JP2004031925A - N-type semiconductor distributed bragg reflector, plane emission semiconductor laser device, plane emission laser array, plane emission laser module optical interconnection system, and optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an n-type semiconductor distributed bragg reflector that can reduce an electrostatic capacitance. <P>SOLUTION: The n-type semiconductor distributed Bragg reflector in which two kinds of semiconductor layer having a different refractive index are stuck and doped in an n-type, is provided with an intermediate layer (semiconductor layer) having a refractive index between the two kinds of semiconductor layers, between the two semiconductor layers having different refractive indexes (inhibited band width). <P>COPYRIGHT: (C)2004,JPO

Description

【００４９】
【数１】
閾値厚さ＝（５０λ−１５）［ｎｍ］
【００５０】
ここで、反射波長とは、分布ブラッグ反射器の反射帯域において、最も反射率が高くなる波長のことである。また、中間層を設けない構造においては、ブラッグ反射器を構成する屈折率がｎで表される層の厚さは、反射波長λに対しλ／４ｎと表される。
【００５１】
一方、上述の様に、駆動条件による電流−電圧特性の違い、及び非線形性、及びヘテロ界面におけるキャリアの蓄積、空乏化を改善する効果は、中間層の厚さが厚い場合において顕著であり、厚い中間層を設けることが望ましい。しかし、厚すぎる場合には上述の様な問題があるので、中間層の厚さには最適な範囲がある。
【００５２】
以上の結果から、電気特性（電流−電圧特性）と光学特性（反射率）との両方を考慮した場合に、最適な中間層の厚さの範囲を、分布ブラッグ反射器の反射波長λ［μｍ］に応じて、２０＜ｔ≦（５０λ−１５）［ｎｍ］と表すことができる。ここで、中間層厚さｔの範囲を定める不等式は、λ＞０．７μｍの範囲で成立し、この波長より長波の反射波長を有するｎ型分布ブラッグ反射器において適応することができる。例えば、ＡｌＧａＡｓ系材料を活性層材料に用いた素子は、典型的には０．７８μｍ〜０．８５μｍ帯においてレーザ発振を得ることができる。また、ＧａＩｎＡｓ系材料を用いた場合には、０．９８μｍ帯〜１．２μｍ帯においてレーザ発振を得ることができる。更に、ＧａＩｎＮＡｓＳｂＰ系材料を用いることにより、１．２μｍ帯よりも長波においてレーザ発振を得ることができる。
【００５３】
従って、この第４の実施形態の定める範囲の厚さの中間層を有したｎ型分布ブラッグ反射器は、これらを材料とした、波長が０．７μｍよりも長波の光を対象としたレーザや、光変調器等の光デバイスなどに用いることができる。
【００５４】
第５の実施形態
本発明の第５の実施形態は、第１〜第４のいずれかの実施形態のｎ型半導体分布ブラッグ反射器を用いた面発光半導体レーザ素子である。
【００５５】
この第５の実施形態の面発光半導体レーザ素子では、第１〜第４のいずれかの実施形態のｎ型半導体分布ブラッグ反射器が用いられることで、面発光半導体レーザ素子の静電容量が低減され、高速変調が可能となる。
【００５６】
すなわち、第５の実施形態の面発光半導体レーザ素子では、第１〜第４のいずれかの実施形態のｎ型半導体分布ブラッグ反射器を用いていることで、ｎ型半導体分布ブラッグ反射器の界面に形成されるスパイク，ノッチ等のポテンシャル分布が平滑化されている。従って、これによるキャリアの空乏，蓄積の影響が、従来の面発光半導体レーザ素子に比べて飛躍的に低減され、電気抵抗は勿論、ヘテロ界面における静電容量も低減されている。
【００５７】
従って、第５の実施形態の面発光半導体レーザ素子は、従来の面発光半導体レーザ素子に比べて高速変調に適した構造であり、ｎ型半導体分布ブラッグ反射器の静電容量が低減したことによって、１０Ｇｂｐｓを超える高速変調を容易に行うことができる。
【００５８】
第６の実施形態
本発明の第６の実施形態では、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器がメサ形状に加工されていることを特徴としている。
【００５９】
この第６の実施形態では、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器がメサ形状に加工されていることで、ｎ型半導体分布ブラッグ反射器を通して素子部（共振領域）に注入される電流の通路が限定され、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積が減少し、これによって、静電容量を低減することができ、高速変調が可能となる。
【００６０】
すなわち、第６の実施形態では、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器がメサ形状に加工されている（より具体的には、後述の図４の例のように、ｎ型半導体分布ブラッグ反射器の素子部（共振領域）以外の領域を基板表面までエッチングにより除去している）。前述のように、電子親和力の異なる２種の半導体層からなるヘテロ界面では、スパイクやノッチ等のポテンシャル分布が形成され、キャリアが空乏化することによる静電容量が発生している。また、従来、面発光レーザ素子では、閾値電流を低減する為に、ＡｌＡｓ等のＡｌを含む半導体層を酸化して形成される酸化狭窄構造が設けられている。正孔は、電子に比べ拡散長が短く高い狭窄効率が得られるので、前記の狭窄構造は、ｐ型半導体分布ブラッグ反射器側に設けられている。ｎ型半導体分布ブラッグ反射器側は、特に狭窄構造は設けられておらず、基板裏面全面に形成された電極から多数キャリアである電子の注入が行われる構造となっている。従って、従来の面発光半導体レーザ素子では、電子は正孔の通路であるメサ径に比べて広い電流通路を有し、ｎ型半導体分布ブラッグ反射器中の電子電流が通過する面積は、ｐ型半導体分布ブラッグ反射器よりも広い。静電容量は、面積に比例して増加するので、ｎ型半導体分布ブラッグ反射器による静電容量は、この電流の広がりに対応して増加し、素子容量を増加させている原因となっている。
【００６１】
この第６の実施形態では、具体的には、ｎ型半導体分布ブラッグ反射器の素子部（共振領域）以外の領域をエッチング除去することによって、エッチング除去によって残された領域に電子の電流通路を限定し、これによって、ｎ型半導体分布ブラッグ反射器による静電容量を低減することを可能としている。よって、この第６の実施形態の面発光半導体レーザ素子は、従来の面発光半導体レーザ素子に比べて高速変調に適した構造であり、この第６の実施形態の面発光半導体レーザ素子では、ｎ型半導体分布ブラッグ反射器の静電容量が低減されたことによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【００６２】
換言すれば、この第６の実施形態の面発光半導体レーザ素子では、ｎ型半導体分布ブラッグ反射器における電流通路を素子部（共振領域）のメサ径と同程度に狭窄することにより、静電容量として寄与するｎ型半導体分布ブラッグ反射器の面積を低減し、素子の静電容量の低減を図ることができ、高速変調が可能となる。
【００６３】
第７の実施形態
本発明の第７の実施形態では、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器の共振領域以外の領域が高抵抗化されていることを特徴としている。
【００６４】
この第７の実施形態では、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器の共振領域以外の領域が高抵抗化されていることで、ｎ型半導体分布ブラッグ反射器を通して素子部（共振領域）に注入される電流の通路が限定され、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積が減少し、これによって、静電容量を低減することができ、高速変調が可能となる。
【００６５】
すなわち、第７の実施形態では、ｎ型半導体分布ブラッグ反射器の素子部（共振領域）以外の領域を高抵抗化しており、第６の実施形態の説明と同様に、基板側から注入される電子の電流通路がｎ型半導体分布ブラッグ反射器のメサ領域の一部に限定されることによって、静電容量として寄与するｎ型半導体分布ブラッグ反射器の面積を低減し、これによって、面発光半導体レーザ素子の静電容量を従来の面発光半導体レーザ素子に比べ小さくすることができ、高速変調に適した構造を得ることができる。
【００６６】
換言すれば、この第７の実施形態の面発光半導体レーザ素子も、第６の実施形態と同様に、ｎ型半導体分布ブラッグ反射器における電流通路を素子部（共振領域）のメサ径と同程度に狭窄することにより、静電容量として寄与するｎ型半導体分布ブラッグ反射器の面積を低減し、素子の静電容量の低減を図ることができ、高速変調が可能となる。
【００６７】
なお、ｎ型半導体分布ブラッグ反射器を高抵抗化する方法としては、例えば後述の実施例５のように水素イオン注入等の方法を用いることができる。特に水素イオン注入を用いると、活性領域とエッチング表面の距離が近いことから、放熱に優れ、埋め込みが容易であり、物理強度が優れている等の利点がある。特に、放熱に優れていることによって、高出力を得ることが可能となる。実際、この第７の実施形態の面発光半導体レーザ素子では、ｎ型半導体分布ブラッグ反射器の静電容量を低減することによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【００６８】
第８の実施形態
本発明の第８の実施形態では、第６または第７の実施形態の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層（半導体層）が設けられていることを特徴としている。
【００６９】
この第８の実施形態では、第６または第７の実施形態の面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層（半導体層）が設けられていることで、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を飛躍的に低減することができ、より一層の高速変調が可能となる。
【００７０】
すなわち、第８の実施形態では、第６または第７の実施形態の面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器を構成する２種の半導体層のヘテロ界面に、２種の半導体層の間の屈折率（禁則帯幅）を有する中間層（半導体層）を設けている。第１〜第５のいずれかの実施形態において説明したように、上記中間層（半導体層）を２種の半導体層のヘテロ界面に設けることによって、ヘテロ界面におけるポテンシャルが平滑化され、キャリアの空乏，蓄積が低減し、空乏化によって生じる静電容量を飛躍的に低減することができる。更に、第６または第７の実施形態のように、ｎ型半導体分布ブラッグ反射器の電子の通路をメサ領域内に限定することによって、容量として実効的に寄与する半導体分布ブラッグ反射器の面積を低減することができる。従って、第８の実施形態のように、これらを合わせ用いることにより、より一層効果的に面発光半導体レーザ素子の静電容量を低減することができ、非常に高速変調に適した構造を得ることができる。実際、第８の実施形態の面発光半導体レーザ素子は、以上のようにｎ型半導体分布ブラッグ反射器の静電容量が低減したことによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【００７１】
第９の実施形態
本発明の第９の実施形態は、第６または第７の実施形態の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さが２０［ｎｍ］よりも厚い構成としている。
【００７２】
第９の実施形態の構成とすることで、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。
【００７３】
第１０の実施形態
本発明の第１０の実施形態は、第６または第７の実施形態の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さが３０［ｎｍ］以上の範囲である構成としている。
【００７４】
第１０の実施形態の構成とすることで、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。
【００７５】
第１１の実施形態
本発明の第１１の実施形態は、第６または第７の実施形態の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さｔ［ｎｍ］が、分布ブラッグ反射器の反射波長λ［μｍ］に対して、２０＜ｔ≦（５０λ−１５）［ｎｍ］の範囲である構成としている。
【００７６】
第１１の実施形態の構成とすることで、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。
【００７７】
第１２の実施形態
本発明の第１２の実施形態では、第５乃至第１１のいずれかの実施形態の面発光半導体レーザ素子において、活性層は、ＩＩＩ族材料とＶ族材料とにより構成されており、活性層のＩＩＩ族材料が、Ｇａ，Ｉｎのいずれか、または、全てであり、活性層のＶ族材料が、Ａｓ，Ｎ，Ｓｂ，Ｐのいずれか、または、全てであることを特徴としている。
【００７８】
この第１２の実施形態では、第５乃至第１１のいずれかの実施形態の面発光半導体レーザ素子において、活性層は、ＩＩＩ族材料とＶ族材料とにより構成されており、活性層のＩＩＩ族材料が、Ｇａ，Ｉｎのいずれか、または、全てであり、活性層のＶ族材料が、Ａｓ，Ｎ，Ｓｂ，Ｐのいずれか、または、全てであることで、ＧａＡｓ基板上に、光ファイバ通信で重要な１．３μｍ帯，１．５μｍ帯を含む１．１μｍよりも長波で発振する面発光半導体レーザ素子を得ることができる。また、ＧａＡｓを半導体基板として用いることができるので、ＡｌＧａＡｓ／ＧａＡｓによる高品質な半導体分布ブラッグ反射器を共振器ミラーに用いることができる。よって、閾値が低く、特性の優れた長波長帯の面発光半導体レーザ素子を提供することができる。
【００７９】
すなわち、第１２の実施形態では、活性層のＩＩＩ族材料が、Ｇａ，Ｉｎのいずれか、または、全てであり、活性層のＶ族材料が、Ａｓ，Ｎ，Ｓｂ，Ｐのいずれか、または、全てであり、これらの材料から構成される活性層は、ＧａＡｓ基板上に結晶成長が可能であり、反射率，熱伝導性，プロセス制御（結晶成長や、Ａｌ（Ｇａ）Ａｓ混晶等の選択酸化）の点において優れた特性を持つＡｌＧａＡｓ系材料によるＤＢＲを用いた面発光半導体レーザ素子を得ることができる。また、これらの材料を活性層に用いることで、０．８５μｍ帯，０．９８μｍ帯、更に光ファイバ通信で重要な１．３μｍ帯，１．５μｍ帯を含む１．１μｍよりも長波の発振を得ることができる。
【００８０】
これにより、例えば、波長１．３μｍ帯のレーザ素子と石英シングルモードレーザと組み合わせることによって、高速光通信が可能になる。また、１．５μｍ帯の素子によるＤＷＤＭを用いれば、大容量通信を行うことが可能である。
【００８１】
この際、特に、上述した材料（活性層材料）の中でも、ＧａＩｎＮ（Ｓｂ）Ａｓ混晶材料は、１．１μｍ以上の発振を得ることができる上に、キャリア閉じ込め層となるＧａＡｓ層に対して、ＧａＩｎＮ（Ｓｂ）Ａｓ層の伝導帯のバンド不連続量が大きく、電子のオーバーフローが低減できるので、高温まで安定な発振を得ることができる。これらに加えて、本発明の面発光半導体レーザ素子では、ｎ型半導体分布ブラッグ反射器の静電容量が低減されているので、従来の素子に比べて高速変調を容易に行なうことができる。従って、本発明によれば、光通信，光伝送用として好適な面発光半導体レーザ素子を提供することができる。
【００８２】
第１３の実施形態
本発明の第１３の実施形態は、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子によって構成された面発光レーザアレイである。
【００８３】
この第１３の実施形態の面発光レーザアレイは、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子によって構成されているので、素子の静電容量が従来よりも小さく、高速変調が可能となる。
【００８４】
すなわち、この第１３の実施形態の面発光レーザアレイを構成している面発光半導体レーザ素子は、ｎ型半導体分布ブラッグ反射器による静電容量が低減されていることによって、高速変調が可能であり、これらの面発光半導体レーザ素子によって構成されている面発光レーザアレイもまた、同様に高速変調が可能である。また、面発光レーザアレイを形成することによって、並列光伝送が容易となり、更に高速，大容量の光伝送，光通信を行うことが可能となる。このように、第１３の実施形態では、高速，大容量の光伝送，光通信が可能な面発光レーザアレイを提供することができる。
【００８５】
第１４の実施形態
本発明の第１４の実施形態は、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイによって構成された面発光レーザモジュールである。
【００８６】
この第１４の実施形態の面発光レーザモジュールは、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイによって構成されているので、高速，大容量の光伝送，光通信が可能となる。
【００８７】
すなわち、この第１４の実施形態の面発光レーザモジュールには、ｎ型半導体分布ブラッグ反射器の静電容量が低減され、従来よりも高速変調が可能な面発光半導体レーザ素子または面発光レーザアレイが用いられているので、高速，大容量の光伝送，光通信が可能となる。具体的に、後述の実施例７のように、ＧａＩｎＮＡｓ混晶半導体を活性層材料とした１．３μｍ帯面発光半導体レーザ素子と石英シングルモードファイバとを組み合わせた面発光レーザモジュールは、１．３μｍ帯が石英の零分散帯に当たるため、高速変調に非常に適した構成であり、この面発光レーザモジュールを用いることによって、高速，大容量の光通信、光伝送を行うことができる。このように、第１４の実施形態では、高速，大容量の光伝送，光通信が可能な面発光レーザモジュールを提供することができる。
【００８８】
第１５の実施形態
本発明の第１５の実施形態は、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイ、または、第１４の実施形態の面発光レーザモジュールによって構成された光インターコネクションシステムである。
【００８９】
この第１５の実施形態の光インターコネクションシステムは、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイ、または、第１４の実施形態の面発光レーザモジュールによって構成されているので、高速，大容量の光伝送が可能となる。
【００９０】
すなわち、この第１５の実施形態の光インターコネクションシステムには、ｎ型半導体分布ブラッグ反射器の静電容量が低減され、従来に比べて高速変調が可能な面発光半導体レーザ素子または面発光レーザアレイまたは面発光レーザモジュールが用いられているので、高速，大容量の光伝送，光通信が可能となる。具体的に、後述の実施例７のように、ＧａＩｎＮＡｓ混晶半導体を活性層材料とした１．３μｍ帯面発光レーザと石英シングルモードファイバとを組み合わせた面発光レーザモジュールによって構成された光インターコネクションシステムでは、１．３μｍ帯が石英の零分散帯に当たるため、高速変調に非常に適した構成であり、高速，大容量の光通信，光伝送を行うことができる。また、ＧａＩｎＮＡｓ混晶半導体を活性層とした面発光半導体レーザ素子は、素子の動作環境温度等の変化に対しても、高温まで、安定に発振を得ることが可能であるので、非常に信頼性の高い光インターコネクションシステムを得ることができる。このように、第１５の実施形態では、高速，大容量の光通信が可能であり、更に信頼性の高い光インターコネクションシステムを提供することができる。
【００９１】
第１６の実施形態
本発明の第１６の実施形態は、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイ、または、第１４の実施形態の面発光レーザモジュールによって構成された光通信システムである。
【００９２】
この第１６の実施形態の光通信システムは、第５乃至第１２のいずれかの実施形態の面発光半導体レーザ素子、または、第１３の実施形態の面発光レーザアレイ、または、第１４の実施形態の面発光レーザモジュールによって構成されているので、高速，大容量光通信が可能となる。
【００９３】
すなわち、第１６の実施形態の光通信システムには、ｎ型半導体分布ブラッグ反射器の静電容量が低減され、従来に比べて高速変調が可能な面発光半導体レーザ素子または面発光レーザアレイまたは面発光レーザモジュールが用いられているので、高速，大容量の光伝送，光通信が可能となる。具体的に、後述の実施例７のように、ＧａＩｎＮＡｓ混晶半導体を活性層材料とした１．３μｍ帯面発光レーザと石英シングルモードファイバとを組み合わせた面発光レーザモジュールによって構成された光通信システムでは、１．３μｍ帯が石英の零分散帯に当たるため、高速変調に非常に適した構成であり、高速，大容量の光伝送を行うことができる。また、ＧａＩｎＮＡｓ混晶半導体を活性層とした面発光半導体レーザ素子は、素子の動作環境温度等の変化に対しても、高温まで、安定に発振を得ることが可能であるので、非常に信頼性の高い光通信システムを得ることができる。このように、第１６の実施形態では、高速，大容量の光伝送が可能であり、更に信頼性の高い光通信システムを提供することができる。
【００９４】
【実施例】
次に、本発明の実施例を説明する。
【００９５】
（実施例１）
図１は、実施例１として第１の実施形態のｎ型半導体分布ブラッグ反射器の一例を説明するための図である。図１のｎ型半導体分布ブラッグ反射器は、０．９８μｍを設計反射波長とした半導体分布ブラッグ反射器であり、ｎ−ＡｌＡｓ層と、ｎ−ＧａＡｓ層と、ｎ−ＡｌＡｓ層とｎ−ＧａＡｓ層との間に図２のようにＡｌ組成を一方の値から他方の値に線形に変化させた厚さ３０ｎｍのｎ−ＡｌＧａＡｓ線形組成傾斜層（中間層）とが、周期的に積層されることによって構成されている。
【００９６】
ここで、図１のｎ型半導体分布ブラッグ反射器のｎ−ＡｌＡｓ層の厚さは５１．６ｎｍであり、ｎ−ＧａＡｓ層の厚さは４０．９ｎｍである。波長０．９８μｍの光に対して、各半導体層中における光の位相変化がπ／２となる厚さ、つまり半導体分布ブラッグ反射器における多重反射の位相条件を満たす厚さは、それぞれ８２．９ｎｍ、６９．５ｎｍであるが、厚さ３０ｎｍの線形組成傾斜層における位相変化を考慮し、ｎ−ＡｌＡｓ層と、ｎ−ＧａＡｓ層との厚さを上記の厚さとしている。
【００９７】
図１のｎ型半導体分布ブラッグ反射器は、トリメチルアルミニウム（ＴＭＡ），トリメチルガリウム（ＴＭＧ），アルシン（ＡｓＨ_３）ガスを原料として、ＭＯＣＶＤ法により結晶成長させることができる。また、ｎ型のドーパントにはセレン化水素（Ｈ_２Ｓｅ）を用いることができる。ＭＯＶＣＤ法では、原料の供給量を変化させることでＡｌＧａＡｓの組成を制御することができるので、容易に組成傾斜層を成長させることができる。
【００９８】
図１のｎ型半導体分布ブラッグ反射器では、各へテロ界面に組成傾斜層（中間層）を設けたことによって、電気抵抗は勿論、ヘテロ界面による静電容量を従来に比べて低減することができた。
【００９９】
（実施例２）
図１８は、実施例２として第３の実施形態のｎ型半導体分布ブラッグ反射器の一例を説明するための図である。図１のｎ型半導体分布ブラッグ反射器は、１．３μｍを設計反射波長とした半導体分布ブラッグ反射器であり、ｎ−Ａｌ_０．９Ｇａ_０．１Ａｓ層と、ｎ−ＧａＡｓ層と、ｎ−Ａｌ_０．９Ｇａ_０．１Ａｓ層とｎ−ＧａＡｓ層との間に図２のようにＡｌ組成を一方の値から他方の値に線形に変化させた厚さ４０ｎｍのｎ−ＡｌＧａＡｓ線形組成傾斜層（中間層）とが、周期的に積層されることによって構成されている。
【０１００】
ここで、各層の厚さは、実施例１と同様に、組成傾斜層における光の位相変化に応じた厚さを減じ、ブラッグ反射器の多重反射の位相条件が満たされる様に選んでいる。ここで、組成傾斜層の厚さ４０ｎｍは、分布ブラッグ反射器の反射波長λ（＝１．３μｍ）に対し、２０＜ｔ≦（５０λ−１５）［ｎｍ］の範囲に選んでおり、高い反射率を維持したまま、ヘテロ界面による静電容量を従来に比べて低減することができた。よって、面発光レーザ素子等の共振器ミラーとして、好適なｎ型分布ブラッグ反射器を得ることができた。
【０１０１】
（実施例３）
図３は、実施例３として第５，第１２の実施形態の面発光半導体レーザ素子の一例を説明するための図である。図３の面発光半導体レーザ素子は、ＧａＩｎＮＡｓを活性層とした１．３μｍ帯の面発光半導体レーザ素子であり、トリメチルアルミニウム（ＴＭＡ），トリメチルガリウム（ＴＭＧ），トリメチルインジウム（ＴＭＩ），アルシン（ＡｓＨ_３）ガスを原料とし、ＭＯＣＶＤ法によって結晶成長がなされている。この際、活性層の窒素原料には、ジメチルヒドラジン（ＤＭＨｙ）を用いることができる。また、ｐ型ドーパントにはＣＢｒ_４を用い、ｎ型ドーパントにはＨ_２Ｓｅを用いることができる。
【０１０２】
図３の面発光半導体レーザ素子は、次のようにして作製される。すなわち、先ず、ｎ−ＧａＡｓ基板上に、ｎ−ＧａＡｓバッファー層の結晶成長を行った後、ＡｌＡｓ／ＧａＡｓを１対のペアとしたｎ型半導体分布ブラッグ反射器３６ペアの結晶成長を行なう。この際、ｎ−ＡｌＡｓ／ＧａＡｓ半導体分布ブラッグ反射器の各へテロ界面には、実施例１に示したように、一方から他方の組成へＡｌ組成を線形に変化させた厚さ３０ｎｍのｎ−ＡｌＧａＡｓ線形組成傾斜層を中間層（半導体層）として設ける。
【０１０３】
このようにｎ−ＡｌＡｓ／ＧａＡｓ半導体分布ブラッグ反射器を形成した後、ＧａＡｓ共振器スペーサー層，ＧａＩｎＮＡｓ／ＧａＡｓ多重量子井戸構造（活性層），ＧａＡｓ共振器スペーサー層，Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとした２２ペアのｐ型半導体分布ブラッグ反射器を順次に形成する。ここで、１対目のｐ型半導体分布ブラッグ反射器の界面には厚さ３０ｎｍのＡｌＡｓ選択酸化層を設けている。更に、ｐ型半導体分布ブラッグ反射器の各界面には、素子抵抗を低減するために、一方の組成から他方の組成へＡｌ組成を線形に変化させた線形組成傾斜層（厚さ３０ｎｍ）を設けている。また、ｐ型半導体分布ブラッグ反射器の再表面層となるＧａＡｓ層の表面付近のドーピング密度を１×１０^１９ｃｍ^−３としてコンタクト層と兼用している。
【０１０４】
ここで、ｐ型半導体分布ブラッグ反射器及びｎ型半導体分布ブラッグ反射器を構成する各層の厚さは、組成傾斜層（中間層）を含めて、実施例１と同様に分布ブラッグ反射器の多重反射の位相条件を満たすように調整されており、ＡｌＡｓ選択酸化層に接したＡｌ_０．８Ｇａ_０．２Ａｓ層の厚さも同様に調整が行われている。また、この面発光半導体レーザ素子の、活性層と２つの共振器スペーサー層における発振光の位相変化は２πに等しく、１λキャビティーを形成している。また、活性層は１λキャビティーの中央、つまり光の定在波の腹となる位置に配置されている。
【０１０５】
次に、公知の写真製版，ドライエッチング法により、素子部となる領域を残し、ｐ−ＧａＡｓコンタクト層の表面からｎ半導体分布ブラッグ反射器に接したＧａＡｓ共振器スペーサー層の途中までの各層をメサ形状に加工（ドライエッチング除去）している。この際、素子部となるメサは３０μｍ×３０μｍの方形メサ形状としている。
【０１０６】
次に、８０℃に加熱した純水を窒素ガスによりバブリングして得られた雰囲気中で加熱を行い、ＡｌＡｓ選択酸化層のエッチング側面から素子中央部に向かい、横方向から選択酸化を行い電流狭窄構造としている。このとき、電流通路となる領域の大きさは５μｍ×５μｍとした。
【０１０７】
次に、メサ部をポリイミド等の絶縁性樹脂によって埋め込んだ後、電極材料の蒸着及びリフトオフを行ない、素子上面の光出射部に開口を有するｐ側電極を形成する。次に、基板の裏面にｎ側電極を形成し、図３の面発光半導体レーザ素子を作製することができる。
【０１０８】
図３の面発光半導体レーザ素子では、ｐ型半導体分布ブラッグ反射器及びｎ型半導体分布ブラッグ反射器の両方のヘテロ界面の間に組成傾斜層が設けられている。ｐ型半導体分布ブラッグ反射器中に設けられている組成傾斜層は、公知技術のように、素子抵抗を低減させるためのものである。また、ｎ型半導体分布ブラッグ反射器中にｎ型組成傾斜層を設けることによって、従来の素子と比べて素子の静電容量を飛躍的に低減することができる。すなわち、図３の面発光半導体レーザ素子は、ｎ型組成傾斜層がｎ型半導体分布ブラッグ反射器に設けられることによって、ｎ型半導体分布ブラッグ反射器を構成するＡｌＡｓとＧａＡｓの界面におけるスパイク，ノッチ等のポテンシャル分布が平滑化される。これにより、キャリアの蓄積，空乏が抑制されて、静電容量が飛躍的に低減され、高速変調に好適な構造となる。実際、図３の面発光半導体レーザ素子は、１０Ｇｂｐｓ以上の高速変調を容易に行うことができた。
【０１０９】
また、図３の面発光半導体レーザ素子は、活性層材料をＧａＩｎＮＡｓとしており、ＧａＡｓ基板上にＡｌ（Ｇａ）Ａｓ／ＧａＡｓによる特性の優れた半導体分布ブラッグ反射器を用いて、１．３μｍで発振する面発光半導体レーザ素子を提供することができた。すなわち、ＧａＩｎＮＡｓ混晶は、ＧａＡｓ等のバリア層、又は共振器スペーサー層との伝導帯バンド不連続量が大きく、活性層への電子の閉じ込め効果が高いので、高温まで安定な発振が得られる。また、１．３μｍ帯は、石英ファイバの零分散帯にあたり、同シングルモードファイバを用いることにより、高速通信が可能である。上述のように、実際に、図３の面発光半導体レーザ素子では、高速変調が可能であり、石英シングルモードファイバと組み合わせることによって、高速通信を容易に行うことが可能となる。
【０１１０】
（実施例４）
図４は、実施例４として第６，第８の実施形態の面発光半導体レーザ素子の一例を説明するための図である。図４の面発光半導体レーザ素子は、ＧａＩｎＡｓ／ＧａＡｓ多重量子井戸を活性層とする０．９８μｍ帯の面発光半導体レーザ素子であり、ｎ−ＧａＡｓ基板上にＭＯＣＶＤ法によって実施例３と同様に結晶成長がなされている。
【０１１１】
すなわち、図４の面発光半導体レーザ素子では、Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとした３６ペアのｎ型半導体分布ブラッグ反射器を結晶成長した後、Ａｌ_０．１５Ｇａ_０．８５Ａｓ共振器スペーサー層，ＧａＩｎＡｓ／ＧａＡｓ多重量子井戸構造，Ａｌ_０．１５Ｇａ_０．８５Ａｓ共振器スペーサー層，Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとした２２ペアのｐ型半導体分布ブラッグ反射器が順次に形成されている。
【０１１２】
ここで、図４の面発光半導体レーザ素子では、ｐ型半導体分布ブラッグ反射器中のみに、素子抵抗を低減させるための厚さ３０ｎｍの線形組成傾斜層が設けられている。また、更に、ｐ型半導体分布ブラッグ反射器には、実施例３と同様にＡｌＡｓ選択酸化層が設けられている。
【０１１３】
また、半導体分布ブラッグ反射器を構成する層の厚さは、発振波長である０．９８μｍの光に対し、分布ブラッグ反射器の多重反射の位相条件を満たすように、組成傾斜層及び選択酸化層の厚さを考慮して設定されている。
【０１１４】
ところで、この実施例４の面発光半導体レーザ素子は、ｎ型半導体分布ブラッグ反射器が基板表面までエッチング（ドライエッチング）されていることによって（すなわち、ｎ型半導体分布ブラッグ反射器がメサ形状にエッチング加工されていることによって）、ｎ型半導体分布ブラッグ反射器における電子の通路がメサ領域に限定されている。
【０１１５】
本来、この面発光半導体レーザ素子では、ドライエッチングは、選択酸化層の横方向の酸化を行うために行われる工程であって、従来の面発光半導体レーザ素子では、共振器スペーサー層の途中、もしくは、２〜３ペア程度のｎ型半導体分布ブラッグ反射器の途中までがエッチング除去されている。従って、従来の面発光半導体レーザ素子においては、ｎ型半導体分布ブラッグ反射器は電子に対する狭窄構造とはなっておらず、電子電流は、基板の裏面全体に設けられたｎ側電極から、メサ径よりも広いｎ型半導体分布ブラッグ反射器の領域を通って活性領域に注入される。この際、電子電流の通路となる領域のｎ型半導体分布ブラッグ反射器の界面における静電容量が、面発光半導体レーザ素子の容量として寄与する。
【０１１６】
従って、この実施例４のように、ｎ型半導体分布ブラッグ反射器をエッチングによってメサ径と同程度にエッチング加工することにより（メサ形状に加工することにより）、静電容量を低減することができる。すなわち、実施例４の面発光半導体レーザ素子の静電容量は、従来の素子に比べて小さく、高速変調に適している。実際、実施例４の面発光半導体レーザ素子は、１０Ｇｂｐｓを超える高速変調を容易に行うことができた。
【０１１７】
また、図４の面発光半導体レーザ素子のｎ型半導体分布ブラッグ反射器に、図５の構成のｎ型半導体分布ブラッグ反射器を用いることにより、面発光半導体レーザ素子の容量をより一層低減することが可能となる。すなわち、図５のｎ型半導体分布ブラッグ反射器は、図１のｎ型半導体分布ブラッグ反射器と同様に、ｎ−Ａｌ_０．８Ｇａ_０．２Ａｓ層とｎ−ＧａＡｓ層のヘテロ界面に一方から他方の組成へＡｌ組成を線形に変化させたｎ−ＡｌＧａＡｓ線形組成傾斜層（中間層）が設けられたものであり、図５のｎ型半導体分布ブラッグ反射器を図４の面発光半導体レーザ素子のｎ型半導体分布ブラッグ反射器として用いることによって、ヘテロ界面による静電容量を飛躍的に低減できるとともに、電子電流の通路が狭窄されて静電容量として寄与する領域の面積を低減することができ、これにより、更に素子容量を低減させることが可能となる。従って、図４の面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器に図５のｎ型半導体分布ブラッグ反射器を用いることで、非常に高速変調に好適な素子構造が得られる。このような面発光半導体レーザ素子では、１０Ｇｂｐｓ以上の高速変調を容易に行うことができた。
【０１１８】
（実施例５）
図６は、実施例５として第７，第８の実施形態の面発光半導体レーザ素子の一例を説明するための図である。図６の面発光半導体レーザ素子は、ＧａＩｎＡｓ／ＧａＡｓ多重量子井戸を活性層とする０．９８μｍ帯の面発光半導体レーザ素子であり、ｎ−ＧａＡｓ基板上にＭＯＣＶＤによって実施例３と同様に結晶成長がなされている。
【０１１９】
すなわち、図６の面発光半導体レーザ素子では、ＡｌＡｓ／ＧａＡｓを１対のペアとした３６ペアのｎ型半導体分布ブラッグ反射器を結晶成長した後、Ａｌ_０．１５Ｇａ_０．８５Ａｓ共振器スペーサー層，ＧａＩｎＡｓ／ＧａＡｓ多重量子井戸構造，Ａｌ_０．１５Ｇａ_０．８５Ａｓ共振器スペーサー層，Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとした２２ペアのｐ型半導体分布ブラッグ反射器が順次に形成されている。
【０１２０】
ここで、図６の面発光半導体レーザ素子では、ｐ型半導体分布ブラッグ反射器中のみに、素子抵抗を低減させるための厚さ３０ｎｍの線形組成傾斜層が設けられている。また、ｐ型半導体分布ブラッグ反射器には、実施例３と同様にＡｌＡｓ選択酸化層が設けられている。
【０１２１】
また、半導体分布ブラッグ反射器を構成する層の厚さは、発振波長である０．９８μｍの光に対し、分布ブラッグ反射器の多重反射の位相条件を満たすように、組成傾斜層及び選択酸化層の厚さを考慮して設定されている。
【０１２２】
ところで、この実施例５の面発光半導体レーザ素子は、実施例３と同様にｐ−ＧａＡｓコンタクト層の表面からｎ半導体分布ブラッグ反射器に接したＧａＡｓ共振器スペーサー層の途中までの各層をメサ形状に加工（ドライエッチング除去）した後、ドライエッチングに用いたレジストパターンをマスクとしてｎ型半導体分布ブラッグ反射器に水素イオン注入を行ない、注入が行われたｎ型半導体分布ブラッグ反射器の全領域が高抵抗化されたものとなっている。すなわち、メサ部以外（共振領域以外）のｐ型半導体分布ブラッグ反射器が高抵抗化されている。そして、このようなイオン注入の後、実施例３と同様にＡｌＡｓ層の選択酸化により酸化狭窄構造を設けた後、絶縁性樹脂による埋め込み、ｐ側電極，ｎ側電極の形成がなされている。
【０１２３】
実施例４で説明したように、従来の面発光半導体レーザ素子においては、ｎ型半導体分布ブラッグ反射器は電子に対しての狭窄構造とはなっておらず、電子の電流通路は、ｎ型半導体分布ブラッグ反射器のところで、メサ径よりも広い領域に広がっており、面発光半導体レーザ素子の容量として、このｎ型半導体分布ブラッグ反射器の領域におけるヘテロ界面の静電容量の寄与がある。
【０１２４】
これに対し、この実施例５の面発光半導体レーザ素子のように、水素イオン注入によりｎ型半導体分布ブラッグ反射器に高抵抗化領域を設け、電子電流通路を狭窄することによって、不必要な静電容量を低減することが可能となる。従って、この実施例５の面発光半導体レーザ素子は、高速変調に適した構造となっている。また、ｎ型半導体分布ブラッグ反射器中における電子電流の狭窄構造を水素イオン注入による高抵抗化によって形成しているので、メサ高さを不必要に高くせずに済み、素子の物理的強度も高く、また絶縁性樹脂による埋め込みも容易である。また、実施例５の面発光半導体レーザ素子では、活性領域とエッチング表面との距離が近いので、基板側への放熱を低下させずに済み、熱による出力の低下の影響が少ない。実際、実施例５の面発光半導体レーザ素子では、ｎ型半導体分布ブラッグ反射器の静電容量を低減できたことによって、１０Ｇｂｐｓを超える高速変調を容易に実現することができた。
【０１２５】
また、図６の面発光半導体レーザ素子のｎ型半導体分布ブラッグ反射器に、図７の構成のｎ型半導体分布ブラッグ反射器を用いることにより、面発光半導体レーザ素子の容量をより一層低減することが可能となる。すなわち、図７のｎ型半導体分布ブラッグ反射器は、図１のｎ型半導体分布ブラッグ反射器と同様に、ｎ−ＡｌＡｓ層とｎ−ＧａＡｓ層のヘテロ界面に一方から他方の組成へＡｌ組成を線形に変化させたｎ−ＡｌＧａＡｓ線形組成傾斜層（中間層）が設けられたものであり、図７のｎ型半導体分布ブラッグ反射器を図６の面発光半導体レーザ素子のｎ型半導体分布ブラッグ反射器として用いることによって、ヘテロ界面による静電容量を飛躍的に低減できるとともに、電子電流の通路が狭窄されて静電容量として寄与する領域の面積を低減することができ、これにより、更に素子容量を低減させることが可能となる。従って、図６の面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器に図７のｎ型半導体分布ブラッグ反射器を用いることで、非常に高速変調に好適な素子構造が得られる。このような面発光半導体レーザ素子では、１０Ｇｂｐｓ以上の高速変調を容易に行うことができた。
【０１２６】
なお、上述した各実施例（実施例１，実施例３，実施例４，実施例５）では、ｎ型半導体基板上に結晶成長を行った面発光半導体レーザ素子を示したが、本発明の面発光半導体レーザ素子としては、ｎ型半導体基板のかわりに、ｐ型半導体基板を用いることも可能である。
【０１２７】
図８は、例えば実施例３の面発光半導体レーザ素子をｐ型半導体基板上に実現した例を示す図であり、図８の面発光半導体レーザ素子は、ｐ−ＧａＡｓ基板上に、ＭＯＣＶＤ法によって同様に結晶成長がなされたものである。すなわち、図８の面発光半導体レーザ素子は、先ず、ｐ−ＧａＡｓ基板上に、ｐ−ＧａＡｓバッファー層の結晶成長を行った後、Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとしたｐ型半導体分布ブラッグ反射器３６ペアの結晶成長を行い、ＧａＡｓ共振器スペーサー層，ＧａＩｎＮＡｓ／ＧａＡｓ多重量子井戸活性層，ＧａＡｓスペーサー層，Ａｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓを１対のペアとしたｎ型半導体分布ブラッグ反射器２６ペアを順次に結晶成長して形成されている。
【０１２８】
ここで、ｐ型半導体分布ブラッグ反射器の各へテロ界面には、電気抵抗を低減するための線形組成傾斜層（厚さ３０ｎｍ）が、半導体分布ブラッグ反射器の多重反射の位相条件を満たすように設けられている。また、活性層に一番近いＡｌ_０．８Ｇａ_０．２Ａｓ／ＧａＡｓのヘテロ界面には、ＡｌＡｓ選択酸化層が同様に位相条件を考慮して設けられている。更に、ｎ型半導体分布ブラッグ反射器には、本発明のｎ型半導体分布ブラッグ反射器が用いられている。すなわち、ｎ型半導体分布ブラッグ反射器の各へテロ界面には、静電容量を低減するための線形組成傾斜層（厚さが３０ｎｍ）が中間層（半導体層）として設けられている。
【０１２９】
図８の面発光半導体レーザ素子は、上記のような結晶成長の後、実施例３と同様に、ドライエッチング、選択酸化、絶縁性樹脂による埋め込み、電極形成が行われている。但し、ドライエッチング工程では、ｐ型半導体分布ブラッグ反射器中のＡｌＡｓ選択酸化層を酸化させるために、ｐ型半導体分布ブラッグ反射器の途中までエッチングが行われている。
【０１３０】
図８の面発光半導体レーザ素子では、実施例３と同様に、ｎ型半導体分布ブラッグ反射器の静電容量が低減されたことにより、高速変調に好適な構造となっており、１０Ｇｂｐｓを超える変調を容易に行うことができた。
【０１３１】
また、図９は面発光半導体レーザ素子の他の構成例を示す図である。図９の面発光半導体レーザ素子は、図８の面発光半導体レーザ素子と同様に作製がなされたものであり、ｐ型半導体分布ブラッグ反射器中には、電気抵抗を低減させるための組成傾斜層が設けられ、また、ｎ型半導体分布ブラッグ反射器中には、静電容量を低減させるための組成傾斜層（中間層）が設けられている。ただし、図９の面発光半導体レーザ素子は、メサ部のドライエッチング工程の後に、実施例５と同様に水素イオン注入が行われており、ｐ型半導体分布ブラッグ反射器のメサ部以外（共振領域以外）の領域が高抵抗化されている。従って、正孔の電流通路をメサ径程度に狭窄したことによって、ｐ型半導体分布ブラッグ反射器による静電容量も低減され、図８の素子に比べて更に高速変調に好適な構造となっている。
【０１３２】
また、上述した各実施例（実施例１，実施例３，実施例４，実施例５）では、面発光半導体レーザ素子の結晶成長をＭＯＣＶＤ法によって行なっているが、ＭＯＣＶＤ法以外の成長方法を用いて結晶成長を行なうこともできる。また、半導体分布ブラッグ反射器を構成する屈折率の異なる２種の半導体層の間に設けられる中間層（２種の半導体層の間の屈折率（禁則帯幅）を有する半導体層）として、線形組成傾斜層が用いられるとしたが、中間層としては、この他にも、非線形に組成が変化しているものを用いることもできるし、また、屈折率が異なる単層または複数の層によって構成されたものを用いることもできる。
【０１３３】
（実施例６）
図１０は、実施例６として第１３の実施形態の面発光レーザアレイの一例を説明するための図である。図１０の面発光レーザアレイは、上述した本発明の面発光半導体レーザ素子を２次元に３×３個集積したモノリシックレーザアレイとなっている。図１０の面発光レーザアレイでは、個々の面発光半導体レーザ素子を独立に駆動するために、個別にｐ電極配線が設けられている。図１０の面発光レーザアレイは、実施例１，実施例３乃至実施例５と同様の手順，方法で作製されている。
【０１３４】
図１０の面発光レーザアレイでは、この面発光レーザアレイを構成する個々の面発光半導体レーザ素子は、いずれも、ｎ型半導体分布ブラッグ反射器による静電容量が低減されており、従って、この面発光レーザアレイは、非常に高速変調に好適な構造となっており、実際、高速変調が可能であった。
【０１３５】
（実施例７）
図１１は、実施例７として第１４の実施形態の面発光レーザモジュールの一例を説明するための図である。図１１の面発光レーザモジュールは、シリコン基板上に、１次元モノリシック面発光レーザアレイと、マイクロレンズアレイと、ファイバアレイ（石英シングルモードファイバ）とが実装されて構成されている。
【０１３６】
ここで、面発光レーザアレイには、第１３の実施形態の面発光レーザアレイがファイバに対向して設けられており、この面発光レーザアレイは、マイクロレンズアレイを介して、シリコン基板に形成されたＶ溝に実装されている石英シングルモードファイバと結合している。この面発光レーザアレイの発振波長は１．３μｍ帯であり、石英シングルモードファイバを用いることで、高速光並列伝送を行なうことができる。
【０１３７】
また、図１１の面発光レーザモジュールの光源として、第１３の実施形態の面発光レーザアレイを用いることにより、高速変調が可能となり、高速伝送が可能な面発光レーザモジュールを得ることができる。
【０１３８】
（実施例８）
図１２は、第１５の実施形態の光インターコネクションシステムの一例としての並列光インターコネクションシステムを示す図である。図１２のインターコネクションシステムでは、機器１と機器２の間が光ファイバアレイ（石英シングルモードファイバアレイ）を用いて接続されている。ここで、送信側である機器１には、第１４の実施形態の面発光レーザアレイによる面発光レーザモジュールと、これの駆動回路とが備わっている。また、受信側である機器２には、フォトダイオードアレイモジュールと信号検出回路とが備わっている。
【０１３９】
図１２の光インターコネクションシステムでは、第１４の実施形態の面発光レーザモジュールを用いることで、高速光並列伝送が可能となる。また、面発光レーザモジュールには、ＧａＩｎＮＡｓを活性層とした面発光レーザアレイが用いられることで、環境温度の変化に対しても安定に発振が得られ、非常に信頼性の高いインターコネクションシステムを構成することができる。
【０１４０】
上述の例では、並列光インターコネクションシステムを例に説明したが、この他にも、単一素子を用いたシリアル伝送システムを構成することもできる。また、機器間の他にも、ボード間，チップ間，チップ内インターコネクションに適用することもできる。
【０１４１】
（実施例９）
図１３は、第１６の実施形態の光通信システムの実施例としての光ＬＡＮシステムを示す図である。図１３の光ＬＡＮシステムは、上述した本発明の面発光半導体レーザ素子または面発光レーザアレイまたは面発光レーザモジュールを用いて構成されている。
【０１４２】
すなわち、図１３の光ＬＡＮシステムでは、サーバーとコアスイッチとの間の光伝送の光源、および／または、コアスイッチと各スイッチとの間の光伝送の光源、および／または、スイッチと各端末との間の光伝送の光源に、上述した本発明の面発光半導体レーザ素子または面発光レーザアレイまたは面発光レーザモジュールが用いられている。また、各機器間は石英シングルモードファイバまたはマルチモードファイバによって結合を行っている。このような光ＬＡＮの物理層としては、例えば１０００ＢＡＳＥ−ＬＸ等のギガビットイーサネットが挙げられる。
【０１４３】
図１３の光ＬＡＮシステムでは、光伝送の光源に、上述した本発明の面発光半導体レーザ素子または面発光レーザアレイまたは面発光レーザモジュールが用いられることで、高速通信が可能となった。更に、ＧａＩｎＮＡｓを活性層とした本発明の面発光レーザでは、動作環境温度等、駆動条件の変化に対しても安定に発振が得られ、信頼性の高い光通信システムを構成することができる。
【０１４４】
【発明の効果】
以上に説明したように、請求項１記載の発明によれば、屈折率が異なる２種の半導体層が積層されているｎ型にドープされたｎ型半導体分布ブラッグ反射器において、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられているので、半導体へテロ界面の静電容量が低減されたｎ型半導体分布ブラッグ反射器を提供することができる。
【０１４５】
また、請求項２記載の発明によれば、中間層の厚さを２０ｎｍよりも厚くすることによって、ヘテロ界面の影響を大幅に低減し、ｎ型分布ブラッグ反射器の電流−電圧特性を改善することができるとともに、ヘテロ界面における静電容量を低減することができる。
【０１４６】
中間層によりヘテロ界面の容量が低減されるのは、中間層によってヘテロ界面におけるスパイク，ノッチ等のポテンシャル分布が平滑化され、界面におけるキャリアの蓄積，空乏化が抑制される為である。中間層を設けない場合には、ヘテロ界面に生じるスパイク，ノッチ形状のポテンシャル分布によってキャリア（電子）の蓄積，空乏化が生じ、測定条件による電流−電圧特性の変化、及びヘテロ障壁におけるキャリアのトンネル等が原因と考えられる電流−電圧特性の非線形性が生じるといった問題がある。更に、これに加えて、キャリアの空乏化にる静電容量の発生等も問題となる。しかし、ｎ型分布ブラッグ反射器の各界面に２０ｎｍ以上の厚さの中間層を設けた場合には、これらの問題を大幅に改善することができる。つまり、２０ｎｍよりも厚い中間層によって、測定条件による電流−電圧特性の変化、及び電流−電圧特性の非線形性は大幅に低減し、またヘテロ界面による静電容量を大幅に低減することができる。以上から、電気特性の優れたｎ型分布ブラッグ反射器を得ることができる。
【０１４７】
また、請求項３記載の発明によれば、中間層の厚さを３０ｎｍ以上の厚さとすることによって、ヘテロ界面の影響を更に効果的に低減し、ｎ型分布ブラッグ反射器の電流−電圧特性を改善することができるとともに、ヘテロ界面における静電容量を低減することができる。
【０１４８】
中間層によりヘテロ界面の容量が低減されるのは、中間層によって、ヘテロ界面におけるスパイク，ノッチ等のポテンシャルの分布が平滑化され、界面におけるキャリアの蓄積，空乏化が抑制される為であり、厚い中間層程、この作用は大きい。従って、特に中間層の厚さを３０ｎｍ以上とすることにより、ＣＷ測定とパルス測定との違いは殆ど無くなり、より効果的に前述の様な作用を得ることができる。以上の様に、電流−電圧特性の変化、及び電流−電圧特性の非線形性をより効果的に低減し、また同様にヘテロ界面による静電容量をより効果的に低減することができる。以上から、電気特性の優れたｎ型分布ブラッグ反射器を得ることができる。
【０１４９】
また、請求項４記載の発明によれば、請求項１記載のｎ型半導体分布ブラッグ反射器において、前記中間層の厚さｔ［ｎｍ］が、分布ブラッグ反射器の反射波長λ［μｍ］に対して、２０＜ｔ≦（５０λ−１５）［ｎｍ］の範囲であるので、高い反射率を維持したまま、ヘテロ界面の影響が低減された、電気特性の優れたｎ型分布ブラッグ反射器を得ることができる。すなわち、分布ブラッグ反射器は、これを構成する半導体層の屈折率差が大きい程、また界面が急峻である程、高い反射率を得ることができる。従って、中間層の厚さが厚くなるのに対応し、反射率は次第に低下する傾向がある。従って、中間層の厚さを厚くし過ぎると、分布ブラッグ反射器の反射率は急激に低下する。しかし、ヘテロ界面を平坦にする効果は、中間層の厚さが厚い程有効に得られる。よって中間層の厚さとして、これらを両立する最適な範囲があることが分かる。つまり、最適な中間層の厚さの範囲とし、中間層の厚さを分布ブラッグ反射器の反射波長λ［μｍ］に対し、２０＜ｔ≦（５０λ−１５）［ｎｍ］に選ぶことによって、高い反射率を維持したまま、ヘテロ界面の影響が低減された、電気特性の優れたｎ型分布ブラッグ反射器を得ることができる。
【０１５０】
また、請求項５記載の発明によれば、請求項１乃至請求項４のいずれか一項に記載のｎ型半導体分布ブラッグ反射器が用いられていることを特徴とする面発光半導体レーザ素子であるので、静電容量が低減され、高速変調が可能な面発光半導体レーザ素子を提供することができる。
【０１５１】
また、請求項６記載の発明によれば、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器がメサ形状に加工されているので、静電容量が低減され、高速変調が可能な面発光半導体レーザ素子を提供することができる。
【０１５２】
また、請求項７記載の発明によれば、活性層を挟んでｎ型半導体分布ブラッグ反射器とｐ型半導体分布ブラッグ反射器とが設けられている面発光半導体レーザ素子において、ｎ型半導体分布ブラッグ反射器の共振領域以外の領域が高抵抗化されているので、静電容量が低減され、高速変調が可能な面発光半導体レーザ素子を提供することができる。
【０１５３】
また、請求項８記載の発明によれば、請求項６または請求項７記載の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられているので、静電容量が低減され、高速変調が可能な面発光半導体レーザ素子を提供することができる。
【０１５４】
また、請求項９記載の発明によれば、請求項６または請求項７記載の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さが２０［ｎｍ］よりも厚いので、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。すなわち、請求項１，請求項２の効果で説明した様に、前記の半導体層をヘテロ界面に設けることによって、中間層を設けない場合に比べて、ヘテロ界面におけるポテンシャルの分布が平滑化され、キャリアの空乏，蓄積が低減し、空乏化によって生じる静電容量を飛躍的に低減することができる。更に、請求項６，請求項７の様に、ｎ型半導体分布ブラッグ反射器のエッチング、及び高抵抗化により電子の通路をメサ領域内に限定することによって、容量として実効的に寄与する半導体分布ブラッグ反射器の面積を低減することができる。従って、請求項９の様にこれらを併せて用いることにより、更に効果的に素子の静電容量を低減することが可能であり、非常に高速変調に適した構造を得ることが可能である。請求項９による素子は、以上の様にｎ型半導体分布ブラッグ反射器の静電容量が低減したことによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【０１５５】
また、請求項１０記載の発明によれば、請求項６または請求項７記載の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さが３０［ｎｍ］以上の厚さであるので、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。すなわち、請求項１，請求項２の効果で説明した様に、前記の半導体層をヘテロ界面に設けることによって、十分にヘテロ界面におけるポテンシャルの分布を平滑化することが可能であり、キャリアの空乏，蓄積が低減し、空乏化によって生じる静電容量を更に飛躍的に低減することができる。更に、請求項６，請求項７の様に、ｎ型半導体分布ブラッグ反射器のエッチング、及び高抵抗化により電子の通路をメサ領域内に限定することによって、容量として実効的に寄与する半導体分布ブラッグ反射器の面積を低減することができる。従って、請求項１０の様にこれらを併せて用いることにより、更に効果的に素子の静電容量を低減することが可能であり、非常に高速変調に適した構造を得ることが可能である。請求項１０による素子は、以上の様にｎ型半導体分布ブラッグ反射器の静電容量が低減したことによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【０１５６】
また、請求項１１記載の発明によれば、請求項６または請求項７記載の面発光半導体レーザ素子において、前記ｎ型半導体分布ブラッグ反射器は、屈折率が異なる２種の半導体層の間に、前記２種の半導体層の間の屈折率を有する中間層が設けられ、前記中間層の厚さｔ［ｎｍ］が、分布ブラッグ反射器の反射波長λ［μｍ］に対して、２０＜ｔ≦（５０λ−１５）［ｎｍ］の範囲であるので、電子電流の通路を限定し、静電容量に寄与するｎ型半導体分布ブラッグ反射器の面積を低減でき、更に、ｎ型半導体分布ブラッグ反射器のヘテロ界面の静電容量を低減し、高速変調が可能となる。すなわち、請求項１，請求項２，請求項３の効果で説明した様に、前記の半導体層をヘテロ界面に設けることによって、ヘテロ界面におけるポテンシャルの分布が平滑化され、キャリアの空乏，蓄積が低減し、空乏化によって生じる静電容量を飛躍的に低減することができる。また、中間層の厚さを上記の範囲に選ぶことによって、ｎ型分布ブラッグ反射器の反射率を高く維持することができ、発振閾値電流の低い面発光レーザ素子を得ることができる。
【０１５７】
更に、請求項６，請求項７の様にｎ型半導体分布ブラッグ反射器のエッチング及び高抵抗化により電子の通路をメサ領域内に限定することによって、容量として実効的に寄与する半導体分布ブラッグ反射器の面積を低減することができる。従って、請求項１１の様にこれらを併せて用いることにより、更に効果的に素子の静電容量を低減することが可能であり、非常に高速変調に適した構造を得ることが可能である。請求項１１による素子は、以上の様にｎ型半導体分布ブラッグ反射器の静電容量が低減したことによって、１０Ｇｂｐｓ以上の高速変調を容易に行うことが可能となる。
【０１５８】
また、請求項１２記載の発明によれば、請求項５乃至請求項１１のいずれか一項に記載の面発光半導体レーザ素子において、活性層は、ＩＩＩ族材料とＶ族材料とにより構成されており、活性層のＩＩＩ族材料が、Ｇａ，Ｉｎのいずれか、または、全てであり、活性層のＶ族材料が、Ａｓ，Ｎ，Ｓｂのいずれか、または、全てであるので、静電容量が低減され、高速変調が可能な長波長帯の面発光半導体レーザ素子を提供することができる。
【０１５９】
また、請求項１３記載の発明によれば、請求項５乃至請求項１２のいずれか一項に記載の面発光半導体レーザ素子によって構成されていることを特徴とする面発光レーザアレイであるので、静電容量が低減され、高速変調が可能な面発光レーザアレイを提供することができる。
【０１６０】
また、請求項１４記載の発明によれば、請求項５乃至請求項１２のいずれか一項に記載の面発光半導体レーザ素子、または、請求項１３記載の面発光レーザアレイが用いられていることを特徴とする面発光レーザモジュールであるので、高速な光通信，光伝送が可能な面発光レーザモジュールを提供することができる。
【０１６１】
また、請求項１５記載の発明によれば、請求項５乃至請求項１２のいずれか一項に記載の面発光半導体レーザ素子、または、請求項１３記載の面発光レーザアレイ、または、請求項１４記載の面発光レーザモジュールを用いて構成された光インターコネクションシステムであるので、高速，大容量の光伝送が可能な光インターコネクションシステムを提供することができる。
【０１６２】
また、請求項１６記載の発明によれば、請求項５乃至請求項１２のいずれか一項に記載の面発光半導体レーザ素子、または、請求項１３記載の面発光レーザアレイ、または、請求項１４記載の面発光レーザモジュールを用いて構成された光通信システムであるので、高速，大容量の光伝送が可能な光通信システムを提供することができる。
【図面の簡単な説明】
【図１】第１の実施形態のｎ型半導体分布ブラッグ反射器の一例を説明するための図である。
【図２】組成傾斜層の一例を示す図である。
【図３】第２，第６の実施形態の面発光半導体レーザ素子の一例を説明するための図である。
【図４】第３，第５の実施形態の面発光半導体レーザ素子の一例を説明するための図である。
【図５】ｎ型半導体分布ブラッグ反射器の一例を示す図である。
【図６】第４，第５の実施形態の面発光半導体レーザ素子の一例を説明するための図である。
【図７】ｎ型半導体分布ブラッグ反射器の一例を示す図である。
【図８】実施例２の面発光半導体レーザ素子をｐ型半導体基板上に実現した例を示す図である。
【図９】面発光半導体レーザ素子の他の構成例を示す図である。
【図１０】第７の実施形態の面発光レーザアレイの一例を説明するための図である。
【図１１】第８の実施形態の面発光レーザモジュールの一例を説明するための図である。
【図１２】第９の実施形態の光インターコネクションシステムの一例としての並列光インターコネクションシステムを示す図である。
【図１３】第１０の実施形態の光通信システムの実施例としての光ＬＡＮシステムを示す図である。
【図１４】ヘテロ界面が素子特性に与える影響を示すための電流―電圧特性を示す図である。
【図１５】ＡｌＡｓ／ＧａＡｓからなるｎ型半導体分布ブラッグ反射器を含む素子を示す図である。
【図１６】図１５と同様の構造の素子において、ｎ型半導体分布ブラッグ反射器のＡｌＡｓ／ＧａＡｓの各界面に中間層として線形組成傾斜層を設けた場合の電流―電圧特性を示す図である。
【図１７】各波長帯において、ＡｌＡｓ／ＧａＡｓよりなる分布ブラッグ反射器の組成傾斜層の厚さに対する反射率変化の微係数を示す図である。
【図１８】第３の実施形態のｎ型半導体分布ブラッグ反射器の一例を説明するための図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an n-type semiconductor distributed Bragg reflector, a surface emitting semiconductor laser device, a surface emitting laser array, a surface emitting laser module, an optical interconnection system, and an optical communication system.
[0002]
[Prior art]
Conventionally, a distributed Bragg reflector (DBR) having reflection bands in the 0.85 μm band and 0.98 μm band, and a surface-emitting semiconductor laser device in the same wavelength band using such a distributed Bragg reflector as a resonator mirror are known. Have been. The distributed Bragg reflector is formed by alternately laminating materials having different refractive indices to a thickness of 1/4 of the wavelength of light in a medium, and utilizing multiple reflection of a light wave at an interface, is 99.9% or more. It is possible to obtain a very high reflectance.
[0003]
Further, the surface emitting semiconductor laser device has a low oscillation threshold current, can operate at high speed, and can be easily integrated two-dimensionally. Therefore, the surface emitting semiconductor laser device is suitable as a light source for optical interconnection and image processing systems. I have. The surface emitting semiconductor laser device requires a resonator mirror having a high reflectance of 99% or more because the region where optical gain is generated is only a part of the resonator region and the resonator length is short. A distributed Bragg reflector is preferred as the resonator mirror.
[0004]
As a material of the distributed Bragg reflector, for example, a semiconductor material or a dielectric material can be mentioned. In particular, a semiconductor distributed Bragg reflector made of a semiconductor material can be energized and is applied to a laser element such as a surface emitting semiconductor laser. Are suitable.
[0005]
Conventionally, as such a surface emitting semiconductor laser device, 0.85 μm band and 0.98 μm band devices made of an AlGaAs-based material using GaAs as a substrate are known. In this material system, a semiconductor distribution Bragg made of an AlGaAs material is used. A reflector is used as a resonator mirror.
[0006]
A semiconductor distributed Bragg reflector made of an AlGaAs-based material is composed of two types of AlGaAs layers having different Al compositions, a semiconductor layer having a large Al composition (for example, an AlAs layer) is used as a low refractive index layer, and a high refractive index is used. As the layer, a semiconductor layer having a small Al composition (for example, a GaAs layer) is used. In a typical example of a surface emitting semiconductor laser device, a p-type and n-type doped semiconductor distributed Bragg reflector is provided, sandwiching an active layer, for confining light waves and injecting carriers into the active region. ing.
[0007]
However, among these two types of semiconductor distributed Bragg reflectors, the p-type semiconductor distributed Bragg reflector has particularly high electric resistance due to the influence of the heterointerface due to the two types of semiconductor layers having different Al compositions. That is the problem. Conventionally, in order to reduce the electric resistance of a p-type semiconductor distributed Bragg reflector, for example, in a surface emitting semiconductor laser device in a 0.98 μm band or the like, a document “Photonics Technology, Letters, Letters, Vol. Pp. 234-236, Photonics Technology Letters Vol. 4, No. 12, 1992, pp. 1325-1327, etc., two different types of Al constituents constituting a distributed Bragg reflector. It is known to provide a hetero-barrier buffer layer such as a composition gradient layer having an intermediate Al composition between these layers.
[0008]
[Problems to be solved by the invention]
On the other hand, the n-type semiconductor distributed Bragg reflector has much lower resistance than the p-type semiconductor distributed Bragg reflector, and is considered to have little influence on device characteristics (eg, the characteristics of a surface emitting semiconductor laser device). Detailed examination was not carried out.
[0009]
However, in the n-type semiconductor distributed Bragg reflector, carriers are accumulated and depleted at the hetero interface of two different semiconductors due to the effect of band discontinuity of the semiconductor material, and the characteristics thereof are significantly different from those of the bulk semiconductor. In particular, a depletion layer having a reduced carrier density has a contribution to a capacitance component, and when a device (for example, a surface emitting semiconductor laser device) is pulse-driven or when high-speed modulation is performed, electrical characteristics and the like are reduced. This may cause a limitation on element response characteristics. In addition, there is a problem that a current-voltage characteristic becomes non-linear due to the influence of the hetero interface, and the current-voltage characteristic changes in response to a difference in element driving conditions.
[0010]
As described above, in order to obtain a device having excellent characteristics (for example, a surface emitting semiconductor laser device), it is necessary to carry out a detailed study on the structure and electrical characteristics of an n-type semiconductor distributed Bragg reflector. No detailed examination was carried out regarding.
[0011]
The present invention provides an n-type semiconductor distributed Bragg reflector, a surface-emitting semiconductor laser device, a surface-emitting laser array, and a semiconductor-heterointerface that can affect the current-voltage characteristics and reduce the capacitance due to the heterointerface. It is an object to provide a surface emitting laser module, an optical interconnection system, and an optical communication system.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is an n-type doped n-type semiconductor distributed Bragg reflector in which two types of semiconductor layers having different refractive indices are stacked. An intermediate layer having a refractive index between the two types of semiconductor layers is provided between the two types of semiconductor layers.
[0013]
According to a second aspect of the present invention, in the n-type distributed Bragg reflector according to the first aspect, the thickness of the intermediate layer is greater than 20 [nm].
[0014]
The invention according to claim 3 is the n-type distributed Bragg reflector according to claim 1, wherein the thickness of the intermediate layer is 30 nm or more.
[0015]
According to a fourth aspect of the present invention, in the n-type semiconductor distributed Bragg reflector according to the first aspect, the thickness t [nm] of the intermediate layer is relative to a reflection wavelength λ [μm] of the distributed Bragg reflector. , 20 <t ≦ (50λ−15) [nm].
[0016]
According to a fifth aspect of the present invention, there is provided a surface emitting semiconductor laser device using the n-type semiconductor distributed Bragg reflector according to any one of the first to fourth aspects.
[0017]
According to a sixth aspect of the present invention, there is provided a surface emitting semiconductor laser device having an n-type semiconductor distributed Bragg reflector and a p-type semiconductor distributed Bragg reflector with an active layer interposed therebetween, wherein the n-type semiconductor distributed Bragg reflector is provided. The container is processed into a mesa shape.
[0018]
According to a seventh aspect of the present invention, there is provided a surface emitting semiconductor laser device having an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed therebetween, wherein the n-type distributed Bragg reflector is provided. Is characterized in that a region other than the resonance region is increased in resistance.
[0019]
According to an eighth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between two kinds of semiconductor layers is provided.
[0020]
According to a ninth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector has a structure in which the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between two types of semiconductor layers is provided, and the thickness of the intermediate layer is greater than 20 [nm].
[0021]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector has a structure in which the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between two types of semiconductor layers is provided, and the thickness of the intermediate layer is 30 nm or more.
[0022]
According to an eleventh aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector has a structure in which the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness t [nm] of the intermediate layer is 20 <t ≦ ([lambda]) with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector. 50 [lambda] -15) [nm].
[0023]
According to a twelfth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the fifth to eleventh aspects, the active layer is made of a group III material and a group V material, The group III material of the active layer is any or all of Ga and In, and the group V material of the active layer is any or all of As, N, Sb, and P. .
[0024]
According to a thirteenth aspect of the present invention, there is provided a surface-emitting laser array comprising the surface-emitting semiconductor laser device according to any one of the fifth to eleventh aspects.
[0025]
According to a fourteenth aspect of the present invention, the surface emitting semiconductor laser device according to any one of the fifth to eleventh aspects or the surface emitting laser array according to the thirteenth aspect is used. Is a surface emitting laser module.
[0026]
According to a fifteenth aspect of the present invention, there is provided a surface emitting semiconductor laser device according to any one of the fifth to eleventh aspects, the surface emitting laser array according to the thirteenth aspect, or the surface emitting laser array according to the fourteenth aspect. This is an optical interconnection system configured using a surface emitting laser module.
[0027]
According to a sixteenth aspect of the present invention, there is provided a surface emitting semiconductor laser device according to any one of the fifth to eleventh aspects, the surface emitting laser array according to the thirteenth aspect, or the surface emitting laser array according to the fourteenth aspect. 1 is an optical communication system configured using a surface emitting laser module.
[0028]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0029]
First embodiment
According to the first embodiment of the present invention, in an n-type doped n-type semiconductor distributed Bragg reflector in which two types of semiconductor layers having different refractive indices are stacked, two types having different refractive indices (forbidden band widths) are used. An intermediate layer (semiconductor layer) having a refractive index between the two types of semiconductor layers is provided between the semiconductor layers.
[0030]
In the first embodiment, an n-type semiconductor distributed Bragg reflector is provided by providing an intermediate layer (semiconductor layer) having a refractive index between two types of semiconductor layers having different refractive indexes (forbidden band widths). Depletion of carriers at the hetero interface can be reduced, and the capacitance of the n-type distributed Bragg reflector can be reduced.
[0031]
That is, at a semiconductor heterointerface formed by semiconductor layers having different refractive indices (forbidden band widths) such as a semiconductor distributed Bragg reflector, spikes and heterojunctions occur at a heterointerface due to a difference in doping density and electron affinity of each semiconductor. A potential distribution called a notch is formed. For example, in a spike portion, a potential barrier against carriers is high, and carriers are depleted. Conversely, in a notch portion, carriers are accumulated because the potential barrier is low. Since the distribution of carriers at the hetero interface is not uniform, the element characteristics strongly reflect the influence of the hetero interface. As is well known, in a p-type semiconductor distributed Bragg reflector, the effective mass of holes, which are majority carriers, is large, so that it is strongly affected by spikes at the heterointerface and the element resistance becomes extremely high. In a distributed Bragg reflector, the effective mass of electrons, which are majority carriers, is smaller than that of holes. Therefore, there is little effect on element resistance and the like. Not considered in detail. However, as described above, at the hetero interface, carriers are depleted regardless of the conductivity type, resulting in capacitance.
[0032]
For example, the current-voltage characteristics in FIG. 14 will be described as showing the influence of the heterointerface on the device characteristics. The current-voltage characteristic of FIG. 14 is a comparison of the measurement result in CW (continuous waveform) and the measurement result in pulse for the device including the n-type semiconductor distributed Bragg reflector made of AlAs / GaAs shown in FIG. It is. Here, the device of FIG. 15 will be described in detail. In the device of FIG. 15, 35 pairs of n-type semiconductor distributed Bragg reflectors having a pair of AlAs / GaAs are crystal-grown on an n-GaAs substrate layer. Formed on the back surface of the n-GaAs substrate layer and the n-type semiconductor distributed Bragg reflector₂An ohmic electrode is provided on a portion where the insulating layer is removed (a portion where a stripe-shaped oxide film having a width of 40 μm and a length of 500 μm is removed). In the n-type semiconductor distributed Bragg reflector of FIG. 15, no intermediate layer (composition gradient layer) is provided at each interface of AlAs / GaAs, and the composition changes sharply at each interface. In FIG. 14, a large difference is observed in the current-voltage characteristics between the CW measurement and the pulse measurement. It can be seen that the applied voltage is high and the element resistance is large especially in the pulse measurement. Further, also in the case of the CW measurement, a negative resistance appears near the current value of 500 mA, and it can be seen that the depletion and accumulation of carriers at the hetero interface have an effect. As described above, in the n-type distributed Bragg reflector having a steep heterointerface, nonlinearity (negative resistance) of heterocurrent-voltage characteristics, which is considered to be caused by carrier tunneling in the heterobarrier, occurs. Due to the difference in the measurement conditions, the current-voltage characteristics change.
[0033]
On the other hand, FIG. 16 is a diagram showing current-voltage characteristics when a linear composition gradient layer is provided as an intermediate layer at each interface of AlAs / GaAs of an n-type semiconductor distributed Bragg reflector in an element having the same structure as in FIG. It is. FIG. 16 shows two cases where the thickness of the linear composition gradient layer is 20 nm and 30 nm. In FIG. 16, the difference between the pulse measurement and the CW measurement is reduced as compared with FIG. 14, and both are improved to linear characteristics. That is, the difference between the current-voltage characteristics with respect to the measurement conditions (driving conditions) is greatly improved, and the nonlinearity (negative resistance) observed during the CW measurement is also significantly improved. As described above, the influence of the hetero interface on the current-voltage characteristics is significantly reduced, and accordingly, the capacitance caused by depletion of the interface is also significantly reduced.
[0034]
In a surface emitting semiconductor laser device, the device resistance and the capacitance determine the upper limit of the modulation speed of the device due to the miniaturization of the device size and the diameter of the oxidized constriction. Therefore, in order to perform high-speed modulation exceeding 10 Gbps, it is very important to reduce the element resistance and the capacitance as much as possible. In addition to the oxide confinement layer, the capacitance due to the interface of the semiconductor distributed Bragg reflector is reduced. It is important to reduce. In addition, it is not practically preferable that the current-voltage characteristics change or the current-voltage characteristics are non-linear depending on the measurement conditions of the element as shown in FIG.
[0035]
As in the first embodiment, an intermediate layer having a refractive index (forbidden band width) between the semiconductor layers constituting the n-type semiconductor distributed Bragg reflector (semiconductor layer (linear composition gradient in this example) When the layer ()) is provided, as shown in FIG. 16, the occurrence of potential distribution such as spikes and notches can be reduced. In this manner, by smoothing the potential barrier at the hetero interface, it becomes possible to drastically reduce the accumulation and depletion of carriers that have conventionally occurred at the hetero interface. Therefore, the electric resistance can of course be further reduced, but the effect of the hetero interface is more effectively reduced, the non-linearity of the current-voltage characteristic of the n-type distributed Bragg reflector, and the current-voltage characteristic due to the driving conditions are reduced. Changes can be reduced. Furthermore, by suppressing the depletion of carriers at the hetero interface, the capacitance due to the depletion region can be significantly reduced. As described above, the current-voltage characteristics of the n-type semiconductor distributed Bragg reflector are improved, and the capacitance is reduced, so that, for example, a surface emitting semiconductor laser device using this Is easily driven, and higher-speed modulation can be performed.
[0036]
That is, in the first embodiment, in order to reduce the influence of the capacitance due to the n-type semiconductor distributed Bragg reflector, between the two types of semiconductor layers having different refractive indexes constituting the n-type semiconductor distributed Bragg reflector, By providing an intermediate layer (semiconductor layer) having a refractive index between them and smoothing the potential barrier at the hetero interface, a change in current-voltage characteristics due to a difference in driving (measurement) conditions, and a change in current-voltage characteristics Can be reduced, and the capacitance can be reduced by depletion of carriers.
[0037]
Second embodiment
According to a second embodiment of the present invention, in the distributed Bragg reflector of the first embodiment, the intermediate layer has a thickness greater than 20 [nm].
[0038]
In the second embodiment, by setting the thickness of the intermediate layer to the above-described thickness and smoothing the potential barrier at the hetero interface, the nonlinearity in the current-voltage characteristic, the change in the current-voltage characteristic due to the measurement conditions, and An n-type distributed Bragg reflector with reduced electric capacitance due to the heterointerface and excellent in electric characteristics can be obtained.
[0039]
Referring again to FIG. 16, in FIG. 16, the structure provided with the composition gradient layer (intermediate layer) having a thickness of 20 m has a large difference between the CW measurement and the pulse measurement as compared with the structure without the intermediate layer shown in FIG. 14. It can be seen that it has been reduced to That is, the difference in the current-voltage characteristics between the pulse measurement and the CW measurement is significantly reduced by the composition gradient layer having a thickness of 20 nm, and the nonlinearity in the current-voltage characteristics observed in the CW measurement is eliminated. . These results indicate that the potential barrier at the heterointerface of the Bragg reflector can be greatly smoothed in the composition gradient layer having a thickness of 20 nm. Along with this, the capacitance due to the depletion of carriers at the hetero interface can be significantly reduced.
[0040]
In the second embodiment, by providing a composition gradient layer thicker than 20 nm as described above, the influence of the hetero interface is greatly reduced, the current-voltage characteristics of the n-type distributed Bragg reflector are improved, and the hetero interface is improved. Can be reduced.
[0041]
Third embodiment
According to a third embodiment of the present invention, in the n-type distributed Bragg reflector of the first embodiment, the thickness of the intermediate layer is in a range of 30 nm or more.
[0042]
In the third embodiment, by setting the thickness of the intermediate layer to the above-described thickness, the influence of the heterointerface and the capacitance at the heterointerface are reduced, and the n-type distributed Bragg reflector having excellent electric characteristics is provided. Can be obtained.
[0043]
The reason that the influence of the hetero interface is reduced by the intermediate layer is that the hetero layer is flattened by the intermediate layer, and the accumulation and depletion of carriers at the interface are suppressed. . Here, looking again at the current-voltage characteristics of FIG. 16, FIG. 16 shows that two kinds of samples having different composition gradient layers (intermediate layers) due to the effect of smoothing the potential barrier at the hetero interface by the intermediate layer. In both cases, the difference between the current-voltage characteristics in the pulse measurement and the CW measurement, and the nonlinearity in the CW measurement are reduced. It is improved and the difference between CW measurement and pulse measurement is almost eliminated. Therefore, by setting the thickness of the intermediate layer to 30 nm or more, a greater improvement effect can be obtained.
[0044]
In the third embodiment, as described above, by providing a composition gradient layer having a thickness of 30 nm or more, the influence of the hetero interface is more effectively reduced, and the current-voltage characteristics of the n-type distributed Bragg reflector are improved. Is improved, and the capacitance at the hetero interface can be reduced more effectively.
[0045]
Fourth embodiment
According to a fourth embodiment of the present invention, in the n-type distributed Bragg reflector of the first embodiment, the thickness t [nm] of the intermediate layer is different from the reflection wavelength λ [μm] of the distributed Bragg reflector. , 20 <t ≦ (50λ−15) [nm].
[0046]
In the fourth embodiment, with the above-described configuration, it is possible to obtain an n-type distributed Bragg reflector excellent in electric characteristics in which the influence of the heterointerface is reduced while maintaining high reflectance. The distributed Bragg reflector can obtain a higher reflectance as the difference in refractive index between the semiconductor layers constituting the reflector and as the interface becomes steeper. Accordingly, the reflectivity tends to gradually decrease as the thickness of the composition gradient layer increases.
[0047]
FIG. 17 shows this state. That is, FIG. 17 is a diagram showing the differential coefficient of the change in reflectance with respect to the thickness of the composition gradient layer of the distributed Bragg reflector made of AlAs / GaAs in each wavelength band. The number of stacked distributed Bragg reflectors is the number of layers whose reflectance exceeds 99.9% for the first time in each wavelength band. From FIG. 17, it can be seen that the reflectivity starts to change (decrease) slowly and changes rapidly from a certain value. FIG. 17 shows a tangent line to the thickness at which the derivative starts to change in some wavelength bands in order to make this situation easy to understand. From this tangent, it can be seen that a sharp change occurs in any wavelength band from around the differential coefficient exceeding 0.01. As described above, the thickness at which the differential coefficient becomes 0.01 is the thickness (threshold thickness) at which the reflectance change of the distributed Bragg reflector starts to increase rapidly, and the thickness of the composition gradient layer is larger than this threshold thickness. Is too thick, the reflectivity of the distributed Bragg reflector drops sharply. In each wavelength band, the thickness of the composition gradient layer when the derivative is 0.01 (at the threshold thickness) is read as shown in the following table (Table 1), and the reflection wavelength λ of the Bragg reflector [ μm] and the threshold thickness have a linear relationship as shown in the following equation (Equation 1).
[0048]
[Table 1]

[0049]
(Equation 1)
Threshold thickness = (50λ−15) [nm]
[0050]
Here, the reflection wavelength is a wavelength at which the reflectance is highest in the reflection band of the distributed Bragg reflector. Further, in the structure without the intermediate layer, the thickness of the layer constituting the Bragg reflector whose refractive index is represented by n is represented by λ / 4n with respect to the reflection wavelength λ.
[0051]
On the other hand, as described above, the difference in current-voltage characteristics due to driving conditions, and the effect of improving non-linearity and accumulation and depletion of carriers at the heterointerface are remarkable when the thickness of the intermediate layer is large. It is desirable to provide a thick intermediate layer. However, if the thickness is too large, the above-described problem occurs, so the thickness of the intermediate layer has an optimum range.
[0052]
From the above results, when considering both the electrical characteristics (current-voltage characteristics) and the optical characteristics (reflectance), the optimum range of the thickness of the intermediate layer is determined by the reflection wavelength λ [μm of the distributed Bragg reflector. ] Can be expressed as 20 <t ≦ (50λ−15) [nm]. Here, the inequality defining the range of the intermediate layer thickness t is satisfied in the range of λ> 0.7 μm, and can be applied to an n-type distributed Bragg reflector having a reflection wavelength longer than this wavelength. For example, an element using an AlGaAs-based material as an active layer material can typically obtain laser oscillation in the 0.78 μm to 0.85 μm band. When a GaInAs-based material is used, laser oscillation can be obtained in the 0.98 μm band to 1.2 μm band. Furthermore, by using a GaInNAsSbP-based material, laser oscillation can be obtained at a longer wavelength than the 1.2 μm band.
[0053]
Therefore, an n-type distributed Bragg reflector having an intermediate layer having a thickness in the range defined by the fourth embodiment can be formed by using a laser made of these materials for light having a wavelength longer than 0.7 μm. And optical devices such as optical modulators.
[0054]
Fifth embodiment
The fifth embodiment of the present invention is a surface emitting semiconductor laser device using the n-type semiconductor distributed Bragg reflector according to any of the first to fourth embodiments.
[0055]
In the surface emitting semiconductor laser device according to the fifth embodiment, the capacitance of the surface emitting semiconductor laser device is reduced by using the n-type semiconductor distributed Bragg reflector according to any one of the first to fourth embodiments. Thus, high-speed modulation becomes possible.
[0056]
That is, the surface emitting semiconductor laser device of the fifth embodiment uses the n-type semiconductor distributed Bragg reflector of any one of the first to fourth embodiments. The potential distribution of spikes, notches, etc., formed in the pattern is smoothed. Therefore, the influence of the depletion and accumulation of carriers due to this is drastically reduced as compared with the conventional surface emitting semiconductor laser device, and the electric resistance as well as the capacitance at the hetero interface are reduced.
[0057]
Therefore, the surface emitting semiconductor laser device of the fifth embodiment has a structure more suitable for high-speed modulation than the conventional surface emitting semiconductor laser device, and the capacitance of the n-type semiconductor distributed Bragg reflector is reduced. And high-speed modulation exceeding 10 Gbps can be easily performed.
[0058]
Sixth embodiment
According to a sixth embodiment of the present invention, in a surface emitting semiconductor laser device provided with an n-type semiconductor distributed Bragg reflector and a p-type semiconductor distributed Bragg reflector with an active layer interposed, the n-type semiconductor distributed Bragg reflector is provided. The container is processed into a mesa shape.
[0059]
In the sixth embodiment, in a surface emitting semiconductor laser device provided with an n-type semiconductor distributed Bragg reflector and a p-type semiconductor distributed Bragg reflector with an active layer interposed, the n-type semiconductor distributed Bragg reflector is By being processed into the mesa shape, the path of the current injected into the element portion (resonance region) through the n-type semiconductor distributed Bragg reflector is limited, and the area of the n-type semiconductor distributed Bragg reflector that contributes to the capacitance is limited. , Thereby reducing the capacitance and enabling high-speed modulation.
[0060]
That is, in the sixth embodiment, in the surface emitting semiconductor laser device provided with the n-type distributed Bragg reflector and the p-type distributed Bragg reflector with the active layer interposed therebetween, the n-type distributed Bragg reflector Is processed into a mesa shape (more specifically, as shown in the example of FIG. 4 described later, a region other than the element portion (resonance region) of the n-type semiconductor distributed Bragg reflector is removed by etching to the substrate surface. ing). As described above, a potential distribution such as a spike or a notch is formed at a hetero interface composed of two types of semiconductor layers having different electron affinities, and a capacitance is generated due to depletion of carriers. Conventionally, in a surface emitting laser element, an oxide confined structure formed by oxidizing a semiconductor layer containing Al such as AlAs is provided in order to reduce a threshold current. Since holes have a shorter diffusion length than electrons and can achieve high confinement efficiency, the constriction structure is provided on the p-type semiconductor distributed Bragg reflector side. On the side of the n-type semiconductor distributed Bragg reflector, a constriction structure is not particularly provided, and the structure is such that electrons as majority carriers are injected from electrodes formed on the entire back surface of the substrate. Therefore, in the conventional surface emitting semiconductor laser device, electrons have a current path wider than the mesa diameter, which is a path of holes, and the area through which the electron current passes in the n-type semiconductor distributed Bragg reflector is p-type. Wider than semiconductor distributed Bragg reflectors. Since the capacitance increases in proportion to the area, the capacitance due to the n-type semiconductor distributed Bragg reflector increases in response to the spread of the current, which causes the element capacitance to increase. .
[0061]
In the sixth embodiment, specifically, a region other than the element portion (resonance region) of the n-type semiconductor distributed Bragg reflector is removed by etching, so that a current path of electrons is formed in a region left by the etching removal. This limits the capacitance due to the n-type semiconductor distributed Bragg reflector. Therefore, the surface emitting semiconductor laser device according to the sixth embodiment has a structure more suitable for high-speed modulation than the conventional surface emitting semiconductor laser device. In the surface emitting semiconductor laser device according to the sixth embodiment, n Since the capacitance of the distributed semiconductor Bragg reflector is reduced, high-speed modulation of 10 Gbps or more can be easily performed.
[0062]
In other words, in the surface emitting semiconductor laser device according to the sixth embodiment, the current path in the n-type semiconductor distributed Bragg reflector is narrowed to approximately the same as the mesa diameter of the element portion (resonance region), so that the capacitance is reduced. The area of the n-type semiconductor distributed Bragg reflector that contributes to the above can be reduced, the capacitance of the element can be reduced, and high-speed modulation can be performed.
[0063]
Seventh embodiment
According to a seventh embodiment of the present invention, in a surface emitting semiconductor laser device provided with an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed, the n-type distributed Bragg reflector is provided. Is characterized in that a region other than the resonance region is increased in resistance.
[0064]
According to the seventh embodiment, in a surface emitting semiconductor laser device provided with an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed therebetween, the resonance of the n-type distributed Bragg reflector is achieved. Since the region other than the region has a high resistance, the path of the current injected into the element portion (resonance region) through the n-type semiconductor distributed Bragg reflector is limited, and the n-type semiconductor distributed Bragg that contributes to the capacitance is limited. The area of the reflector is reduced, whereby the capacitance can be reduced and high speed modulation is possible.
[0065]
That is, in the seventh embodiment, the region other than the element portion (resonant region) of the n-type semiconductor distributed Bragg reflector is made to have a high resistance, and is injected from the substrate side as in the description of the sixth embodiment. Since the current path of electrons is limited to a part of the mesa region of the n-type semiconductor distributed Bragg reflector, the area of the n-type semiconductor distributed Bragg reflector which contributes as a capacitance is reduced, whereby the surface emitting semiconductor The capacitance of the laser device can be made smaller than that of a conventional surface emitting semiconductor laser device, and a structure suitable for high-speed modulation can be obtained.
[0066]
In other words, in the surface emitting semiconductor laser device of the seventh embodiment, similarly to the sixth embodiment, the current path in the n-type semiconductor distributed Bragg reflector is substantially equal to the mesa diameter of the element portion (resonance region). , The area of the n-type semiconductor distributed Bragg reflector that contributes as capacitance can be reduced, the capacitance of the element can be reduced, and high-speed modulation can be performed.
[0067]
As a method for increasing the resistance of the n-type semiconductor distributed Bragg reflector, for example, a method such as hydrogen ion implantation can be used as in Example 5 described later. In particular, the use of hydrogen ion implantation has advantages such as excellent heat dissipation, easy embedding, and excellent physical strength because the distance between the active region and the etched surface is short. In particular, high output can be obtained due to excellent heat radiation. In fact, in the surface emitting semiconductor laser device of the seventh embodiment, high-speed modulation of 10 Gbps or more can be easily performed by reducing the capacitance of the n-type distributed Bragg reflector.
[0068]
Eighth embodiment
In an eighth embodiment of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh embodiment, the n-type semiconductor distributed Bragg reflector is provided between two kinds of semiconductor layers having different refractive indexes. An intermediate layer (semiconductor layer) having a refractive index between two types of semiconductor layers is provided.
[0069]
In the eighth embodiment, in the surface emitting semiconductor laser device according to the sixth or seventh embodiment, the n-type semiconductor distributed Bragg reflector is provided between the two types of semiconductor layers having different refractive indexes. Since the intermediate layer (semiconductor layer) having a refractive index between the semiconductor layers is provided, the capacitance at the hetero interface of the n-type distributed Bragg reflector can be further reduced. Further high-speed modulation becomes possible.
[0070]
That is, in the eighth embodiment, in the surface emitting semiconductor laser device according to the sixth or seventh embodiment, two types of semiconductor layers are provided at a hetero interface of two types of semiconductor layers constituting the n-type semiconductor distributed Bragg reflector. An intermediate layer (semiconductor layer) having a refractive index (forbidden band width) between them. As described in any of the first to fifth embodiments, by providing the intermediate layer (semiconductor layer) at the hetero interface between the two types of semiconductor layers, the potential at the hetero interface is smoothed and the depletion of carriers is caused. , The accumulation is reduced, and the capacitance caused by the depletion can be drastically reduced. Further, as in the sixth or seventh embodiment, the area of the semiconductor distributed Bragg reflector that effectively contributes as a capacitance is reduced by limiting the electron path of the n-type semiconductor distributed Bragg reflector to the mesa region. Can be reduced. Therefore, as in the eighth embodiment, by using these together, the capacitance of the surface emitting semiconductor laser element can be reduced more effectively, and a structure suitable for very high-speed modulation can be obtained. Can be. In fact, the surface emitting semiconductor laser device according to the eighth embodiment can easily perform high-speed modulation of 10 Gbps or more because the capacitance of the n-type semiconductor distributed Bragg reflector is reduced as described above. .
[0071]
Ninth embodiment
According to a ninth embodiment of the present invention, in the surface emitting semiconductor laser device of the sixth or seventh embodiment, the n-type semiconductor distributed Bragg reflector is provided between two kinds of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness of the intermediate layer is greater than 20 [nm].
[0072]
With the configuration of the ninth embodiment, the path of the electron current can be limited, the area of the n-type semiconductor distributed Bragg reflector that contributes to the capacitance can be reduced, and the heterostructure of the n-type semiconductor distributed Bragg reflector can be reduced. The capacitance at the interface is reduced, and high-speed modulation becomes possible.
[0073]
Tenth embodiment
A tenth embodiment of the present invention is the surface emitting semiconductor laser device according to the sixth or seventh embodiment, wherein the n-type semiconductor distributed Bragg reflector is provided between two kinds of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness of the intermediate layer is in a range of 30 [nm] or more.
[0074]
With the configuration of the tenth embodiment, the path of the electron current can be limited, the area of the n-type semiconductor distributed Bragg reflector that contributes to the capacitance can be reduced, and the heterostructure of the n-type semiconductor distributed Bragg reflector can be reduced. The capacitance at the interface is reduced, and high-speed modulation becomes possible.
[0075]
Eleventh embodiment
An eleventh embodiment of the present invention is the surface emitting semiconductor laser device according to the sixth or seventh embodiment, wherein the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness t [nm] of the intermediate layer is 20 <t ≦ ([lambda]) with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector. 50 [lambda] -15) [nm].
[0076]
With the configuration of the eleventh embodiment, the path of the electron current can be limited, and the area of the n-type semiconductor distributed Bragg reflector that contributes to the capacitance can be reduced. The capacitance at the interface is reduced, and high-speed modulation becomes possible.
[0077]
Twelfth embodiment
According to a twelfth embodiment of the present invention, in the surface emitting semiconductor laser device of any one of the fifth to eleventh embodiments, the active layer is made of a group III material and a group V material. It is characterized in that the group III material is any or all of Ga and In, and the group V material of the active layer is any or all of As, N, Sb, and P.
[0078]
According to the twelfth embodiment, in the surface emitting semiconductor laser device according to any one of the fifth to eleventh embodiments, the active layer is made of a group III material and a group V material. Since the material is any or all of Ga and In and the V group material of the active layer is any or all of As, N, Sb, and P, an optical fiber is formed on the GaAs substrate. A surface emitting semiconductor laser device that oscillates at a longer wavelength than 1.1 μm, including the 1.3 μm band and the 1.5 μm band, which is important for communication, can be obtained. Further, since GaAs can be used as the semiconductor substrate, a high-quality semiconductor distributed Bragg reflector of AlGaAs / GaAs can be used for the resonator mirror. Therefore, a long-wavelength surface emitting semiconductor laser device having a low threshold value and excellent characteristics can be provided.
[0079]
That is, in the twelfth embodiment, the group III material of the active layer is any or all of Ga and In, and the group V material of the active layer is any of As, N, Sb, and P, or The active layer composed of these materials is capable of crystal growth on a GaAs substrate, and has high reflectivity, thermal conductivity, and process control (such as crystal growth and Al (Ga) As mixed crystal, etc.). A surface emitting semiconductor laser device using a DBR made of an AlGaAs-based material having excellent characteristics in terms of (selective oxidation) can be obtained. Also, by using these materials for the active layer, oscillation of a longer wavelength than 1.1 μm including the 0.85 μm band, the 0.98 μm band, and the 1.3 μm band and the 1.5 μm band which are important in optical fiber communication is achieved. Obtainable.
[0080]
Thus, for example, by combining a laser element having a wavelength band of 1.3 μm with a quartz single mode laser, high-speed optical communication becomes possible. In addition, large-capacity communication can be performed by using DWDM using elements in the 1.5 μm band.
[0081]
At this time, among the above-mentioned materials (active layer materials), the GaInN (Sb) As mixed crystal material can obtain an oscillation of 1.1 μm or more and, in addition, can obtain a GaAs layer serving as a carrier confinement layer. Since the band discontinuity of the conduction band of the GaInN (Sb) As layer is large and the overflow of electrons can be reduced, stable oscillation can be obtained up to a high temperature. In addition to these, in the surface emitting semiconductor laser device of the present invention, since the capacitance of the n-type semiconductor distributed Bragg reflector is reduced, high-speed modulation can be easily performed as compared with the conventional device. Therefore, according to the present invention, a surface emitting semiconductor laser device suitable for optical communication and optical transmission can be provided.
[0082]
Thirteenth embodiment
The thirteenth embodiment of the present invention is a surface emitting laser array constituted by the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments.
[0083]
Since the surface emitting laser array according to the thirteenth embodiment includes the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, the capacitance of the device is smaller than that of the conventional device, and high-speed modulation is performed. Becomes possible.
[0084]
That is, the surface emitting semiconductor laser device constituting the surface emitting laser array of the thirteenth embodiment can perform high-speed modulation by reducing the capacitance by the n-type semiconductor distributed Bragg reflector. The surface-emitting laser array constituted by these surface-emitting semiconductor laser elements can also perform high-speed modulation. Further, by forming the surface emitting laser array, parallel optical transmission is facilitated, and higher speed, large capacity optical transmission and optical communication can be performed. Thus, in the thirteenth embodiment, it is possible to provide a surface emitting laser array capable of high-speed, large-capacity optical transmission and optical communication.
[0085]
Fourteenth embodiment
The fourteenth embodiment of the present invention is a surface-emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, or a surface-emitting laser module constituted by the surface-emitting laser array according to the thirteenth embodiment. .
[0086]
Since the surface emitting laser module according to the fourteenth embodiment includes the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments or the surface emitting laser array according to the thirteenth embodiment, High speed, large capacity optical transmission and optical communication become possible.
[0087]
That is, the surface emitting laser module of the fourteenth embodiment includes a surface emitting semiconductor laser element or a surface emitting laser array in which the capacitance of the n-type semiconductor distributed Bragg reflector is reduced and which can perform higher-speed modulation than before. Since it is used, high-speed, large-capacity optical transmission and optical communication become possible. Specifically, as in Example 7 described later, a surface emitting laser module combining a 1.3 μm band surface emitting semiconductor laser device using a GaInNAs mixed crystal semiconductor as an active layer material and a quartz single mode fiber is 1.3 μm. Since the band corresponds to the zero-dispersion band of quartz, the structure is very suitable for high-speed modulation. By using this surface emitting laser module, high-speed, large-capacity optical communication and optical transmission can be performed. Thus, in the fourteenth embodiment, it is possible to provide a surface emitting laser module capable of high-speed, large-capacity optical transmission and optical communication.
[0088]
15th embodiment
The fifteenth embodiment of the present invention is directed to the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, the surface emitting laser array according to the thirteenth embodiment, or the surface emitting device according to the fourteenth embodiment. It is an optical interconnection system constituted by a light emitting laser module.
[0089]
The optical interconnection system according to the fifteenth embodiment includes the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, the surface emitting laser array according to the thirteenth embodiment, or the fourteenth embodiment. Since it is constituted by the surface emitting laser module of the embodiment, high-speed and large-capacity optical transmission is possible.
[0090]
That is, the optical interconnection system according to the fifteenth embodiment has a surface emitting semiconductor laser element or a surface emitting laser array in which the capacitance of the n-type semiconductor distributed Bragg reflector is reduced and which can perform high-speed modulation as compared with the related art. Alternatively, since a surface emitting laser module is used, high-speed, large-capacity optical transmission and optical communication can be performed. Specifically, as in Example 7 described later, an optical interconnection constituted by a surface emitting laser module combining a 1.3 μm band surface emitting laser using a GaInNAs mixed crystal semiconductor as an active layer material and a quartz single mode fiber. Since the 1.3 μm band corresponds to the zero-dispersion band of quartz in the system, the configuration is very suitable for high-speed modulation, and high-speed, large-capacity optical communication and optical transmission can be performed. In addition, a surface emitting semiconductor laser device using a GaInNAs mixed crystal semiconductor as an active layer can obtain stable oscillation up to a high temperature with respect to a change in the operating environment temperature of the device. And an optical interconnection system with a high level of reliability can be obtained. Thus, in the fifteenth embodiment, high-speed, large-capacity optical communication is possible, and a more reliable optical interconnection system can be provided.
[0091]
Sixteenth embodiment
The sixteenth embodiment of the present invention is directed to the surface-emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, the surface-emitting laser array according to the thirteenth embodiment, or the surface according to the fourteenth embodiment. It is an optical communication system constituted by a light emitting laser module.
[0092]
The optical communication system according to the sixteenth embodiment is the surface emitting semiconductor laser device according to any one of the fifth to twelfth embodiments, the surface emitting laser array according to the thirteenth embodiment, or the fourteenth embodiment. , High-speed, large-capacity optical communication becomes possible.
[0093]
That is, in the optical communication system according to the sixteenth embodiment, the surface emitting semiconductor laser device or the surface emitting laser array or the surface emitting laser device in which the capacitance of the n-type semiconductor distributed Bragg reflector is reduced and which can perform high-speed modulation as compared with the related art. Since the light emitting laser module is used, high-speed, large-capacity optical transmission and optical communication can be performed. Specifically, as in Example 7 to be described later, an optical communication system including a surface emitting laser module in which a 1.3 μm band surface emitting laser using a GaInNAs mixed crystal semiconductor as an active layer material and a quartz single mode fiber are combined. Since the 1.3 μm band corresponds to the zero-dispersion band of quartz, the configuration is very suitable for high-speed modulation, and high-speed, large-capacity optical transmission can be performed. In addition, a surface emitting semiconductor laser device using a GaInNAs mixed crystal semiconductor as an active layer can obtain stable oscillation up to a high temperature with respect to a change in the operating environment temperature of the device. And an optical communication system having a high degree of reliability can be obtained. Thus, in the sixteenth embodiment, high-speed, large-capacity optical transmission is possible, and a more reliable optical communication system can be provided.
[0094]
【Example】
Next, examples of the present invention will be described.
[0095]
(Example 1)
FIG. 1 is a diagram for explaining an example of an n-type semiconductor distributed Bragg reflector according to the first embodiment as a first embodiment. The n-type semiconductor distributed Bragg reflector of FIG. 1 is a semiconductor distributed Bragg reflector having a design reflection wavelength of 0.98 μm, and includes an n-AlAs layer, an n-GaAs layer, an n-AlAs layer, and an n-GaAs layer. And an n-AlGaAs linear composition gradient layer (intermediate layer) having a thickness of 30 nm in which the Al composition is linearly changed from one value to the other value as shown in FIG. It is constituted by.
[0096]
Here, the thickness of the n-AlAs layer of the n-type semiconductor distributed Bragg reflector of FIG. 1 is 51.6 nm, and the thickness of the n-GaAs layer is 40.9 nm. For light having a wavelength of 0.98 μm, the thickness at which the phase change of light in each semiconductor layer becomes π / 2, that is, the thickness satisfying the multiple reflection phase condition in the semiconductor distributed Bragg reflector is 82.9 nm. , 69.5 nm, and considering the phase change in the linear composition gradient layer having a thickness of 30 nm, the thicknesses of the n-AlAs layer and the n-GaAs layer are set to the above thicknesses.
[0097]
The n-type semiconductor distributed Bragg reflector of FIG. 1 includes trimethylaluminum (TMA), trimethylgallium (TMG), arsine (AsH).₃2.) Crystal growth can be performed by MOCVD using gas as a raw material. In addition, hydrogen selenide (H₂Se) can be used. In the MOVCD method, since the composition of AlGaAs can be controlled by changing the supply amount of the raw material, the composition gradient layer can be easily grown.
[0098]
In the n-type semiconductor distributed Bragg reflector shown in FIG. 1, the provision of the composition gradient layer (intermediate layer) at each hetero interface makes it possible to reduce not only the electric resistance but also the capacitance at the hetero interface as compared with the conventional one. did it.
[0099]
(Example 2)
FIG. 18 is a diagram for explaining an example of the n-type semiconductor distributed Bragg reflector according to the third embodiment as Example 2. The n-type semiconductor distributed Bragg reflector of FIG. 1 is a semiconductor distributed Bragg reflector having a designed reflection wavelength of 1.3 μm, and has an n-Al_0.9Ga_0.1As layer, n-GaAs layer, n-Al_0.9Ga_0.1An n-AlGaAs linear composition gradient layer (intermediate layer) having a thickness of 40 nm in which the Al composition is linearly changed from one value to the other value as shown in FIG. 2 between the As layer and the n-GaAs layer, It is configured by being periodically laminated.
[0100]
Here, the thickness of each layer is selected such that the thickness according to the phase change of the light in the composition gradient layer is reduced and the phase condition of the multiple reflection of the Bragg reflector is satisfied as in the first embodiment. Here, the thickness of the composition gradient layer of 40 nm is selected in the range of 20 <t ≦ (50λ−15) [nm] with respect to the reflection wavelength λ (= 1.3 μm) of the distributed Bragg reflector, and the reflection is high. The capacitance due to the hetero interface was able to be reduced as compared with the related art while maintaining the ratio. Therefore, a suitable n-type distributed Bragg reflector could be obtained as a resonator mirror for a surface emitting laser element or the like.
[0101]
(Example 3)
FIG. 3 is a diagram for explaining an example of the surface emitting semiconductor laser device of the fifth and twelfth embodiments as a third embodiment. The surface emitting semiconductor laser device shown in FIG. 3 is a 1.3 μm band surface emitting semiconductor laser device using GaInNAs as an active layer.₃) Crystal growth is performed by MOCVD using gas as a raw material. At this time, dimethylhydrazine (DMHy) can be used as a nitrogen source for the active layer. Also, CBr is used for the p-type dopant.₄And the n-type dopant is H₂Se can be used.
[0102]
The surface emitting semiconductor laser device of FIG. 3 is manufactured as follows. That is, first, crystal growth of an n-GaAs buffer layer is performed on an n-GaAs substrate, and then crystal growth of 36 pairs of an n-type semiconductor distributed Bragg reflector having a pair of AlAs / GaAs is performed. At this time, as shown in Example 1, the n-AlAs / GaAs semiconductor distributed Bragg reflector has a 30 nm-thick n-type n-type film in which the Al composition is linearly changed from one composition to the other composition as shown in Example 1. An AlGaAs linear composition gradient layer is provided as an intermediate layer (semiconductor layer).
[0103]
After forming the n-AlAs / GaAs semiconductor distributed Bragg reflector in this manner, a GaAs resonator spacer layer, a GaInNAs / GaAs multiple quantum well structure (active layer), a GaAs resonator spacer layer, and an Al_0.8Ga_0.222 pairs of p-type semiconductor distributed Bragg reflectors having As / GaAs as a pair are sequentially formed. Here, an AlAs selective oxidation layer having a thickness of 30 nm is provided at the interface of the first pair of p-type semiconductor distributed Bragg reflectors. Further, at each interface of the p-type semiconductor distributed Bragg reflector, a linear composition gradient layer (thickness: 30 nm) in which the Al composition is linearly changed from one composition to the other composition is provided in order to reduce the element resistance. ing. Further, the doping density in the vicinity of the surface of the GaAs layer serving as the resurface layer of the p-type semiconductor distributed Bragg reflector is 1 × 10¹⁹cm^-3As a contact layer.
[0104]
Here, the thickness of each layer constituting the p-type semiconductor distributed Bragg reflector and the n-type semiconductor distributed Bragg reflector, including the composition gradient layer (intermediate layer), is the same as that of the first embodiment. Al is adjusted to satisfy the reflection phase condition, and the Al_0.8Ga_0.2The thickness of the As layer is adjusted in the same manner. In this surface emitting semiconductor laser device, the phase change of the oscillating light in the active layer and the two resonator spacer layers is equal to 2π, forming a 1λ cavity. Further, the active layer is disposed at the center of the 1λ cavity, that is, at the position that is the antinode of the standing wave of light.
[0105]
Next, each layer from the surface of the p-GaAs contact layer to the middle of the GaAs resonator spacer layer in contact with the n-semiconductor distributed Bragg reflector is mesaed by a known photolithography and dry etching method. Processed (dry etching removed) into shape. At this time, the mesa to be the element portion has a square mesa shape of 30 μm × 30 μm.
[0106]
Next, heating is performed in an atmosphere obtained by bubbling pure water heated to 80 ° C. with a nitrogen gas, from the etching side surface of the AlAs selective oxidation layer to the element central portion, and performing selective oxidation from the lateral direction to perform current confinement. It has a structure. At this time, the size of the region serving as the current path was 5 μm × 5 μm.
[0107]
Next, after the mesa portion is embedded with an insulating resin such as polyimide, an electrode material is deposited and lift-off is performed to form a p-side electrode having an opening in a light emitting portion on the upper surface of the element. Next, an n-side electrode is formed on the back surface of the substrate, and the surface emitting semiconductor laser device of FIG. 3 can be manufactured.
[0108]
In the surface emitting semiconductor laser device of FIG. 3, a composition gradient layer is provided between the heterointerfaces of both the p-type distributed Bragg reflector and the n-type distributed Bragg reflector. The composition gradient layer provided in the p-type semiconductor distributed Bragg reflector is for reducing the element resistance as in the known art. Further, by providing the n-type composition gradient layer in the n-type semiconductor distributed Bragg reflector, the capacitance of the device can be drastically reduced as compared with the conventional device. That is, in the surface emitting semiconductor laser device of FIG. 3, the n-type composition gradient layer is provided on the n-type semiconductor distributed Bragg reflector, so that spikes and notches at the interface between AlAs and GaAs constituting the n-type semiconductor distributed Bragg reflector are provided. Are smoothed. Thereby, accumulation and depletion of carriers are suppressed, the capacitance is drastically reduced, and a structure suitable for high-speed modulation is obtained. Actually, the surface emitting semiconductor laser device of FIG. 3 could easily perform high-speed modulation of 10 Gbps or more.
[0109]
The surface emitting semiconductor laser device of FIG. 3 uses GaInNAs as an active layer material, and oscillates at 1.3 μm using a semiconductor distributed Bragg reflector having excellent characteristics of Al (Ga) As / GaAs on a GaAs substrate. The surface emitting semiconductor laser device can be provided. That is, the GaInNAs mixed crystal has a large conduction band discontinuity with a barrier layer such as GaAs or a resonator spacer layer and has a high effect of confining electrons in the active layer, so that stable oscillation can be obtained up to a high temperature. The 1.3 μm band corresponds to the zero dispersion band of the quartz fiber, and high-speed communication is possible by using the single mode fiber. As described above, the surface emitting semiconductor laser device of FIG. 3 can actually perform high-speed modulation, and can easily perform high-speed communication by combining with the quartz single-mode fiber.
[0110]
(Example 4)
FIG. 4 is a diagram for explaining an example of the surface emitting semiconductor laser device according to the sixth and eighth embodiments as a fourth embodiment. The surface emitting semiconductor laser device of FIG. 4 is a 0.98 μm band surface emitting semiconductor laser device having a GaInAs / GaAs multiple quantum well as an active layer, and is formed on an n-GaAs substrate by MOCVD in the same manner as in Example 3. Growth is being made.
[0111]
That is, in the surface emitting semiconductor laser device of FIG._0.8Ga_0.2After crystal growth of 36 pairs of n-type semiconductor distributed Bragg reflectors having As / GaAs as a pair,_0.15Ga_0.85As resonator spacer layer, GaInAs / GaAs multiple quantum well structure, Al_0.15Ga_0.85As resonator spacer layer, Al_0.8Ga_0.222 pairs of p-type semiconductor distributed Bragg reflectors having As / GaAs as a pair are sequentially formed.
[0112]
Here, in the surface emitting semiconductor laser device of FIG. 4, a linear composition gradient layer having a thickness of 30 nm for reducing the device resistance is provided only in the p-type semiconductor distributed Bragg reflector. Further, an AlAs selective oxidation layer is provided on the p-type semiconductor distributed Bragg reflector as in the third embodiment.
[0113]
The thickness of the layer constituting the semiconductor distributed Bragg reflector is such that the composition gradient layer and the selective oxidation layer are formed so as to satisfy the multiple reflection phase condition of the distributed Bragg reflector with respect to light having an oscillation wavelength of 0.98 μm. The thickness is set in consideration of the thickness.
[0114]
By the way, the surface emitting semiconductor laser device of Example 4 has the n-type semiconductor distributed Bragg reflector etched (dry-etched) to the substrate surface (that is, the n-type semiconductor distributed Bragg reflector is etched into a mesa shape). Due to the processing, the electron path in the n-type semiconductor distributed Bragg reflector is limited to the mesa region.
[0115]
Originally, in this surface-emitting semiconductor laser device, dry etching is a step performed to oxidize the selective oxidation layer in the lateral direction. In the conventional surface-emitting semiconductor laser device, in the middle of the cavity spacer layer, or , About 2 to 3 pairs of n-type semiconductor distributed Bragg reflectors are partially removed by etching. Therefore, in the conventional surface emitting semiconductor laser device, the n-type semiconductor distributed Bragg reflector does not have a constriction structure for electrons, and the electron current flows from the n-side electrode provided on the entire back surface of the substrate to the mesa diameter. The active region is implanted through a wider region of the n-type semiconductor distributed Bragg reflector. At this time, the capacitance at the interface of the n-type semiconductor distributed Bragg reflector in the region serving as an electron current path contributes as the capacitance of the surface emitting semiconductor laser device.
[0116]
Therefore, as in the fourth embodiment, the capacitance can be reduced by etching the n-type semiconductor distributed Bragg reflector to the same extent as the mesa diameter by etching (by processing into a mesa shape). . That is, the capacitance of the surface emitting semiconductor laser device of Example 4 is smaller than that of the conventional device, and is suitable for high-speed modulation. In fact, the surface emitting semiconductor laser device of Example 4 could easily perform high-speed modulation exceeding 10 Gbps.
[0117]
Further, by using the n-type semiconductor distributed Bragg reflector having the configuration of FIG. 5 for the n-type semiconductor distributed Bragg reflector of the surface-emitting semiconductor laser device of FIG. 4, the capacitance of the surface-emitting semiconductor laser device can be further reduced. Becomes possible. That is, the n-type semiconductor distributed Bragg reflector of FIG. 5 is similar to the n-type semiconductor distributed Bragg reflector of FIG._0.8Ga_0.2An n-AlGaAs linear composition gradient layer (intermediate layer) in which the Al composition is changed linearly from one to the other is provided at the hetero interface between the As layer and the n-GaAs layer, and the n-type semiconductor shown in FIG. By using the distributed Bragg reflector as the n-type semiconductor distributed Bragg reflector of the surface emitting semiconductor laser device shown in FIG. 4, the capacitance due to the hetero interface can be drastically reduced, and the path of the electron current is narrowed to reduce the electrostatic capacitance. It is possible to reduce the area of the region that contributes as the capacitance, and thus it is possible to further reduce the element capacitance. Therefore, in the surface emitting semiconductor laser device of FIG. 4, by using the n-type distributed Bragg reflector of FIG. 5 as the n-type distributed Bragg reflector, an element structure suitable for very high-speed modulation can be obtained. In such a surface emitting semiconductor laser device, high-speed modulation of 10 Gbps or more could be easily performed.
[0118]
(Example 5)
FIG. 6 is a view for explaining an example of the surface emitting semiconductor laser device according to the seventh and eighth embodiments as Example 5. The surface emitting semiconductor laser device of FIG. 6 is a 0.98 μm band surface emitting semiconductor laser device having a GaInAs / GaAs multiple quantum well as an active layer, and crystal growth on an n-GaAs substrate by MOCVD in the same manner as in Example 3. Has been made.
[0119]
That is, in the surface emitting semiconductor laser device shown in FIG. 6, 36 pairs of n-type semiconductor distributed Bragg reflectors each having a pair of AlAs / GaAs are crystal-grown,_0.15Ga_0.85As resonator spacer layer, GaInAs / GaAs multiple quantum well structure, Al_0.15Ga_0.85As resonator spacer layer, Al_0.8Ga_0.222 pairs of p-type semiconductor distributed Bragg reflectors having As / GaAs as a pair are sequentially formed.
[0120]
Here, in the surface emitting semiconductor laser device of FIG. 6, a linear composition gradient layer having a thickness of 30 nm for reducing the device resistance is provided only in the p-type semiconductor distributed Bragg reflector. The p-type semiconductor distributed Bragg reflector is provided with an AlAs selective oxidation layer as in the third embodiment.
[0121]
The thickness of the layer constituting the semiconductor distributed Bragg reflector is such that the composition gradient layer and the selective oxidation layer are formed so as to satisfy the multiple reflection phase condition of the distributed Bragg reflector with respect to light having an oscillation wavelength of 0.98 μm. The thickness is set in consideration of the thickness.
[0122]
By the way, in the surface emitting semiconductor laser device of the fifth embodiment, each layer from the surface of the p-GaAs contact layer to the middle of the GaAs resonator spacer layer in contact with the n-semiconductor distributed Bragg reflector has a mesa shape as in the third embodiment. (Dry etching removal), hydrogen ions are implanted into the n-type semiconductor distributed Bragg reflector using the resist pattern used for the dry etching as a mask, and the entire region of the implanted n-type semiconductor distributed Bragg reflector is removed. The resistance has been increased. That is, the resistance of the p-type semiconductor distributed Bragg reflector other than the mesa portion (other than the resonance region) is increased. After such ion implantation, an oxidized constriction structure is provided by selective oxidation of the AlAs layer, as in the third embodiment, and then buried with an insulating resin, and a p-side electrode and an n-side electrode are formed.
[0123]
As described in the fourth embodiment, in the conventional surface emitting semiconductor laser device, the n-type semiconductor distributed Bragg reflector does not have a constriction structure for electrons, and the current path of the electrons is n-type semiconductor. At the distributed Bragg reflector, it spreads over a region wider than the mesa diameter, and the capacitance of the heterointerface in the region of the n-type semiconductor distributed Bragg reflector contributes as the capacitance of the surface emitting semiconductor laser device.
[0124]
On the other hand, as in the surface emitting semiconductor laser device of the fifth embodiment, unnecessary resistance is provided by providing a high-resistance region in the n-type semiconductor distributed Bragg reflector by hydrogen ion implantation and narrowing the electron current path. The electric capacity can be reduced. Therefore, the surface emitting semiconductor laser device of the fifth embodiment has a structure suitable for high-speed modulation. Further, since the constriction structure of the electron current in the n-type semiconductor distributed Bragg reflector is formed by increasing the resistance by hydrogen ion implantation, the mesa height does not need to be increased unnecessarily, and the physical strength of the element is also improved. It is expensive and easy to embed with an insulating resin. Further, in the surface emitting semiconductor laser device of Example 5, since the distance between the active region and the etched surface is short, heat radiation to the substrate side does not need to be reduced, and the effect of the decrease in output due to heat is small. In fact, in the surface emitting semiconductor laser device of Example 5, high-speed modulation exceeding 10 Gbps could be easily realized because the capacitance of the n-type semiconductor distributed Bragg reflector could be reduced.
[0125]
Further, by using the n-type semiconductor distributed Bragg reflector having the configuration of FIG. 7 for the n-type semiconductor distributed Bragg reflector of the surface-emitting semiconductor laser device of FIG. 6, the capacity of the surface-emitting semiconductor laser device can be further reduced. Becomes possible. That is, similarly to the n-type distributed Bragg reflector of FIG. 1, the n-type semiconductor distributed Bragg reflector of FIG. 7 has an Al composition from one side to the other at the hetero interface between the n-AlAs layer and the n-GaAs layer. An n-AlGaAs linear composition gradient layer (intermediate layer) which is changed linearly is provided, and the n-type semiconductor distributed Bragg reflector of FIG. 7 is replaced with the n-type semiconductor distributed Bragg reflection of the surface emitting semiconductor laser device of FIG. By using it as a device, the capacitance due to the hetero interface can be drastically reduced, and at the same time, the area of the region where the electron current path is narrowed and contributes to the capacitance can be reduced. Can be reduced. Therefore, in the surface emitting semiconductor laser device of FIG. 6, by using the n-type distributed Bragg reflector of FIG. 7 as the n-type distributed Bragg reflector, an element structure suitable for very high-speed modulation can be obtained. In such a surface emitting semiconductor laser device, high-speed modulation of 10 Gbps or more could be easily performed.
[0126]
In each of the above-described embodiments (Examples 1, 3, 4, and 5), a surface-emitting semiconductor laser device in which a crystal is grown on an n-type semiconductor substrate is described. As the surface emitting semiconductor laser device, a p-type semiconductor substrate can be used instead of the n-type semiconductor substrate.
[0127]
FIG. 8 is a diagram showing an example in which the surface emitting semiconductor laser device of Example 3 is realized on a p-type semiconductor substrate, and the surface emitting semiconductor laser device of FIG. 8 is formed on a p-GaAs substrate by MOCVD. Similarly, the crystal was grown. That is, in the surface emitting semiconductor laser device of FIG. 8, first, after growing a p-GaAs buffer layer on a p-GaAs substrate,_0.8Ga_0.236 pairs of p-type semiconductor distributed Bragg reflectors having As / GaAs as a pair are grown, and a GaAs resonator spacer layer, GaInNAs / GaAs multiple quantum well active layer, GaAs spacer layer, Al_0.8Ga_0.226 pairs of n-type semiconductor distributed Bragg reflectors having As / GaAs as a pair are formed by sequentially growing crystals.
[0128]
Here, a linear composition gradient layer (thickness: 30 nm) for reducing electric resistance is provided at each hetero interface of the p-type semiconductor distributed Bragg reflector so as to satisfy the multiple reflection phase condition of the semiconductor distributed Bragg reflector. It is provided in. Also, Al closest to the active layer_0.8Ga_0.2At the hetero interface of As / GaAs, an AlAs selective oxidation layer is similarly provided in consideration of phase conditions. Furthermore, the n-type semiconductor distributed Bragg reflector of the present invention is used for the n-type semiconductor distributed Bragg reflector. That is, a linear composition gradient layer (thickness: 30 nm) for reducing the capacitance is provided as an intermediate layer (semiconductor layer) at each hetero interface of the n-type semiconductor distributed Bragg reflector.
[0129]
In the surface emitting semiconductor laser device of FIG. 8, after the above-described crystal growth, dry etching, selective oxidation, embedding with an insulating resin, and electrode formation are performed as in the third embodiment. However, in the dry etching process, etching is performed halfway through the p-type semiconductor distributed Bragg reflector in order to oxidize the AlAs selective oxidation layer in the p-type semiconductor distributed Bragg reflector.
[0130]
The surface emitting semiconductor laser device of FIG. 8 has a structure suitable for high-speed modulation because the capacitance of the n-type semiconductor distributed Bragg reflector is reduced, similarly to the third embodiment. Could be easily performed.
[0131]
FIG. 9 is a diagram showing another configuration example of the surface emitting semiconductor laser device. The surface emitting semiconductor laser device shown in FIG. 9 is manufactured in the same manner as the surface emitting semiconductor laser device shown in FIG. 8, and a composition gradient layer for reducing electric resistance is provided in the p-type semiconductor distributed Bragg reflector. Is provided, and a composition gradient layer (intermediate layer) for reducing the capacitance is provided in the n-type semiconductor distributed Bragg reflector. However, in the surface emitting semiconductor laser device of FIG. 9, after the dry etching process of the mesa portion, hydrogen ions are implanted in the same manner as in Example 5, except for the mesa portion of the p-type semiconductor distributed Bragg reflector (the resonance region). Area) is increased in resistance. Therefore, by narrowing the hole current path to about the mesa diameter, the capacitance due to the p-type semiconductor distributed Bragg reflector is also reduced, and the structure is more suitable for high-speed modulation than the element of FIG. .
[0132]
In each of the above-described embodiments (Example 1, Example 3, Example 4, and Example 5), the crystal growth of the surface emitting semiconductor laser device is performed by the MOCVD method. Can be used for crystal growth. In addition, as an intermediate layer (a semiconductor layer having a refractive index (forbidden band width) between the two types of semiconductor layers) provided between two types of semiconductor layers having different refractive indexes constituting the semiconductor distributed Bragg reflector, a linear shape is used. Although the composition gradient layer is used, it is also possible to use, as the intermediate layer, a layer having a non-linearly changing composition, or a single layer or a plurality of layers having different refractive indexes. It is also possible to use those that have been done.
[0133]
(Example 6)
FIG. 10 is a diagram illustrating an example of the surface emitting laser array according to the thirteenth embodiment as a sixth embodiment. The surface emitting laser array of FIG. 10 is a monolithic laser array in which 3 × 3 pieces of the above-described surface emitting semiconductor laser device of the present invention are two-dimensionally integrated. In the surface emitting laser array of FIG. 10, p-electrode wiring is individually provided in order to drive each surface emitting semiconductor laser element independently. The surface emitting laser array of FIG. 10 is manufactured by the same procedure and method as those of the first, third, and fifth embodiments.
[0134]
In the surface emitting laser array of FIG. 10, each of the surface emitting semiconductor laser elements constituting the surface emitting laser array has a reduced capacitance due to the n-type semiconductor distributed Bragg reflector. The light emitting laser array has a structure suitable for very high-speed modulation, and in fact, high-speed modulation was possible.
[0135]
(Example 7)
FIG. 11 is a diagram illustrating an example of the surface emitting laser module according to the fourteenth embodiment as Example 7. The surface emitting laser module of FIG. 11 is configured by mounting a one-dimensional monolithic surface emitting laser array, a microlens array, and a fiber array (quartz single mode fiber) on a silicon substrate.
[0136]
Here, the surface emitting laser array is provided with the surface emitting laser array of the thirteenth embodiment facing the fiber, and this surface emitting laser array is formed on a silicon substrate via a microlens array. With the quartz single-mode fiber mounted in the V-groove. The oscillation wavelength of this surface emitting laser array is in the 1.3 μm band, and high-speed optical parallel transmission can be performed by using a quartz single mode fiber.
[0137]
Further, by using the surface emitting laser array of the thirteenth embodiment as the light source of the surface emitting laser module of FIG. 11, high-speed modulation is possible, and a surface emitting laser module capable of high-speed transmission can be obtained.
[0138]
(Example 8)
FIG. 12 is a diagram illustrating a parallel optical interconnection system as an example of the optical interconnection system according to the fifteenth embodiment. In the interconnection system in FIG. 12, the device 1 and the device 2 are connected using an optical fiber array (quartz single mode fiber array). Here, the device 1 on the transmitting side includes a surface emitting laser module using the surface emitting laser array of the fourteenth embodiment and a driving circuit for the module. The device 2 on the receiving side includes a photodiode array module and a signal detection circuit.
[0139]
In the optical interconnection system shown in FIG. 12, high-speed optical parallel transmission becomes possible by using the surface emitting laser module of the fourteenth embodiment. The surface emitting laser module uses a surface emitting laser array using GaInNAs as an active layer, so that stable oscillation can be obtained even when the ambient temperature changes, and an extremely reliable interconnection system can be obtained. Can be configured.
[0140]
In the above example, the parallel optical interconnection system has been described as an example. However, a serial transmission system using a single element may be configured. Further, the present invention can be applied to interconnection between boards, between chips, and within a chip, in addition to between devices.
[0141]
(Example 9)
FIG. 13 is a diagram illustrating an optical LAN system as an example of the optical communication system according to the sixteenth embodiment. The optical LAN system of FIG. 13 is configured using the above-described surface emitting semiconductor laser device, surface emitting laser array, or surface emitting laser module of the present invention.
[0142]
That is, in the optical LAN system of FIG. 13, a light source for optical transmission between the server and the core switch, and / or a light source for optical transmission between the core switch and each switch, and / or the switch and each terminal. The above-described surface-emitting semiconductor laser device, surface-emitting laser array, or surface-emitting laser module of the present invention is used as a light source for optical transmission. Further, the respective devices are coupled by a quartz single-mode fiber or a multi-mode fiber. As a physical layer of such an optical LAN, for example, a gigabit Ethernet such as 1000BASE-LX is used.
[0143]
In the optical LAN system shown in FIG. 13, high-speed communication is enabled by using the above-described surface emitting semiconductor laser device, surface emitting laser array, or surface emitting laser module of the present invention as a light source for optical transmission. Further, in the surface emitting laser of the present invention using GaInNAs as an active layer, stable oscillation can be obtained even when the driving conditions such as the operating environment temperature change, and a highly reliable optical communication system can be configured.
[0144]
【The invention's effect】
As described above, according to the first aspect of the invention, the n-type doped n-type semiconductor distributed Bragg reflector in which two types of semiconductor layers having different refractive indexes are stacked has different refractive indexes. Since an intermediate layer having a refractive index between the two types of semiconductor layers is provided between the two types of semiconductor layers, an n-type semiconductor distributed Bragg reflector with reduced capacitance at the semiconductor heterointerface is provided. Can be provided.
[0145]
According to the second aspect of the present invention, by setting the thickness of the intermediate layer to be greater than 20 nm, the influence of the hetero interface is significantly reduced, and the current-voltage characteristics of the n-type distributed Bragg reflector are improved. And the capacitance at the hetero interface can be reduced.
[0146]
The reason why the capacity of the hetero interface is reduced by the intermediate layer is that the potential distribution such as spikes and notches at the hetero interface is smoothed by the intermediate layer, and the accumulation and depletion of carriers at the interface are suppressed. When no intermediate layer is provided, carriers (electrons) are accumulated and depleted due to spikes and notch-shaped potential distribution generated at the hetero interface, a change in current-voltage characteristics due to measurement conditions, and carrier tunneling at the hetero barrier. There is a problem that the non-linearity of the current-voltage characteristics is considered to be caused by such factors. Further, in addition to this, the generation of capacitance due to the depletion of carriers causes a problem. However, when an intermediate layer having a thickness of 20 nm or more is provided at each interface of the n-type distributed Bragg reflector, these problems can be significantly improved. That is, the change in the current-voltage characteristics and the non-linearity of the current-voltage characteristics due to the measurement conditions can be significantly reduced by the intermediate layer having a thickness larger than 20 nm, and the capacitance due to the hetero interface can be significantly reduced. As described above, an n-type distributed Bragg reflector having excellent electric characteristics can be obtained.
[0147]
According to the third aspect of the present invention, by setting the thickness of the intermediate layer to 30 nm or more, the influence of the hetero interface is reduced more effectively, and the current-voltage characteristics of the n-type distributed Bragg reflector are improved. Can be improved, and the capacitance at the hetero interface can be reduced.
[0148]
The reason why the capacitance of the hetero interface is reduced by the intermediate layer is that the distribution of the potential such as spikes and notches at the hetero interface is smoothed by the intermediate layer, and the accumulation and depletion of carriers at the interface are suppressed. The effect is greater for thicker intermediate layers. Therefore, in particular, by setting the thickness of the intermediate layer to 30 nm or more, there is almost no difference between the CW measurement and the pulse measurement, and the above-described action can be obtained more effectively. As described above, the change in the current-voltage characteristic and the non-linearity of the current-voltage characteristic can be more effectively reduced, and similarly, the capacitance at the hetero interface can be more effectively reduced. As described above, an n-type distributed Bragg reflector having excellent electric characteristics can be obtained.
[0149]
According to a fourth aspect of the present invention, in the n-type distributed Bragg reflector according to the first aspect, the thickness t [nm] of the intermediate layer is set to a reflection wavelength λ [μm] of the distributed Bragg reflector. On the other hand, since the range of 20 <t ≦ (50λ−15) [nm] is satisfied, an n-type distributed Bragg reflector excellent in electric characteristics, in which the influence of the hetero interface is reduced and excellent in electrical characteristics is maintained while maintaining high reflectance. Obtainable. In other words, the distributed Bragg reflector can obtain a higher reflectance as the refractive index difference between the semiconductor layers constituting the reflector is larger and as the interface is steeper. Accordingly, the reflectivity tends to gradually decrease as the thickness of the intermediate layer increases. Therefore, if the thickness of the intermediate layer is too large, the reflectivity of the distributed Bragg reflector drops sharply. However, the effect of flattening the hetero interface is more effectively obtained as the thickness of the intermediate layer is larger. Therefore, it can be seen that there is an optimum range for satisfying both of them as the thickness of the intermediate layer. In other words, by setting the thickness of the intermediate layer within the optimum range of the thickness of the intermediate layer and selecting the thickness of the intermediate layer as 20 <t ≦ (50λ−15) [nm] with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector, It is possible to obtain an n-type distributed Bragg reflector excellent in electric characteristics, in which the influence of the hetero interface is reduced, while maintaining a high reflectance.
[0150]
According to a fifth aspect of the present invention, there is provided a surface emitting semiconductor laser device using the n-type semiconductor distributed Bragg reflector according to any one of the first to fourth aspects. Therefore, it is possible to provide a surface-emitting semiconductor laser device having reduced capacitance and capable of high-speed modulation.
[0151]
According to a sixth aspect of the present invention, in the surface emitting semiconductor laser device provided with an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed therebetween, Since the Bragg reflector is processed in a mesa shape, it is possible to provide a surface-emitting semiconductor laser device having reduced capacitance and capable of high-speed modulation.
[0152]
According to a seventh aspect of the present invention, in the surface emitting semiconductor laser device provided with the n-type semiconductor distributed Bragg reflector and the p-type semiconductor distributed Bragg reflector with the active layer interposed therebetween, the n-type semiconductor distributed Bragg reflector is provided. Since the resistance of the region other than the resonance region of the reflector is increased, the capacitance can be reduced, and a surface emitting semiconductor laser device capable of high-speed modulation can be provided.
[0153]
According to an eighth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. Since the intermediate layer having the refractive index between the two types of semiconductor layers is provided, it is possible to provide a surface emitting semiconductor laser device having reduced capacitance and capable of high-speed modulation.
[0154]
According to the ninth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector is provided between two kinds of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness of the intermediate layer is greater than 20 [nm], so that the path of the electron current is limited and contributes to the capacitance. The area of the n-type semiconductor distributed Bragg reflector can be reduced, the capacitance at the hetero interface of the n-type semiconductor distributed Bragg reflector can be reduced, and high-speed modulation can be performed. That is, as described in the effects of claims 1 and 2, by providing the semiconductor layer at the hetero interface, the distribution of potential at the hetero interface is smoothed as compared with the case where no intermediate layer is provided, Depletion and accumulation of carriers are reduced, and the capacitance caused by depletion can be drastically reduced. Further, as described in claim 6 and claim 7, by limiting the path of the electrons within the mesa region by etching the n-type semiconductor distributed Bragg reflector and increasing the resistance, the semiconductor distribution effectively contributing as a capacitance. The area of the Bragg reflector can be reduced. Therefore, by using them together as in claim 9, it is possible to reduce the capacitance of the element more effectively, and to obtain a structure suitable for very high-speed modulation. The element according to claim 9 can easily perform high-speed modulation of 10 Gbps or more because the capacitance of the n-type semiconductor distributed Bragg reflector is reduced as described above.
[0155]
According to a tenth aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector is provided between two kinds of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness of the intermediate layer is 30 nm or more. , The area of the n-type semiconductor distributed Bragg reflector can be reduced, the capacitance at the hetero interface of the n-type semiconductor distributed Bragg reflector can be reduced, and high-speed modulation can be performed. That is, as described in the effects of the first and second aspects, by providing the semiconductor layer at the hetero interface, it is possible to sufficiently smooth the potential distribution at the hetero interface, and to deplete carriers. , The accumulation is reduced, and the capacitance caused by the depletion can be further reduced. Further, as described in claim 6 and claim 7, by limiting the path of the electrons within the mesa region by etching the n-type semiconductor distributed Bragg reflector and increasing the resistance, the semiconductor distribution effectively contributing as a capacitance. The area of the Bragg reflector can be reduced. Therefore, by using them together as in claim 10, the capacitance of the element can be reduced more effectively, and a structure suitable for very high-speed modulation can be obtained. The element according to claim 10 can easily perform high-speed modulation of 10 Gbps or more because the capacitance of the n-type semiconductor distributed Bragg reflector is reduced as described above.
[0156]
According to the eleventh aspect of the present invention, in the surface emitting semiconductor laser device according to the sixth or seventh aspect, the n-type semiconductor distributed Bragg reflector is provided between two types of semiconductor layers having different refractive indexes. An intermediate layer having a refractive index between the two types of semiconductor layers is provided, and the thickness t [nm] of the intermediate layer is 20 <t with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector. ≦ (50λ−15) [nm], the path of the electron current can be limited, the area of the n-type semiconductor distributed Bragg reflector contributing to the capacitance can be reduced, and further, the n-type semiconductor distributed Bragg reflection can be reduced. The capacitance at the hetero interface of the device can be reduced, and high-speed modulation can be performed. That is, as described in the effects of the first, second, and third aspects, by providing the semiconductor layer at the hetero interface, the potential distribution at the hetero interface is smoothed, and the depletion and accumulation of carriers are reduced. And the capacitance caused by depletion can be significantly reduced. Further, by selecting the thickness of the intermediate layer within the above range, the reflectivity of the n-type distributed Bragg reflector can be kept high, and a surface emitting laser device having a low oscillation threshold current can be obtained.
[0157]
Furthermore, by limiting the path of electrons to the mesa region by etching and increasing the resistance of the n-type semiconductor distributed Bragg reflector, the semiconductor distributed Bragg reflection effectively contributes as a capacitance. The area of the container can be reduced. Therefore, by using them together as in claim 11, the capacitance of the element can be reduced more effectively, and a structure suitable for very high-speed modulation can be obtained. The element according to claim 11 can easily perform high-speed modulation of 10 Gbps or more because the capacitance of the n-type semiconductor distributed Bragg reflector is reduced as described above.
[0158]
According to a twelfth aspect of the present invention, in the surface emitting semiconductor laser device according to any one of the fifth to eleventh aspects, the active layer is made of a group III material and a group V material. Since the group III material of the active layer is any or all of Ga and In and the group V material of the active layer is any or all of As, N, and Sb, the capacitance is And a surface emitting semiconductor laser device in a long wavelength band capable of high-speed modulation can be provided.
[0159]
According to a thirteenth aspect of the present invention, there is provided a surface emitting laser array comprising the surface emitting semiconductor laser device according to any one of the fifth to twelfth aspects. A surface emitting laser array with reduced capacitance and capable of high-speed modulation can be provided.
[0160]
According to a fourteenth aspect of the present invention, the surface emitting semiconductor laser device according to any one of the fifth to twelfth aspects or the surface emitting laser array according to the thirteenth aspect is used. Therefore, a surface emitting laser module capable of high-speed optical communication and light transmission can be provided.
[0161]
According to a fifteenth aspect of the present invention, the surface emitting semiconductor laser device according to any one of the fifth to twelfth aspects, the surface emitting laser array according to the thirteenth aspect, or the fourteenth aspect. Since the optical interconnection system is configured using the surface emitting laser module described above, it is possible to provide an optical interconnection system capable of high-speed, large-capacity optical transmission.
[0162]
According to a sixteenth aspect of the present invention, the surface emitting semiconductor laser device according to any one of the fifth to twelfth aspects, the surface emitting laser array according to the thirteenth aspect, or the fourteenth aspect. Since the optical communication system is configured using the surface emitting laser module described above, it is possible to provide an optical communication system capable of high-speed, large-capacity optical transmission.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an example of an n-type semiconductor distributed Bragg reflector according to a first embodiment.
FIG. 2 is a diagram showing an example of a composition gradient layer.
FIG. 3 is a diagram illustrating an example of a surface emitting semiconductor laser device according to second and sixth embodiments.
FIG. 4 is a diagram illustrating an example of a surface emitting semiconductor laser device according to third and fifth embodiments.
FIG. 5 is a diagram showing an example of an n-type semiconductor distributed Bragg reflector.
FIG. 6 is a diagram illustrating an example of the surface emitting semiconductor laser device according to the fourth and fifth embodiments.
FIG. 7 is a diagram illustrating an example of an n-type semiconductor distributed Bragg reflector.
FIG. 8 is a diagram showing an example in which the surface emitting semiconductor laser device of Example 2 is realized on a p-type semiconductor substrate.
FIG. 9 is a diagram showing another configuration example of the surface emitting semiconductor laser device.
FIG. 10 is a diagram illustrating an example of a surface emitting laser array according to a seventh embodiment.
FIG. 11 is a diagram illustrating an example of a surface emitting laser module according to an eighth embodiment.
FIG. 12 is a diagram illustrating a parallel optical interconnection system as an example of an optical interconnection system according to a ninth embodiment.
FIG. 13 is a diagram illustrating an optical LAN system as an example of the optical communication system according to the tenth embodiment.
FIG. 14 is a diagram showing current-voltage characteristics to show the effect of a hetero interface on device characteristics.
FIG. 15 is a diagram showing an element including an n-type semiconductor distributed Bragg reflector made of AlAs / GaAs.
FIG. 16 is a diagram showing current-voltage characteristics when a linear composition gradient layer is provided as an intermediate layer at each interface of AlAs / GaAs of an n-type semiconductor distributed Bragg reflector in an element having a structure similar to that of FIG. .
FIG. 17 is a diagram showing a differential coefficient of a change in reflectance with respect to a thickness of a composition gradient layer of a distributed Bragg reflector made of AlAs / GaAs in each wavelength band.
FIG. 18 is a diagram illustrating an example of an n-type semiconductor distributed Bragg reflector according to the third embodiment.

Claims (16)

In an n-type doped n-type semiconductor distributed Bragg reflector in which two types of semiconductor layers having different refractive indexes are stacked, between two types of semiconductor layers having different refractive indexes, N-type distributed Bragg reflector comprising an intermediate layer having a refractive index of The n-type distributed Bragg reflector according to claim 1, wherein the thickness of the intermediate layer is greater than 20 [nm]. 2. The n-type distributed Bragg reflector according to claim 1, wherein said intermediate layer has a thickness of 30 nm or more. 2. The n-type semiconductor distributed Bragg reflector according to claim 1, wherein the thickness t [nm] of the intermediate layer is 20 <t ≦ (50λ-15) with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector. An n-type distributed Bragg reflector in the range of [nm]. A surface emitting semiconductor laser device, comprising the n-type semiconductor distributed Bragg reflector according to claim 1. In a surface emitting semiconductor laser device provided with an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed therebetween, the n-type distributed Bragg reflector is processed into a mesa shape. A surface emitting semiconductor laser device characterized by the above-mentioned. In a surface emitting semiconductor laser device provided with an n-type distributed Bragg reflector and a p-type distributed Bragg reflector with an active layer interposed therebetween, regions other than the resonance region of the n-type distributed Bragg reflector have higher resistance. A surface emitting semiconductor laser device characterized in that: 8. The surface emitting semiconductor laser device according to claim 6, wherein said n-type semiconductor distributed Bragg reflector has a refractive index between two semiconductor layers having different refractive indexes. A surface emitting semiconductor laser device comprising an intermediate layer having the following formula: 8. The surface emitting semiconductor laser device according to claim 6, wherein said n-type semiconductor distributed Bragg reflector has a refractive index between two semiconductor layers having different refractive indexes. A surface emitting semiconductor laser device, wherein an intermediate layer having the following formula is provided, and the thickness of the intermediate layer is larger than 20 [nm]. 8. The surface emitting semiconductor laser device according to claim 6, wherein said n-type semiconductor distributed Bragg reflector has a refractive index between two semiconductor layers having different refractive indexes. A surface emitting semiconductor laser device, wherein an intermediate layer having the following formula is provided, and the thickness of the intermediate layer is 30 [nm] or more. 8. The surface emitting semiconductor laser device according to claim 6, wherein said n-type semiconductor distributed Bragg reflector has a refractive index between two semiconductor layers having different refractive indexes. And the thickness t [nm] of the intermediate layer is in the range of 20 <t ≦ (50λ−15) [nm] with respect to the reflection wavelength λ [μm] of the distributed Bragg reflector. A surface emitting semiconductor laser device, comprising: The surface emitting semiconductor laser device according to any one of claims 5 to 11, wherein the active layer is made of a group III material and a group V material, and the group III material of the active layer is Ga, A surface-emitting semiconductor laser device comprising: any or all of In; and a group V material of the active layer is any or all of As, N, Sb, and P. A surface-emitting laser array comprising the surface-emitting semiconductor laser device according to claim 5. A surface emitting laser module comprising the surface emitting semiconductor laser device according to any one of claims 5 to 12, or the surface emitting laser array according to claim 13. A surface emitting semiconductor laser device according to any one of claims 5 to 12, a surface emitting laser array according to claim 13, or a surface emitting laser module according to claim 14. Optical interconnection system. A surface emitting semiconductor laser device according to any one of claims 5 to 12, a surface emitting laser array according to claim 13, or a surface emitting laser module according to claim 14. Optical communication system.

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