Five-10⁶W / cm²It is exposed to extremely high density light energy. For this reason, even if there is a minute defect or the like on the light emitting end face, the minute defect or the like propagates and propagates during the laser operation. In a conventional semiconductor laser device using a III-V group compound semiconductor such as AlGaAs or InGaAsP, the main cause of such defects is the progress of oxidation at the light emitting end face. That is, the elements constituting the III-V compound semiconductor include metals that are easily oxidized, such as Al and Ga, and these metals react with oxygen adsorbed on the light emitting end face based on a group having a high light energy density. Then, an oxide is formed by cutting the bond with the base semiconductor. When the minute defects generated in this manner are repeatedly propagated, the semiconductor crystal on the light emitting end face is remarkably broken and the element is deteriorated (for example, see Non-Patent Document 1).
[0005]
  In order to prevent element degradation due to the progress of oxidation, a protective film is usually formed on the light emitting end face of the semiconductor laser element. As the material of this protective film, it is considered that the light emitting end face is preferably not in contact with oxygen in consideration of the deterioration mechanism as described above, and sulfide is used (for example, see Patent Documents 1 to 4). ).
[0006]
  In addition, Group III nitride semiconductors, which are in practical use as semiconductor laser elements in the blue to ultraviolet region, are chemically extremely stable, so that even if the light emitting end face is exposed to a high energy density, it is difficult to cause damage, and a protective film It is possible to manufacture a highly reliable semiconductor laser device without using the above.
[0007]
[Non-Patent Document 1]
          Applied Physics Letters, 1974, Vol. 25, No. 12, p708
[Patent Document 1]
          JP-A-4-3698585
[Patent Document 2]
          JP-A-3-149898
[Patent Document 3]
          JP-A-4-091484
[Patent Document 4]
          JP-A-9-121076
[0008]
[Problems to be solved by the invention]
  By the way, in a ZnO-based semiconductor laser device composed of a ZnO-based semiconductor, since the ZnO-based semiconductor is an oxide semiconductor, deterioration due to the progress of oxidation does not occur unlike the conventional III-V group compound semiconductor laser device.
[0009]
  However, according to the study by the present inventors, there is a problem that a practical element lifetime cannot be secured unless a protective film is formed on the light emitting end face of the ZnO-based semiconductor laser element.
[0010]
  It has been found that even if a protective film similar to that of the conventional semiconductor laser element is formed on the light emitting end face of the ZnO-based semiconductor laser element, the growth of defects on the light emitting end face cannot be suppressed.
[0011]
  Further, the end face reflectance of the ZnO-based semiconductor laser element is approximately 20% with respect to blue to ultraviolet light, and is smaller than the end face reflectance of 30% of the conventional III-V group compound semiconductor laser element. Therefore, the ZnO-based semiconductor laser element has a larger reflection loss than the conventional III-V group compound semiconductor laser element. As a result, the ZnO-based semiconductor laser device has a problem that the oscillation threshold current increases.
[0012]
  SUMMARY OF THE INVENTION An object of the present invention is to provide an oxide semiconductor light emitting device with excellent reliability that can extend the device life and reduce the oscillation threshold current.
[0013]
[Means for Solving the Problems]
  According to the detailed study by the present inventors, the deterioration of the light emitting end face in the ZnO-based semiconductor laser element is mainly caused by reduction due to adsorption of moisture or the like, and in the conventional end face protection technology that plays a large role in preventing oxidation. Therefore, it is considered that reducing deterioration cannot be suppressed.
[0014]
  In consideration of the above causes, the present inventors have intensively studied the structure of an oxide semiconductor light emitting device excellent in reliability that can ensure a practical device lifetime and can reduce the oscillation threshold current. As a result, the inventors have found that the above object can be achieved by protecting the light emitting end face of the semiconductor laser element with a protective film made of metal oxide.
[0015]
  The oxide semiconductor light emitting device of the present invention is
  At least a first conductivity type cladding layer, an active layer, a second conductivity type cladding layer, and a second conductivity type contact layer are sequentially stacked on the substrate,
  The first conductivity type cladding layer, the active layer, the second conductivity type cladding layer and the second conductivity type contact layer are made of a ZnO-based semiconductor,
  A waveguide having the first conductivity type cladding layer, the active layer, and the second conductivity type cladding layer;
  An optical resonator having a light emitting end face and a light reflecting end face perpendicular to the extending direction of the waveguide;
With
  The light emitting end face and the light reflecting end face are made of a ZnO-based semiconductor,
  On at least one of the light emitting end surface and the light reflecting end surface, a plurality of metal oxides having different refractive indexes and a protective film composed of a plurality of layers are formed.,
  The protective film includes a MgZnO mixed crystal that is in contact with the light emitting end face or the light reflecting end face and has a band gap larger than the band gap of the active layer.It is characterized by that.
[0016]
  Here, the term “at least” means that a light guide layer, an etching stop layer, a planarization layer, a cap layer, and the like on both sides of the active layer may be provided.
[0017]
  In the present specification, the first conductivity type means p-type or n-type. The second conductivity type means n-type when the first conductivity type is p-type, and p-type when the first conductivity type is n-type.
[0018]
  According to the oxide semiconductor light emitting device having the above configuration, the metal oxide has good affinity with the ZnO-based semiconductor and excellent adhesion. Therefore, by forming the protective film including the plurality of metal oxide layers on at least one of the light emitting end face and the light reflecting end face, at least one of the light emitting end face and the light reflecting end face is protected from the reducing atmosphere. I can do it. That is, the protective effect from the reducing atmosphere is enhanced. As a result, the growth of defects is suppressed on at least one of the light emitting end face and the light reflecting end face, and the device life can be extended. That is, an oxide semiconductor light-emitting element with excellent reliability with respect to long-time driving can be manufactured.
[0019]
  Further, by forming the protective film including the plurality of metal oxide layers on at least one of the light emitting end face and the light reflecting end face, the end face reflectivity of the element is increased, and the reflection loss is reduced. The oscillation threshold current can be reduced.
  The MgZnO mixed crystals and BeZnO mixed crystals are wide gap ZnO-based semiconductors, have excellent affinity with ZnO, and have a higher refractive index than metal oxide dielectrics. The protective film includes the wide gap ZnO-based semiconductor, so that the end face reflectance can be finely controlled. Therefore, since the protective film includes a ZnO-based semiconductor having a band gap larger than that of the active layer, the end face reflectance can be finely controlled. As a result, an oxide semiconductor light-emitting element with excellent optical characteristics can be manufactured.
[0020]
  The oxide semiconductor light emitting device of one embodiment emits laser light from the light emitting end face.
[0021]
  In the oxide semiconductor light emitting device of one embodiment, the metal oxide included in the protective film is amorphous or single crystal.
[0022]
  According to the oxide semiconductor light emitting device of the above embodiment, the metal oxide is amorphous or single crystal, and thus does not include a crystal grain boundary. Thereby, the proliferation of defects on the light emitting end face or the light reflecting end face is suppressed. Therefore, the protective effect of the protective film against the light emitting end face or the light reflecting end face can be enhanced.
[0023]
  In one embodiment, the protective film is an amorphous film or a single crystal thin film.
[0024]
  According to the oxide semiconductor light emitting device of the above embodiment, the protective film is an amorphous film or a single crystal film, and thus does not include a crystal grain boundary. This reliably suppresses the growth of defects on the light emitting end face or the light reflecting end face. Therefore, the protective effect of the protective film against the light emitting end face or the light reflecting end face can be further enhanced.
[0025]
  In one embodiment, the protective film includes Mg (magnesium), Sc (scandium), Y (yttrium), Ti (titanium), Zr (zirconium), Hf (hafnium), and Ce (cerium). , V (vanadium), Nb (niobium), Ta (tantalum), Mo (molybdenum), W (tungsten), Re (rhenium), Al (aluminum), Ga (gallium), Si (silicon) and Ge (germanium) At least one of the oxides.
[0026]
  According to the oxide semiconductor light emitting device of the above embodiment, the protective film includes Mg, Sc, Y, Ti, Zr, Hf, Ce, V, Nb, Ta, Mo, W, Re, Al, Ga, Si, and Since it contains at least one of Ge oxides, it is easy to assume an amorphous or single crystal structure. Therefore, the crystal grain boundary of the protective film can be reduced.
[0027]
[0028]
[0029]
[0030]
[0031]
[0032]
[0033]
[0034]
  In the oxide semiconductor light emitting device of one embodiment, the layer thickness of each of the plurality of layers constituting the protective film is approximately λ / (4n) (where λ: oscillation wavelength, n: refraction of the protective film) Rate).
[0035]
  According to the oxide semiconductor light emitting device of the above embodiment, since the layer thickness per layer of the plurality of layers constituting the protective film is approximately λ / (4n), the number of protective films having high reflectivity is reduced. Can be formed with numbers.
[0036]
  The oxide semiconductor light emitting device of one embodiment isThe MgZnO mixed crystal isAmong the above metal oxides, the band gap energy is the largest.Yes.
[0037]
  According to the oxide semiconductor light emitting device of the above embodiment, the reflectance of the protective film is controlled by alternately laminating thin films having a large refractive index and thin films having a small refractive index. High band gap energy. Since the metal oxide having a large band gap energy is in contact with the ZnO-based semiconductor (light emitting end surface or light reflecting end surface), the band gap offset with the ZnO-based semiconductor is large, so that current leakage can be prevented. Low current and end face damage prevention are realized.
[0038]
  In one embodiment, the oxide semiconductor light emitting device includes the protective film formed on the light emitting end face and the light reflecting end face, the protective film formed on the light emitting end face, and the light reflecting end face. The reflectance is different from the above-described protective film.
[0039]
  According to the oxide semiconductor light emitting device of the above embodiment, since the protective film is formed on the light emitting end face and the light reflecting end face, the reliability can be further improved.
[0040]
  Further, one end surface of the protective film formed on the light emitting end surface and the protective film formed on the light reflecting end surface is a high reflection surface, and the other end surface is a low reflection surface. Thus, loss can be suppressed and light emission efficiency can be improved.
[0041]
  In the oxide semiconductor light emitting device of one embodiment, the reflectance of the protective film is in the range of 5% to 35% or 70% to 95%.
[0042]
  According to the oxide semiconductor light emitting device of the above embodiment, sufficient light output can be ensured by setting the reflectance of the protective film formed on the light emitting end face to 5% to 35%.
[0043]
  Further, the light emission efficiency can be improved by setting the reflectance of the protective film formed on the light reflection end face to 70% to 95%.
[0044]
DETAILED DESCRIPTION OF THE INVENTION
  Before describing an embodiment of the present invention, first, Reference Example 1 will be described in order to make the present invention easier to understand.
[0045]
  (Reference example1)
  BookReference example1, an example in which the present invention is applied to a ZnO-based semiconductor laser element will be described.
[0046]
  Figure 1 shows the bookReference example1 is a schematic perspective view of the ZnO-based semiconductor laser device 1 and FIG. 2 is a schematic side view of the semiconductor laser device.
[0047]
  As shown in FIGS. 1 and 2, the semiconductor laser element has a Ga doping concentration of 1 × 10 on an n-type ZnO single crystal substrate 101 having a zinc surface as a main surface.¹⁸cm^-3N-type ZnO buffer layer 102 having a thickness of 0.1 μm and a Ga doping concentration of 3 × 10¹⁸cm^-3N-type Mg with a thickness of 1 μm_0.1Zn_0.9O cladding layer 103, Ga doping concentration of 5 × 10¹⁷cm^-330 nm thick n-type ZnO light guide layer 104, non-doped quantum well active layer 105, and N doping concentration of 1 × 10¹⁸cm^-330 nm thick p-type ZnO light guide layer 106, N doping concentration is 5 × 10¹⁹cm^-3P-type Mg with a thickness of 1.2 μm_0.1Zn_0.9O cladding layer 107, N doping concentration of 1 × 10²⁰cm^-3A p-type ZnO contact layer 108 having a thickness of 0.5 μm is sequentially stacked.
[0048]
  BookReference example1, the n-type ZnO single crystal substrate 101 is an example of the substrate, and n-type Mg_0.1Zn_0.9The O-clad layer 103 is an example of a first conductivity type cladding layer, the quantum well active layer 105 is an example of an active layer, and a p-type Mg_0.1Zn_0.9The O cladding layer 107 corresponds to an example of a second conductivity type cladding layer, and the p-type ZnO contact layer 108 corresponds to an example of a second conductivity type contact layer.
[0049]
  The quantum well active layer 105 includes a ZnO barrier layer having a thickness of 5 nm and a Cd having a thickness of 6 nm._0.1Zn_0.9O well layers are alternately stacked. While there are two ZnO barrier layers, Cd_0.1Zn_0.9There are three O well layers.
[0050]
  The p-type ZnO contact layer 108 and the p-type Mg_0.1Zn_0.9The upper part of the O-cladding layer 107 is etched into a ridge stripe shape, and the side surface is n-type Mg_0.2Zn_0.8The O current blocking layer 109 is embedded. That is, the p-type ZnO contact layer 108 and the p-type Mg_0.1Zn_0.9On both sides of the top of the O-cladding layer 107, n-type Mg_0.2Zn_0.8An O current blocking layer 109 is formed. N-type Mg_0.2Zn_0.8The O current blocking layer 109 has Ga of 3 × 10¹⁸cm^-3Is doped at a concentration of
[0051]
  An n-type ohmic electrode 110 is formed under the n-type ZnO single crystal substrate 101, while a p-type ZnO contact layer 108 and an n-type Mg are formed._0.2Zn_0.8A p-type ohmic electrode 111 is formed on the O current blocking layer 109.
[0052]
  The semiconductor laser element includes n-type Mg._0.1Zn_0.9O-clad layer 103, quantum well active layer 105, and p-type Mg_0.1Zn_0.9A waveguide having an O-cladding layer 107 and an optical resonator having a light emitting end face 113 and a light reflecting end face 114 perpendicular to the extending direction of the waveguide are provided. The light emitting end face 113 and the light reflecting end face 114 are formed by cleavage. An oxide multilayer film 112A as an example of a protective film is formed on the light emitting end face 113, and an oxide multilayer film 112B as an example of a protective film is also formed on the light reflecting end face 114. Both of the oxide multilayer films 112A and 112B are a 60 nm thick MgO layer as an example of a metal oxide and a 70 nm thick SiO2 as an example of a metal oxide.₂The layers consist of alternating layers. In addition, the oxide multilayer films 112A and 112B are formed of the MgO layer and the SiO2 so that the reflectance with respect to light having a wavelength of 410 nm is 20%.₂The number of layers is adjusted.
[0053]
  BookReference exampleWhen a current was passed through one semiconductor laser element, blue oscillation light having a wavelength of 410 nm was obtained from the light emitting end face 113. In the semiconductor laser device, the oscillation threshold current was 40 mA, and the device lifetime (defined as the time when the continuous oscillation was performed at 60 ° C. and the optical output of 5 mW and the operating current was increased by 20% from the initial value) was 5000 hours. .
[0054]
  Table 1 below shows the oscillation threshold currents and device lifetimes of Comparative Examples 1 to 5 in which the front surface (light emitting end surface) and the rear surface (light emitting end surface) are not protected by various multilayer films.
[0055]
  In Comparative Examples 1 to 5, the number of multilayer films was adjusted so that the light reflectances of the front and rear surfaces were the same as when the front and rear surfaces were not protected (20%).
[0056]
  The element lifetime is a time when the operating current is increased by 20% from the initial value at 60 ° C. and an optical output of 5 mW (continuous oscillation).
[0057]
  Also bookReference example1 MgO / SiO₂In the multilayer film, the MgO layer is in contact with the end faces (front face and rear face) of the ZnO-based semiconductor laser element._ThreeN_Four/ MgO multilayer film is made of Si on the end face of ZnO-based semiconductor laser device._ThreeN_FourLayers are touching.
[0058]
[Table 1]

[0059]
  From the results of Table 1 above, when the end face protection is not performed (Comparative Example 5) or when only the sulfur treatment is performed (Comparative Example 4), the front face and the rear face are protected by the multilayer film containing MgO (thisReference example1 and Comparative Example 1) show that the oscillation threshold current is lower and the device life is improved.
[0060]
  Also bookReference exampleFrom the comparison between 1 and Comparative Example 3, it can be seen that the oxide multilayer film has a stronger protective effect when it is formed on both end faces than only one end face. That is, even if end face protection is performed with a multilayer film containing MgO on one of the front and rear surfaces, the device life can be extended as compared with the case where end face protection is not performed on the front and rear surfaces. In both cases, if the end face is protected with a multilayer film containing MgO, the device life can be further extended. Further, by performing end face protection on both the front and rear surfaces with a multilayer film containing MgO, an effect of reducing the threshold current can be obtained.
[0061]
  And booksReference exampleFrom the comparison between 1 and Comparative Example 1, it can be seen that the protective film has a higher effect of improving the characteristics when it is composed of a stack of metal oxides.
[0062]
  In addition, bookReference exampleFrom the results of 1 and Comparative Example 2, it can be seen that the effect of improving the characteristics is higher when the oxide layer is in contact with the end face of the ZnO-based semiconductor laser device. That is, the effect of improving the characteristics can be enhanced by bringing the metal oxide layer included in the multilayer film into contact with the light emitting end face or the light reflecting end face of the semiconductor laser element.
[0063]
  From the above results, the device life is increased by forming a multilayer film containing a plurality of metal oxides having different refractive indexes on at least one of the light emitting end face and the light reflecting end face of the ZnO-based semiconductor laser element. It turns out that reliability improves. This is because the metal oxide is the same oxide as the ZnO-based semiconductor and has good affinity and excellent adhesion. Particularly, a multilayer film composed of a plurality of metal oxide layers is formed on the light emitting end face and the light reflecting end face. This is considered to be because the effect of protecting the light emitting end face and the light reflecting end face from the reducing atmosphere is enhanced.
[0064]
  If the metal oxide crystal includes a grain boundary, it is likely to be destroyed when exposed to high light energy. Therefore, it is preferable to use a metal oxide that is amorphous or single crystal. More preferably, the multilayer film formed on the light emitting end face and the light reflecting end face is an amorphous or single crystal thin film.
[0065]
  As the metal constituting the oxide multilayer film, Mg, Sc, Y, Ti, Zr, Hf, Ce, V, Nb, Ta, Mo, W, Re, Al, Ga, Si, and Ge are preferable. Since many of the metal ions of these metals have no anisotropy in the electron orbit, the metal oxide is likely to be amorphous or single crystal.
[0066]
  BookReference example1, the MgO layer and SiO₂The layers are prepared so that the thickness of each layer is approximately λ / (4n) (λ: oscillation wavelength, n: refractive index of the oxide layer). Thereby, the oxide multilayer films 112A and 112B are preferable because the phases of reflected light from the respective boundaries (boundaries between the respective layers) with respect to the incident light are all aligned and a high reflectance is obtained.
[0067]
  Note that the light reflection at the oxide multilayer films 112A and 112B does not change the phase at the boundary from the oxide layer having a high refractive index to the oxide layer having a low refractive index. Changes by π.
[0068]
  (Execution formstate)
  This embodimentStateA ZnO-based semiconductor laser device has an Mg thickness of 55 nm._0.3Zn_0.7O layer and 40nm thick TiO₂Except that an oxide multilayer film composed of alternating layers with layers is used instead of the oxide multilayer films 112A and 112B.Reference example1 was produced.
[0069]
  This embodimentStateThe oxide multilayer film has Mg on the light emitting end face and the light reflecting end face._0.3Zn_0.7The O layer is formed in contact. In addition, the Mg_0.3Zn_0.7O layer and TiO₂The number of layers is adjusted so that the reflectance of the oxide multilayer film with respect to light having a wavelength of 410 nm is 20%.
[0070]
  This embodimentStateWhen a current was passed through the semiconductor laser element, blue oscillation light having a wavelength of 410 nm was obtained from the light emitting end face, and the oscillation threshold current and element lifetime wereReference exampleIt was the same as 1.
[0071]
  As Comparative Example 6, TiO is formed on the light emitting end face and the light reflecting end face.₂Except that the oxide multilayer film is formed so that the layers are in contact, this embodimentState andSimilarly, a semiconductor laser element was produced. The semiconductor laser device of Comparative Example 2 has an oscillation threshold current of the present embodiment.StateThe device life was increased by 20% and the device life was shortened by 30%.
[0072]
  In the semiconductor laser device of Comparative Example 6, TiO₂Mg_0.3Zn_0.7Since the band gap energy is smaller than that of O, it is considered that the characteristics are deteriorated by the leakage current from the ZnO semiconductor. Therefore, it is preferable that the metal oxide having the largest band gap energy among the metal oxides constituting the multilayer film is in contact with the ZnO semiconductor. That is, it is preferable that the metal oxide having the largest band gap energy among the plurality of metal oxides included in the oxide multilayer film is in contact with the light emitting end face and the light reflecting end face.
[0073]
  (Reference example 2)
  BookReference example 2This ZnO-based semiconductor laser device has a CaHfO thickness of 35 nm._ThreeExcept that an oxide multilayer film composed of alternating layers of CeO layers with a thickness of 50 nm is used instead of the oxide multilayer films 112A and 112B.Reference example1 was produced.
[0074]
  BookReference example 2When a current was passed through the semiconductor laser element, blue oscillation light having a wavelength of 410 nm was obtained from the light emitting end face, and the oscillation threshold current and element lifetime wereReference exampleIt was the same as 1.
[0075]
  In FIG. 3 (a), αβO_ThreeThe surface structure of a perovskite oxide having the following composition is shown. FIG. 3B shows the surface structure of ZnO.
[0076]
  As shown in FIGS. 3A and 3B, the (111) plane of the perovskite structure has a surface structure similar to the (0001) plane of a wurtzite crystal structure such as a ZnO-based semiconductor. For this reason, perovskite is excellent in affinity with a ZnO-based semiconductor, and crystal defects are extremely small when stacked on a ZnO interface.
[0077]
  ΑβO of such perovskite_ThreePreferably satisfies any one of the following conditions (a) to (c).
(A) The α element includes one or more selected from Li, Na, and K, and the β element includes Ta or Nb.
(B) The element of α includes one or more selected from Cd, Ca, Sr, Ba and Bi, and the element of β includes one or more selected from Ti, Zr, Hf and Sn. Including.
(C) The element of α includes one or more selected from Bi, rare earth, and alkaline earth, and the element of β includes one or more selected from In, Al, Ga, and Sc.
[0078]
  In particular, the above αβO_ThreeIs KNbO_Three, KTaO_Three, BaTiO_Three, CaSnO_Three, CaZrO_Three, CaHfO_Three, CdSnO_Three, SrHfO_Three, SrSnO_Three, SrTiO_ThreeAnd YScO_ThreeIf it is any one of these, it will become easy to match | combine a hexagonal lattice shape with a ZnO (0001) surface, and a high quality multilayer reflective film with very few interface defects can be formed.
[0079]
  (Reference example 3)
  BookReference example 3In the ZnO-based semiconductor laser device, the MgO layer and SiO₂By adjusting the number of layers with the layer, the reflectance of the oxide multilayer film on the light emitting end face was set to 10%, and the reflectance of the oxide multilayer film on the light reflecting end face was set to 80%.Reference exampleIn the same manner as in Example 1, an oxide semiconductor light emitting device of the present invention was produced.
[0080]
  BookReference example 3When a current was passed through the semiconductor laser element, blue oscillation light having a wavelength of 410 nm was obtained from the light emitting end face. The semiconductor laser element has an oscillation threshold current of the aboveReference exampleCompared to 1, the device life is reduced by 20%.Reference example20% longer than 1.
[0081]
  BookReference example 3As described above, the light emission efficiency can be improved by increasing the reflectivity of the oxide multilayer film on the light reflection end face while reducing the reflectivity of the oxide multilayer film on the light output end face. .
[0082]
  The oxide multilayer film as an example of the protective film of the present invention not only protects the ZnO-based semiconductor laser element from the reducing atmosphere, but also can control the reflectance by the number of stacked layers, thereby reducing the reflection loss and the oscillation threshold. A semiconductor laser element having excellent reliability can be manufactured by reducing the current.
[0083]
  If the reflectance of the oxide multilayer film on the light emitting end face is 5% to 35%, sufficient light output can be secured. Moreover, if the reflectance of the oxide multilayer film on the light reflection end face is 70% or more, sufficient reflectance can be secured. However, when the light output from the light reflection end face is detected by the light receiving element in order to monitor the light output of the semiconductor laser element, the reflectivity of the oxide multilayer film on the light reflection end face is preferably 95% or less.
[0084]
  (Reference example 4)
  BookReference example 4Now, an example in which the present invention is applied to a surface-emitting ZnO-based semiconductor laser element will be described.
[0085]
  Figure 4 shows the bookReference example 41 is a schematic perspective view of the surface emitting semiconductor laser element. This semiconductor laser element has a structure for extracting oscillation light from the substrate side, and the structure shown in FIG. 4 is upside down from the stacking order. That is, in FIG. 4, in the plurality of growth layers under the n-type ZnO single crystal substrate 201, the upper growth layer in the drawing is stacked before the lower growth layer in the drawing.
[0086]
  In the following description, it is assumed that the plurality of growth layers are formed on the substrate. That is, the upper and lower sides in the following description are opposite to the upper and lower sides in FIG.
[0087]
  The surface-emitting type semiconductor laser device has a 20 nm-thick Mg layer on an n-type ZnO single crystal substrate 201 whose main surface is a zinc surface._0.15Zn_0.85O first etching stop layer 202, Ga doping concentration is 1 × 10¹⁸cm^-3And an n-type ZnO buffer layer 203 having a thickness of 0.1 μm and a Ga doping concentration of 1 × 10¹⁸cm^-3N-type Mg with a thickness of 1.0 μm_0.1Zn_0.9O-clad layer 204, non-doped quantum well active layer 205, N doping concentration is 5 × 10¹⁸cm^-3P-type Mg with a thickness of 0.1 μm_0.1Zn_0.9O first cladding layer 206, Mg with a thickness of 20 nm_0.15Zn_0.85O second etching stop layer 207, N doping concentration is 5 × 10¹⁹cm^-3P-type Mg with a thickness of 1.1 μm_0.1Zn_0.9O second cladding layer 208, N doping concentration of 1 × 10²⁰cm^-3The p-type ZnO contact layer 209 having a thickness of 0.5 μm is laminated in this order.
[0088]
  BookReference example 4Then, n-type ZnO single crystal substrate 201 is an example of the substrate, n-type Mg_0.1Zn_0.9The O clad layer 204 is an example of the first conductivity type clad layer._0.15Zn_0.85The surface of the O first etching stop layer 202 on the n-type ZnO single crystal substrate 201 side is an example of the light emitting end face, the quantum well active layer 205 is an example of the active layer, and the p-type ZnO contact layer 209 is the second conductivity type contact. Each corresponds to an example of a layer. In addition, the p-type Mg_0.1Zn_0.9O first cladding layer 206 and p-type Mg_0.1Zn_0.9The O second cladding layer 208 constitutes an example of a second conductivity type cladding layer.
[0089]
  The quantum well active layer 205 includes two ZnO barrier layers having a thickness of 5 nm and Cd having a thickness of 6 nm._0.05Zn_0.95Three O well layers are alternately stacked. While there are two ZnO barrier layers, Cd_0.05Zn_0.95There are three O well layers.
[0090]
  P-type ZnO contact layer 209 and p-type Mg_0.1Zn_0.9The O second cladding layer 208 is etched into a cylindrical shape, and the side surface is n-type Mg_0.3Zn_0.7The O current blocking layer 210 is embedded. That is, the p-type ZnO contact layer 209 and the p-type Mg_0.1Zn_0.9The O second cladding layer 208 is formed of n-type Mg in a direction substantially parallel to the surface of the n-type ZnO single crystal substrate 201._0.3Zn_0.7O current blocking layer 210 is surrounded. This n-type Mg_0.3Zn_0.7The O current blocking layer 210 has Ga of 1 × 10¹⁸cm^-3Is doped at a concentration of
[0091]
  An n-type ohmic electrode 211 is formed under the n-type ZnO substrate 201. In the n-type ohmic electrode 211 and the n-type ZnO substrate 201, the p-type ZnO contact layer 209 and the p-type Mg_0.1Zn_0.9A portion corresponding to the portion immediately below the O second cladding layer 218 is removed by etching to form an opening. Mg exposed by this etching_0.15Zn_0.85Under the O first etching stop layer 207, a multilayer reflective film 212 as an example of a protective film is formed. This multilayer reflective film 212 is made of CaZrO as an example of a metal oxide._ThreeAnd Al as an example of a metal oxide₂O_ThreeIt is comprised by alternating lamination. The multilayer reflective film 212 has a CaZrO of 20% so that the reflectance with respect to light having a wavelength of 400 nm is 20%._ThreeAnd Al₂O_ThreeThe number of layers has been adjusted.
[0092]
  On the p-type ZnO contact layer 209, a p-type ohmic electrode 213, an Ag high reflection electrode 214, and an Au pad electrode 215 are sequentially formed. The Ag high reflection film 214 has a reflectance of 95% for light emission with a wavelength of 200 nm.
[0093]
  BookReference example 4When a current was passed through the semiconductor laser element, blue oscillation light having a wavelength of 400 nm was obtained from the opening.
[0094]
  As Comparative Example 7, the present example except that the multilayer reflective film 212 is not formed isReference example 4A surface emitting semiconductor laser device was fabricated in the same manner as described above. The surface emitting semiconductor laser device of Comparative Example 7 isReference example 4The oscillation threshold current is increased by 10% compared to the above, and the device life is reduced to 1/10.
[0095]
  As Comparative Example 8, the multilayer reflective film 212 is made of Si._ThreeN_FourOther than that composed of alternating layers of AlN and AlNReference example 4A surface emitting semiconductor laser device was fabricated in the same manner as described above. In the surface emitting semiconductor laser device of Comparative Example 8, the oscillation threshold current isReference example 4The device life is about the same asReference example 420% shorter.
[0096]
  BookReference example 4As a result, the present invention is effective even for a surface-emitting type ZnO-based semiconductor laser element. By forming a multilayer film containing a metal oxide on the light emitting end face, the lifetime of the element is prolonged and the reliability is increased. It can be seen that the property is improved.
[0097]
  Embodiment aboveAnd Reference Example 1The preferred conditions described in ~ 3 areReference example 4It goes without saying that it may be used for the above.
[0098]
  Also bookReference example 4Then, the Ag high reflection electrode 214 corresponds to an example of a light reflection end face.
[0099]
  Embodiment aboveandReference Example 14This semiconductor laser device has a structure in which at least an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer are sequentially stacked on a substrate. The clad layer, the active layer, the n-type clad layer, and the n-type contact layer may be sequentially laminated.
[0100]
【The invention's effect】
  As is clear from the above, the oxide semiconductor light emitting device of the present invention includes a plurality of metal oxides having different refractive indexes on at least one of the light emitting end face and the light reflecting end face of the optical resonator. Since the protective film composed of a plurality of layers is formed, the affinity between the protective film and the ZnO-based semiconductor is good, and the protective film has a high protective effect from the reducing atmosphere. Therefore, the device life can be extended and the oscillation threshold current can be reduced. That is, an oxide semiconductor light-emitting element with excellent reliability with respect to long-time driving can be manufactured.
[Brief description of the drawings]
FIG. 1 illustrates the present invention.Reference example1 is a schematic perspective view of one ZnO-based semiconductor laser element.
FIG. 2 shows the aboveReference example1 is a schematic side view of a ZnO-based semiconductor laser device No. 1;
FIG. 3A is a diagram showing a surface structure of a perovskite oxide, and FIG. 3B is a diagram showing a surface structure of ZnO.
FIG. 4 shows the present invention.Reference example 4It is a model perspective view of this surface emitting semiconductor laser element.
[Explanation of symbols]
101,201 n-type ZnO single crystal substrate
103,204 n-type Mg_0.1Zn_0.9O-clad layer
105,205 Quantum well active layer
107 p-type Mg_0.1Zn_0.9O-clad layer 107
108,209 p-type ZnO contact layer
113 Light exit end face
114 Light reflection end face
206 p-type Mg_0.1Zn_0.9O first cladding layer
208 p-type Mg_0.1Zn_0.9O second cladding layer
212 Multi-layer reflective film

Claims (7)

At least a first conductivity type cladding layer, an active layer, a second conductivity type cladding layer, and a second conductivity type contact layer are sequentially stacked on the substrate,
The first conductivity type cladding layer, the active layer, the second conductivity type cladding layer and the second conductivity type contact layer are made of a ZnO-based semiconductor,
A waveguide having the first conductivity type cladding layer, the active layer, and the second conductivity type cladding layer;
An optical resonator having a light emitting end face and a light reflecting end face perpendicular to the extending direction of the waveguide,
The light emitting end face and the light reflecting end face are made of a ZnO-based semiconductor,
On the at least one of the light emitting end surface and the light reflecting end surface, a plurality of metal oxides having different refractive indexes are formed, and a protective film composed of a plurality of layers is formed .
The oxide semiconductor light emitting element, wherein the protective film includes a MgZnO mixed crystal having a band gap larger than a band gap of the active layer while being in contact with the light emitting end face or the light reflecting end face . The oxide semiconductor light emitting device according to claim 1,
The oxide semiconductor light emitting element, wherein the protective film is an amorphous film or a single crystal thin film. The oxide semiconductor light emitting device according to claim 1,
The protective film contains at least one of oxides of Mg, Sc, Y, Ti, Zr, Hf, Ce, V, Nb, Ta, Mo, W, Re, Al, Ga, Si, and Ge. An oxide semiconductor light emitting device characterized by the above. The oxide semiconductor light emitting device according to claim 1,
The thickness of each of the plurality of layers constituting the protective film is approximately λ / (4n) (where λ is the oscillation wavelength and n is the refractive index of the protective film). Semiconductor light emitting device. The oxide semiconductor light emitting device according to claim 1,
The MgZnO mixed crystal, among the plurality of metal oxide, the oxide semiconductor light-emitting device bandgap energy and wherein when most us go large. The oxide semiconductor light emitting device according to claim 1,
The protective film is formed on the light emitting end face and the light reflecting end face,
The oxide semiconductor light-emitting element, wherein the protective film formed on the light emitting end face and the protective film formed on the light reflecting end face have different reflectances. The oxide semiconductor light emitting device according to claim 1,
The oxide semiconductor light-emitting element, wherein the protective film has a reflectance of 5% to 35% or 70% to 95%.

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