JP3850288B2 - Semiconductor laser device and manufacturing method thereof - Google Patents

Description

となり、その外側となる低屈折率領域の幅がdc/2となるように、さらに複数コアの各コア間に設けられた高屈折率領域の幅db₂が
【数２】

となるようにすることが望ましいことが報告されている。
【０００３】
【発明が解決しようとする課題】
上記特許に例示されている半導体レーザ素子は、再成長技術を要する構造であって、さらに、その際、InGaP層、InAlP層およびGaAs層が再成長前に表面に露出する構造であるため、再成長時の昇温過程でPとAsの表面での相互拡散が生じ、再成長不良を起こしやすいという欠点があり、実用化に適していない。
【０００４】
本発明は上記事情に鑑みて、ＡＲＲＯＷ構造を有する半導体レーザ素子であって、低出力から高出力まで信頼性の高い半導体レーザ素子およびその半導体レーザ素子を容易に製造する方法を提供することを目的とするものである。
【０００５】
【課題を解決するための手段】
本発明の半導体レーザ素子は、第一導電型ＧａＡｓ基板上に、第一導電型のＩｎ_0.49Ｇａ_0.51ＰまたはＡｌ_z1Ｇａ_1-z1Ａｓ（ただし、0.2≦z1≦0.8）からなる下部クラッド層、第一導電型またはアンドープのＧａＡｓ下部光導波層、Ｉｎ_x3Ｇａ_1-x3Ａｓ_1-y3Ｐ_y3圧縮歪量子井戸活性層（ただし、0.49y3＜x3≦0.4,0≦y3≦0.1）、第二導電型またはアンドープのＧａＡｓ上部光導波層をこの順に積層してなる積層体上に、共振器の共振方向にストライプ状に、電流注入領域および該電流注入領域の両側にそれぞれ所定距離離れた領域に開口を有する第二導電型Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層（ただし、0≦x8≦1）および第一導電型ＧａＡｓ電流狭窄層をこの順に備え、第一導電型ＧａＡｓ電流狭窄層上および電流注入領域以外の領域の前記開口に露出する前記上部光導波層上に、第一導電型あるいは第二導電型Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層（ただし、0≦x9≦1）および第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層をこの順に備え、第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層上および電流注入領域の開口に露出する上部光導波層上に、第二導電型Ａｌ_z1Ｇａ_1-z1Ａｓ上部クラッド層および第二導電型ＧａＡｓコンタクト層を備えてなることを特徴とするものである。
【０００６】
第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層上に、第一導電型あるいは第二導電型のＧａＡｓキャップ層が設けられていてもよい。
【０００７】
Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層と第一導電型ＧａＡｓ電流狭窄層との間に第二導電型ＧａＡｓ層が設けられていてもよい。
【０００８】
なお、電流注入領域の幅は３μｍ以上であることが望ましい。
【０００９】
第一導電型ＧａＡｓ電流狭窄層の積層方向の途中に、活性層よりバンドギャップが小さいＩｎＧａＡｓ量子井戸層を備えていてもよい。
【００１０】
本発明の半導体レーザ素子の製造方法は、第一導電型ＧａＡｓ基板上に、第一導電型のＩｎ_0.49Ｇａ_0.51ＰまたはＡｌ_z1Ｇａ_1-z1Ａｓ（ただし、0.2≦z1≦0.8）からなる下部クラッド層、第一導電型またはアンドープのＧａＡｓ下部光導波層、Ｉｎ_x3Ｇａ_1-x3Ａｓ_1-y3Ｐ_y3圧縮歪量子井戸活性層（ただし、0.49y3＜x3≦0.4,0≦y3≦0.1）、第二導電型またはアンドープのＧａＡｓ上部光導波層、第二導電型Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層（ただし、0≦x8≦1）、第一導電型ＧａＡｓ電流狭窄層をこの順に積層し、第一導電型ＧａＡｓ電流狭窄層と第二導電型Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層とを、電流注入領域および該電流注入領域の両側から所定距離離れた領域を共振器方向にストライプ状に除去して上部光導波層を露出させ、Ａｓ雰囲気で昇温した後、第一導電型ＧａＡｓ電流狭窄層上および前記露出された上部光導波層上に、再成長により第一導電型あるいは第二導電型Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層（ただし、0≦x9≦1）および第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層をこの順に積層し、電流注入領域の、第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層およびＩｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層を除去して、上部光導波層を露出させ、Ａｓ雰囲気で昇温した後、第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層上および露出された上部光導波層上に、再成長により第二導電型Ａｌ_z1Ｇａ_1-z1Ａｓ上部クラッド層および第二導電型ＧａＡｓコンタクト層をこの順に積層することを特徴とするものである。
【００１１】
第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層の上に第一導電型あるいは第二導電型のＧａＡｓ層を成長してもよい。
【００１２】
なお、上記第一導電型と第二導電型とは、逆極性を示すものであり、例えば、第一導電型がｎ型であれば、第二導電型はｐ型であることを示す。
【００１３】
また、上記アンドープとは導電性不純物が導入されていないことを示す。
【００１４】
【発明の効果】
本発明の半導体レーザ素子によれば、上述のような層構成を備えたことにより、活性層に水平な方向において、ストライプ状の電流注入開口によって規定されるコア領域を中心として、その両側にコア領域の等価屈折率よりも高い等価屈折率である高屈折率領域、その外側にコア領域と同等の等価屈折率である低屈折率領域、さらにその外側に第二の高屈折率領域を備えた、いわゆるＡＲＲＯＷ構造を構成したものとすることができる。
【００１５】
このＡＲＲＯＷ構造を備えたことにより、ＡＲＲＯＷ構造を備えない素子と比較して、ストライプ幅を広くしても横モード制御がなされた単峰性のビームを発振することができる。すなわち、ＡＲＲＯＷ構造を備えない素子においては、横モード制御を行うために、ストライプ幅を３μｍより小さくする必要があったため、それに応じて活性領域幅が制限され、高出力化を図ると活性層への光密度が高くなり端面劣化を引き起こすために高出力発振を行うことができなかった。しかし、上述したような等価屈折率分布のＡＲＲＯＷ構造を有する素子であるため、幅広のストライプ幅の領域に良好な光閉じ込めを行うことができ、幅広の活性領域からの横基本モード発振が可能となる。なお、３μｍ以上の幅広の活性領域を備えれば活性層の光密度が低減できるので、端面の光吸収再結合による温度上昇を低減でき、ＡＲＲＯＷ構造を備えない素子と比較して高出力の光ビームを得ることができる。
【００１６】
また特に、光導波層とＧａＡｓ電流狭窄層とにＧａＡｓを用いたことにより、高屈折率領域の屈折率の制御が容易であるので、水平方向の等価屈折率分布の制御性が高いＡＲＲＯＷ構造を得ることができる。
【００１７】
また、第一導電型ＧａＡｓ電流狭窄層の積層方向の途中に、活性層よりバンドギャップの小さいＩｎＧａＡｓ量子井戸層を備えたものとすれば、ＩｎＧａＡｓ量子井戸層において光吸収が起こるために基本横モード発振の利得を高くすることができる。
【００１８】
本発明の半導体レーザ素子の製造方法によれば、活性層に水平な方向において、ストライプ状の電流注入開口によって規定されるコア領域を中心として、その両側にコア領域の等価屈折率よりも高い等価屈折率である高屈折率領域、その外側にコア領域と同等の等価屈折率である低屈折率領域、さらにその外側に第二の高屈折率領域を備えた、いわゆるＡＲＲＯＷ構造を備えた半導体レーザ素子を高精度にかつ容易に製造することができる。
【００１９】
また、再成長前に露出する層がほぼＡｌＧａＡｓ電流狭窄層とＧａＡｓ上部光導波層のみとなり、一回の再成長前に露出する層にＡｓとＰとが同時に存在することがないので両者の相互拡散を抑制し、再成長の結晶品質を向上させることができる。
【００２０】
また、エッチング阻止層をＩｎＧａＰ層にすることにより、ＧａＡｓエッチング精度が高くなり、ＡＲＲＯＷ構造に必要な屈折率分布を高精度に形成することができる。
【００２１】
また、第一導電型Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層上に、第一導電型あるいは第二導電型のＧａＡｓキャップ層を成長することにより、上部クラッド層の再成長の際にＡｌＧａＡｓ電流狭窄層の露出が少ないため、Ａｌの酸化を低減することができるので、結晶品質が良好となり信頼性を向上させることができる。
【００２２】
【発明の実施の形態】
以下、本発明の実施の形態を図面を用いて詳細に説明する。
【００２３】
本発明の第１の実施の形態による半導体レーザ素子について説明する。図１にその半導体レーザ素子の断面図を示す。
【００２４】
図１に示すように、本実施の形態の半導体レーザ素子は、ｎ−ＧａＡｓ基板１上に、ｎ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ下部クラッド層２（0.2≦z1≦0.8）、ｎ−またはi−ＧａＡｓ下部光導波層３、Ｉｎ_x3Ｇａ_1-x3Ａｓ_1-y3Ｐ_y3圧縮歪量子井戸活性層（0.49y3＜x3≦0.4,0≦y3≦0.1）４、ｐ−またはi−ＧａＡｓ上部光導波層５を積層した積層体上に、共振器方向に延びるストライプ状に、幅dcの電流注入領域20および該電流注入領域20の両側にそれぞれdb₁離れたdc/2幅の領域に開口を有するｐ−Ｉｎ_x8Ｇａ_{１ -x8}Ｐ第一エッチング阻止層６（0≦x8≦１）およびｎ−ＧａＡｓ電流狭窄層７を備え、該ｎ−ＧａＡｓ電流狭窄層７上および電流注入領域20以外の開口に露出するｐ−ＧａＡｓ上部光導波層５上に、ｐ−Ｉｎ_x9Ｇａ_{１ -x9}Ｐ第二エッチング阻止層８（0≦x9≦1）を備え、該第二エッチング阻止層８上に、電流注入領域20に開口を有するｎ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ電流狭窄層９を備え、さらに、このｎ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ電流狭窄層９上および電流注入領域20の開口に露出するＧａＡｓ上部光導波層５上に、ｐ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ上部クラッド層10およびｐ−ＧａＡｓコンタクト層11を備えてなるものである。
【００２５】
本実施の形態で、下部クラッド層の組成をＧａＡｓに格子整合するp−Ｉｎ_0.49Ｇａ_0.51Ｐとしてもよく、同様にＡＲＲＯＷ構造の形成に必要な屈折率分布が得られる。
【００２６】
この半導体レーザ素子は、上述の層構成により、活性層に水平な方向において、ストライプ状の電流注入領域20によって規定されるコア領域を中心として、その両側にコア領域の等価屈折率ncよりも高い等価屈折率nbである高屈折率領域、その外側にコア領域と同等の等価屈折率ncである低屈折率領域を備え、さらにその外側に等価屈折率nbである第二の高屈折率領域を備えた、図２に示すような等価屈折率分布が形成されている。
【００２７】
なお、前述のとおり、発振波長をλとし、コア領域の等価屈折率をnc、コア領域の両側の高屈折率領域の屈折率をnbとしたとき、コア領域の両側の高屈折率領域の幅db₁は、
【数３】

であることが望ましい。なお、ｍは正の整数である。さらに、この高屈折率領域の外側に設けられたdc/2幅の低屈折率領域により、光出力の横方向（等価屈折率分布を有する方向）への漏れを抑制し、回折限界の単峰性の発振が得られる良好なＡＲＲＯＷ構造を形成することができる。
【００２８】
次に、本発明の第２の実施の形態による半導体レーザ素子について説明する。その半導体レーザ素子の断面図を図３に示す。なお、第１の実施の形態と同等の層には同符号を付し詳細な説明を省略する（以下、同様とする）。本実施の形態の半導体レーザ素子は、ｎ−ＧａＡｓ電流狭窄層７の積層方向の途中に量子井戸活性層４よりもバンドギャップが小さいInGaAs量子井戸層14を備えてなるものである。このInGaAs量子井戸層14を備えた素子は、InGaAs量子井戸層14において光吸収が起こるために基本横モード発振の利得が高くなる。
【００２９】
また、本発明は、上述のような単一コアのＡＲＲＯＷ構造に限るものではなく、マルチコアを有する構造であってもよい。マルチコアのＡＲＲＯＷ構造とする場合には、活性層に水平な方向における等価屈折率分布が図４のようになるようにする。この場合、幅dcの複数のコア領域の両端に配される高屈折率領域の幅db₁は上式を満たし、各コア領域間の高屈折率領域は、その幅db₂が、
【数４】

を満たすことが望ましい。なお、ｍは正の整数である。
【００３０】
次に、本発明の第３の実施の形態による半導体レーザ素子について説明する。その半導体レーザ素子の断面図を図５に示す。上述のようにマルチコアを有するＡＲＲＯＷ構造を有する素子の断面図を示す。本実施の形態は第１の実施の形態の半導体レーザ素子と層構成は同一であるが、幅db₂間隔で設けられた幅dcの３つの電流注入領域21a,21b,21cおよび該両端の電流注入領域21a,21cの両側にそれぞれdb₁離れたdc/2幅の領域に開口を有するｐ−Ｉｎ_x8Ｇａ_{１ -x8}Ｐ第一エッチング阻止層６およびｎ−ＧａＡｓ電流狭窄層７を備えたことにより、３つのコア領域を有するものである点で異なる。このようにマルチコアにすることによりさらに高出力化が可能となる。
【００３１】
なお、上記半導体層の成長法しては、固体あるいはガスを原料とする分子線エピタキシャル成長法を用いてもよい。上記構造はｎ型層を最初に成長しているが、ｐ型層から成長しても良く、その場合、導電性を反転するだけでよい。
【００３２】
活性層は多重量子井戸構造でもよい。また、活性層を挟むように、活性層の圧縮歪を補償する引張り歪ｉ-Ｉｎ_x4Ｇａ_1-x4Ａｓ_1-y4Ｐ_y4（0≦x4＜0.49y4，0＜y4≦0.4）障壁層を設けてもよい。これにより活性層近傍トータル歪を低減し、活性層の結晶性を向上させることができる。
【００３３】
なお、ＧａＡｓ上部光導波層５の厚みが100ｎｍ以下である場合、ｎ−ＧａＡｓ電流狭窄層７とｐ−Ｉｎ_x8Ｇａ_{１ -x8}Ｐ第一エッチング阻止層６との間にp−ＧａＡｓ層を設けることにより、ｎ−ＧａＡｓ電流狭窄層７からの電流の漏れを防止することができるので、電気特性を向上させることができる。
【００３４】
また、発振時の端面での光吸収による再結合非発光電流を抑制するために、共振器端面近傍のｐ−ＧａＡｓコンタクト層11を除去することにより、より高出力化を図ることができる。
【００３５】
【実施例】
以下に、図１に示した半導体レーザ素子の具体的な層構成およびその製造方法の一実施例を図６を参照して説明する。なお、成長用原料として、トリメチルガリウム（TMG）、トリメチルインジュウム（TMI）、トリメチルアルミニウム（TMA）、アルシンおよびフォスフィンを原料とし、n型ドーパントガスとして、シランガスを用い、p型ドーパントとしてジメチルジンク（DMZ）を用いる。
【００３６】
図６（ａ）に示すように、有機金属気相成長法により（００１）ｎ−ＧａＡｓ基板１上に、ｎ−Ａｌ_z1Ｇａ_1-z1Ａｓ下部クラッド層２、ｎまたはｉ−ＧａＡｓ下部光導波層３、ｉ-Ｉｎ_x3Ｇａ_1-x3Ａｓ_1-y3Ｐ_y3圧縮歪量子井戸活性層４（0.49y3＜x3≦0.4,0≦y3≦0.１，厚さ5から20ｎｍ程度）、ｐまたはｉ−ＧａＡｓ上部光導波層５、ｐ−Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層６、ｎ−ＧａＡｓ電流狭窄層７（0.5μｍ）を積層する。なおここで、x3=0.2, y3=0とすれば発振波長は980ｎｍとなり、また活性層の組成を変化させることにより発振波長を、900＜λ＜1200（ｎｍ）の範囲で制御することができる。
【００３７】
次に、図６（ｂ）に示すように、フォトリソグラフィ法によって幅６μｍのストライプ状の電流注入領域20、およびその両側に1.8μｍの間隔を空けて３μｍ幅の領域のレジストパターンを開口し、レジストをマスクとして硫酸と過酸化水素水系のエッチング液でｎ−ＧａＡｓ電流狭窄層７をエッチングした。この時、自動的にｐ−Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層６でエッチングが停止した。引き続きレジストを除去し、塩酸系エッチング液で、ｐ−Ｉｎ_x8Ｇａ_1-x8Ｐ第一エッチング阻止層６をエッチングした。この時自動的にＧａＡｓ上部光導波層５でエッチングが停止し、ＧａＡｓ上部光導波層５が露出する。引き続き、Ａｓ雰囲気で昇温を行い、その後、順次ガス切り替えを行うことにより、露出されたＧａＡｓ上部光導波層５およびｎ−ＧａＡｓ電流狭窄層７上にｐ−Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層８（0≦x9≦1）およびｎ−Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層９（厚さ0.5μｍ）をこの順に成長した。なお、第二エッチング阻止層８はｎ−Ｉｎ_x9Ｇａ_1-x9Ｐでもよい。
【００３８】
次に、図６（ｃ）に示すように、レジストを塗布し、電流注入領域のレジストを除去し、硫酸と過酸化水素水系のエッチング液で、レジストをマスクとしてｎ−Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層９をエッチングした。この時、自動的に、ｐ−Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層８で自動的にエッチングが停止した。レジストを除去後、塩酸系のエッチング液で、ｐ−Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層８を除去した。この時、自動的にＧａＡｓ上部光導波層５でエッチングが停止し、ストライプ領域に電流注入領域が形成された。
【００３９】
次に、図６（ｄ）に示すように、再成長表面がＧａＡｓ及びＡｌＧａＡｓとなった状態でＡｓ雰囲気で昇温し、ｐ−Ａｌ_z1Ｇａ_1-z1Ａｓ上部クラッド層10およびｐ−ＧａＡｓコンタクト層11を形成した。引き続き、ｐ側電極12を形成後、基板を研磨し、ｎ側電極13を形成し、試料をへき開して形成した共振器面の一方に高反射率コート、他方に低反射コートを行い、その後、チップ化して半導体レーザ素子を形成する。
【００４０】
なお、ｎ−Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層９を積層した後に第一導電型あるいは第二導電型のＧａＡｓキャップ層を積層してもよい。そして、このＧａＡｓキャップ層のパターニングはｎ−Ａｌ_z1Ｇａ_1-z1Ａｓ電流狭窄層９をエッチングする際にエッチングできる。
【００４１】
本発明の半導体レーザ素子は、高出力まで信頼性が高いので、高速な情報・画像処理及び通信、計測、医療、印刷の分野での光源として応用可能である。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態による半導体レーザ素子を示す断面図
【図２】単一コアのＡＲＲＯＷ構造を備えた半導体レーザ素子の活性層に水平方向の等価屈折率分布を示す図
【図３】本発明の第２の実施の形態による半導体レーザ素子を示す断面図
【図４】マルチコアを有するＡＲＲＯＷ構造を備えた半導体レーザ素子における活性層に水平方向の等価屈折率分布を示す図
【図５】本発明の第３の実施の形態による半導体レーザ素子を示す断面図
【図６】本発明の一実施例の半導体レーザ素子を示す断面図
【符号の説明】
１ ｎ−ＧａＡｓ基板
２ ｎ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ下部クラッド層
３ ｎ−またはi−ＧａＡｓ下部光導波層
４ Ｉｎ_x3Ｇａ_1-x3Ａｓ_1-y3Ｐ_y3圧縮歪量子井戸活性層
５ ｐ−またはi−ＧａＡｓ上部光導波層
６ ｐ−Ｉｎ_x8Ｇａ_{１ -x8}Ｐ第一エッチング阻止層
７ ｎ−ＧａＡｓ電流狭窄層
８ ｐ−Ｉｎ_x9Ｇａ_1-x9Ｐ第二エッチング阻止層
９ ｎ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ電流狭窄層
10 ｐ−Ａｌ_z1Ｇａ_{１ -z1}Ａｓ上部クラッド層
11 ｐ−ＧａＡｓコンタクト層
12 ｐ側電極
13 ｎ側電極
20 電流注入領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser device, and more particularly to a semiconductor laser device having an oscillation wavelength of 980 nm band and an ARROW structure.
[0002]
[Prior art]
As a light source for exciting an optical fiber amplifier, a high-power semiconductor laser having a highly reliable diffraction-limited high-quality beam is expected. Currently, as a semiconductor laser capable of high-power diffraction limited oscillation in the 980 nm band, US Pat. No. 5,606,570, non-resonant reflection using InGaAs as an active layer, InGaAlP as a current confinement layer, and GaAs as a high refractive index medium. It has been reported that a semiconductor laser device having an optical confinement (Antiresonant Reflecting Optical Waveguide) structure (hereinafter referred to as an ARROW structure) is capable of high output. The ARROW structure is composed of a plurality of low refractive index core regions, a high refractive index region provided between and outside the core regions, and substantially the same as the core region provided further outside the core region and the high refractive index region. A low refractive index region having a refractive index and a high refractive index region provided on the outermost side are provided, and light confinement is performed in each core region. According to this structure, the high refractive index regions provided on both outer sides of the core region act as a reflector for the fundamental transverse mode, and further the light leakage is suppressed by the low refractive index region provided on the outer side. Thus, basic transverse mode control can be performed. When performing the fundamental transverse mode control, the oscillation wavelength is λ, the equivalent refractive index of the core region is nc, the core region width is dc, and the equivalent refractive index of the high refractive index region provided on both outer sides of the core region is When the width is nb and db ₁ , respectively
[Expression 1]

And the width db ₂ of the high refractive index region provided between the cores of the plurality of cores so that the width of the low refractive index region on the outside is dc / 2.

It is reported that it is desirable to
[0003]
[Problems to be solved by the invention]
The semiconductor laser device exemplified in the above-mentioned patent has a structure that requires a regrowth technique, and at that time, the InGaP layer, the InAlP layer, and the GaAs layer are exposed on the surface before the regrowth. During the temperature rise process during growth, mutual diffusion occurs on the surface of P and As, which is liable to cause regrowth failure, and is not suitable for practical use.
[0004]
In view of the above circumstances, an object of the present invention is to provide a semiconductor laser element having an ARROW structure, which is highly reliable from low output to high output, and a method for easily manufacturing the semiconductor laser element. It is what.
[0005]
[Means for Solving the Problems]
A semiconductor laser device according to the present invention includes a lower cladding layer made of In _0.49 Ga _0.51 P or Al _z1 Ga _{1 -z1} As (where 0.2 ≦ z1 ≦ 0.8) on a first conductivity type GaAs substrate, a first conductivity type or an undoped GaAs lower optical waveguide layer _{of, in x3 Ga 1-x3 As} 1-y3 P y3 compressive strain quantum well active layer (where, 0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1), the second On a laminate formed by laminating conductive or undoped GaAs upper optical waveguide layers in this order, in a stripe shape in the resonance direction of the resonator, in a current injection region and a region separated by a predetermined distance on both sides of the current injection region. A first conductivity type GaAs current confinement layer comprising an opening having a second conductivity type In _x8 Ga _1-x8 P first etching blocking layer (where 0 ≦ x8 ≦ 1) and a first conductivity type GaAs current confinement layer in this order The opening in the region other than the upper and current injection region Said upper optical waveguide layer on the exposed first conductivity type or the second conductivity type In _x9 Ga _1-x9 P second etching stop layer (where, 0 ≦ x9 ≦ 1) and the first conductivity type Al _z1 Ga _{1- z1} As current includes a blocking layer in this order, the upper optical waveguide layer that is exposed to the first conductivity type Al _z1 Ga _1-z1 As current opening of confinement layer and the current injection region, the second conductivity type Al _z1 Ga _{1- A z1} As upper cladding layer and a second conductivity type GaAs contact layer are provided.
[0006]
A GaAs cap layer of the first conductivity type or the second conductivity type may be provided on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer.
[0007]
A second conductivity type GaAs layer may be provided between the In _x8 Ga _1-x8 P first etching stop layer and the first conductivity type GaAs current confinement layer.
[0008]
The width of the current injection region is desirably 3 μm or more.
[0009]
An InGaAs quantum well layer having a band gap smaller than that of the active layer may be provided in the middle of the stacking direction of the first conductivity type GaAs current confinement layer.
[0010]
The method of manufacturing a semiconductor laser device according to the present invention comprises a first conductive type In _0.49 Ga _0.51 P or Al _z1 Ga _{1 -z1} As (provided that 0.2 ≦ z1 ≦ 0.8) on a first conductive type GaAs substrate. cladding layer, the first conductive type or an undoped GaAs lower optical waveguide layer _{of, in x3 Ga 1-x3 As} 1-y3 P y3 compressive strain quantum well active layer (where, 0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1) The second conductive type or undoped GaAs upper optical waveguide layer, the second conductive type In _x8 Ga _1-x8 P first etching blocking layer (where 0 ≦ x8 ≦ 1), the first conductive type GaAs current confinement layer The first conductivity type GaAs current confinement layer and the second conductivity type In _x8 Ga _1-x8 P first etching stop layer are laminated in order, and the current injection region and a region separated by a predetermined distance from both sides of the current injection region are resonated. The upper optical waveguide layer is exposed by striping in the direction of the vessel, and As After the temperature is raised in the atmosphere, the first conductive type or second conductive type In _x9 Ga _1-x9 P second etching is performed on the first conductive type GaAs current confinement layer and the exposed upper optical waveguide layer by regrowth. blocking layer (where, 0 ≦ x9 ≦ 1) and a first conductivity type Al _z1 Ga _1-z1 As current confinement layer are laminated in this order, the current injection region, a first conductivity type Al _z1 Ga _1-z1 As current confinement Layer and In _x9 Ga _1-x9 P second etching blocking layer are exposed to expose the upper optical waveguide layer, and the temperature is raised in the As atmosphere, and then on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer A second conductivity type Al _z1 Ga _{1 -z1} As upper cladding layer and a second conductivity type GaAs contact layer are laminated in this order on the exposed upper optical waveguide layer by re-growth.
[0011]
A GaAs layer of the first conductivity type or the second conductivity type may be grown on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer.
[0012]
The first conductivity type and the second conductivity type indicate opposite polarities. For example, if the first conductivity type is n-type, it indicates that the second conductivity type is p-type.
[0013]
The undoped means that no conductive impurities are introduced.
[0014]
【The invention's effect】
According to the semiconductor laser device of the present invention, since the layer structure as described above is provided, the core region is defined on the both sides of the core region defined by the stripe-shaped current injection opening in the direction horizontal to the active layer. A high refractive index region having an equivalent refractive index higher than the equivalent refractive index of the region, a low refractive index region having an equivalent refractive index equivalent to that of the core region on the outside thereof, and a second high refractive index region on the outside thereof A so-called ARROW structure can be formed.
[0015]
By providing this ARROW structure, it is possible to oscillate a unimodal beam in which the transverse mode control is performed even if the stripe width is widened, as compared with an element not having the ARROW structure. That is, in the element not having the ARROW structure, the stripe width needs to be smaller than 3 μm in order to perform the transverse mode control. Therefore, the active region width is limited accordingly, and when the output is increased, the active layer is moved to the active layer. High light oscillation could not be carried out because the light density of the device increased and caused the end face to deteriorate. However, since it is an element having an ARROW structure with an equivalent refractive index distribution as described above, it is possible to perform good optical confinement in a wide stripe width region and to enable transverse fundamental mode oscillation from a wide active region. Become. In addition, since the light density of the active layer can be reduced if a wide active region of 3 μm or more is provided, the temperature rise due to light absorption recombination at the end face can be reduced, and high output light compared with an element not having the ARROW structure. A beam can be obtained.
[0016]
In particular, since GaAs is used for the optical waveguide layer and the GaAs current confinement layer, it is easy to control the refractive index in the high refractive index region. Therefore, an ARROW structure with high controllability of the horizontal equivalent refractive index distribution is provided. Obtainable.
[0017]
If an InGaAs quantum well layer having a band gap smaller than that of the active layer is provided in the middle of the stacking direction of the first conductivity type GaAs current confinement layer, light absorption occurs in the InGaAs quantum well layer, so that the fundamental transverse mode is obtained. The oscillation gain can be increased.
[0018]
According to the method for manufacturing a semiconductor laser device of the present invention, in the direction horizontal to the active layer, the core region defined by the stripe-shaped current injection opening is the center and the equivalent refractive index higher than the equivalent refractive index of the core region is formed on both sides thereof. A semiconductor laser having a so-called ARROW structure having a high refractive index region which is a refractive index, a low refractive index region having an equivalent refractive index equivalent to that of the core region on the outer side, and a second high refractive index region on the outer side. The element can be easily manufactured with high accuracy.
[0019]
In addition, the layers exposed before the regrowth are almost only the AlGaAs current confinement layer and the GaAs upper optical waveguide layer, and As and P do not exist at the same time in the layer exposed before one regrowth. Diffusion can be suppressed and the regrowth crystal quality can be improved.
[0020]
Further, by using an InGaP layer as the etching stopper layer, the GaAs etching accuracy is increased, and the refractive index distribution necessary for the ARROW structure can be formed with high accuracy.
[0021]
Further, by growing a GaAs cap layer of the first conductivity type or the second conductivity type on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer, the AlGaAs current confinement is performed during the regrowth of the upper clad layer. Since the exposure of the layer is small, the oxidation of Al can be reduced, so that the crystal quality is improved and the reliability can be improved.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
A semiconductor laser device according to the first embodiment of the present invention will be described. FIG. 1 shows a cross-sectional view of the semiconductor laser device.
[0024]
As shown in FIG. 1, the semiconductor laser device according to the present embodiment has an n-Al _z1 Ga _{1 -z1} As lower cladding layer 2 (0.2 ≦ z1 ≦ 0.8), n− or i on an n-GaAs substrate 1. -GaAs lower optical waveguide layer _{3, In x3 Ga 1-x3} As 1-y3 P y3 compressive strain quantum well active layer (0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1) 4, p- or i-GaAs upper optical guide On the laminated body in which the wave layers 5 are laminated, openings are formed in a stripe shape extending in the direction of the resonator in a current injection region 20 having a width dc and a region having a dc / 2 width separated by db ₁ on both sides of the current injection region 20. A p-In _x8 Ga _{1 -x8} P first etching blocking layer 6 (0 ≦ x8 ≦ 1) and an n-GaAs current confinement layer 7, and on the n-GaAs current confinement layer 7 and other than the current injection region 20. on the p-GaAs upper optical waveguide layer 5 exposed in the _{opening, p-in x9 Ga 1 -x9} P second etching stop layer 8 (0 ≦ x9 ≦ 1), and an n-Al _z1 Ga _{1 -z1} As current confinement layer 9 having an opening in the current injection region 20 is provided on the second etching stop layer 8, and this n-Al _z1 Ga _{1 A} p-Al _z1 Ga _{1 -z1} As upper cladding layer 10 and a p-GaAs contact layer 11 are provided on the _-z1 As current confinement layer 9 and the GaAs upper optical waveguide layer 5 exposed at the opening of the current injection region 20. It will be.
[0025]
In the present embodiment, the composition of the lower cladding layer may be p-In _0.49 Ga _0.51 P lattice-matched with GaAs, and the refractive index distribution necessary for the formation of the ARROW structure is obtained in the same manner.
[0026]
This semiconductor laser device is higher than the equivalent refractive index nc of the core region on both sides of the core region defined by the stripe-shaped current injection region 20 in the direction horizontal to the active layer, due to the layer configuration described above. A high refractive index region having an equivalent refractive index nb, a low refractive index region having an equivalent refractive index nc equivalent to that of the core region on the outside thereof, and a second high refractive index region having an equivalent refractive index nb on the outside thereof. An equivalent refractive index distribution as shown in FIG. 2 is formed.
[0027]
As described above, when the oscillation wavelength is λ, the equivalent refractive index of the core region is nc, and the refractive index of the high refractive index region on both sides of the core region is nb, the width of the high refractive index region on both sides of the core region db ₁
[Equation 3]

It is desirable that Note that m is a positive integer. In addition, the dc / 2-width low-refractive index region provided outside this high-refractive index region suppresses leakage of light output in the lateral direction (direction with an equivalent refractive index distribution), and is a diffraction-limited single peak. It is possible to form a good ARROW structure in which a characteristic oscillation can be obtained.
[0028]
Next explained is a semiconductor laser device according to the second embodiment of the invention. A sectional view of the semiconductor laser element is shown in FIG. In addition, the same code | symbol is attached | subjected to the layer equivalent to 1st Embodiment, and detailed description is abbreviate | omitted (hereinafter the same). The semiconductor laser device of the present embodiment includes an InGaAs quantum well layer 14 having a band gap smaller than that of the quantum well active layer 4 in the middle of the stacking direction of the n-GaAs current confinement layer 7. In the device including the InGaAs quantum well layer 14, light absorption occurs in the InGaAs quantum well layer 14, so that the fundamental transverse mode oscillation gain is increased.
[0029]
Further, the present invention is not limited to the single-core ARROW structure as described above, and may be a structure having a multi-core. In the case of a multi-core ARROW structure, the equivalent refractive index distribution in the direction horizontal to the active layer is as shown in FIG. In this case, the width db ₁ of the high refractive index region arranged at both ends of the plurality of core regions having the width dc satisfies the above formula, and the high refractive index region between the core regions has the width db ₂
[Expression 4]

It is desirable to satisfy. Note that m is a positive integer.
[0030]
Next explained is a semiconductor laser device according to the third embodiment of the invention. A sectional view of the semiconductor laser element is shown in FIG. A cross-sectional view of an element having an ARROW structure having a multi-core as described above is shown. Although this embodiment has the same layer structure as the semiconductor laser device of the first embodiment, it has three current injection regions 21a, 21b, 21c of width dc provided at intervals of width db ₂ and currents at both ends. The p-In _x8 Ga _{1 -x8} P first etching blocking layer 6 and the n-GaAs current confinement layer 7 each having an opening in a dc / 2 width region separated by db ₁ are provided on both sides of the implantation regions 21a and 21c. Is different in that it has three core regions. In this way, higher output can be achieved by using a multi-core.
[0031]
As a method for growing the semiconductor layer, a molecular beam epitaxial growth method using a solid or gas as a raw material may be used. The above structure grows the n-type layer first, but may grow from the p-type layer, in which case it is only necessary to reverse the conductivity.
[0032]
The active layer may have a multiple quantum well structure. Also, a tensile strain i-In _x4 Ga _1-x4 As _1-y4 P _y4 (0 ≦ x4 <0.49y4, 0 <y4 ≦ 0.4) barrier layer that compensates for the compressive strain of the active layer is sandwiched between the active layers. It may be provided. Thereby, the total strain near the active layer can be reduced and the crystallinity of the active layer can be improved.
[0033]
When the thickness of the GaAs upper optical waveguide layer 5 is 100 nm or less, a p-GaAs layer is provided between the n-GaAs current confinement layer 7 and the p-In _x8 Ga _{1 -x8} P first etching blocking layer 6. As a result, current leakage from the n-GaAs current confinement layer 7 can be prevented, and electrical characteristics can be improved.
[0034]
Further, in order to suppress the recombination non-light emission current due to light absorption at the end face during oscillation, higher output can be achieved by removing the p-GaAs contact layer 11 in the vicinity of the resonator end face.
[0035]
【Example】
An example of a specific layer structure of the semiconductor laser element shown in FIG. 1 and a method for manufacturing the same will be described below with reference to FIG. As growth materials, trimethylgallium (TMG), trimethylindium (TMI), trimethylaluminum (TMA), arsine and phosphine are used as raw materials, silane gas is used as an n-type dopant gas, and dimethyl zinc ( DMZ).
[0036]
As shown in FIG. _6A , an n- _{Alz1Ga1 -z1As} lower cladding layer 2, n- or i-GaAs lower optical waveguide is formed on a (001) n-GaAs substrate 1 by metal organic vapor phase epitaxy. layer _{3, i-In x3 Ga 1} -x3 As 1-y3 P y3 compressive strain quantum well active layer 4 (0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1, about 20nm thick 5), p or An i-GaAs upper optical waveguide layer 5, a p-In _x8 Ga _1-x8 P first etching blocking layer 6, and an n-GaAs current confinement layer 7 (0.5 μm) are laminated. Here, if x3 = 0.2 and y3 = 0, the oscillation wavelength is 980 nm, and the oscillation wavelength can be controlled in the range of 900 <λ <1200 (nm) by changing the composition of the active layer. .
[0037]
Next, as shown in FIG. 6B, a stripe-shaped current injection region 20 having a width of 6 μm and a resist pattern in a region having a width of 3 μm are opened on both sides of the current injection region 20 by a photolithographic method, Using the resist as a mask, the n-GaAs current confinement layer 7 was etched with an etching solution of sulfuric acid and hydrogen peroxide. At this time, etching automatically stopped at the p-In _x8 Ga _1-x8 P first etching stop layer 6. Subsequently, the resist was removed, and the p-In _x8 Ga _1-x8 P first etching blocking layer 6 was etched with a hydrochloric acid-based etching solution. At this time, etching automatically stops at the GaAs upper optical waveguide layer 5 and the GaAs upper optical waveguide layer 5 is exposed. Subsequently, the temperature is raised in the As atmosphere, and then the gas is sequentially switched, whereby the p-In _x9 Ga _1-x9 P second layer is formed on the exposed GaAs upper optical waveguide layer 5 and n-GaAs current confinement layer 7. An etching stop layer 8 (0 ≦ x9 ≦ 1) and an n-Al _z1 Ga _{1 -z1} As current confinement layer 9 (thickness 0.5 μm) were grown in this order. The second etching stop layer 8 may be n-In _x9 Ga _1-x9 P.
[0038]
Next, as shown in FIG. 6C, a resist is applied, the resist in the current injection region is removed, and an n-Al _z1 Ga _{1 -z1} resist is masked with an etching solution of sulfuric acid and hydrogen peroxide solution. The As current confinement layer 9 was etched. At this time, the etching automatically stopped at the p-In _x9 Ga _1-x9 P second etching stop layer 8 automatically. After removing the resist, the p-In _x9 Ga _1-x9 P second etching blocking layer 8 was removed with a hydrochloric acid-based etching solution. At this time, the etching automatically stopped at the GaAs upper optical waveguide layer 5, and a current injection region was formed in the stripe region.
[0039]
Next, as shown in FIG. 6D, the temperature is raised in an As atmosphere with the regrowth surface becoming GaAs and AlGaAs, and the p-Al _z1 Ga _{1 -z1} As upper cladding layer 10 and the p-GaAs contact are formed. Layer 11 was formed. Subsequently, after forming the p-side electrode 12, the substrate is polished, the n-side electrode 13 is formed, and the sample is formed by cleaving the sample with a high-reflectance coating on one side and a low-reflection coating on the other. Then, a semiconductor laser device is formed by forming a chip.
[0040]
The n-Al _z1 Ga _{1 -z1} As current confinement layer 9 may be stacked and then the first conductivity type or second conductivity type GaAs cap layer may be stacked. The patterning of the GaAs cap layer can be performed when the n- _{Alz1Ga1 -z1As} current confinement layer 9 is etched.
[0041]
Since the semiconductor laser device of the present invention has high reliability up to high output, it can be applied as a light source in the fields of high-speed information / image processing and communication, measurement, medical care, and printing.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a semiconductor laser device according to a first embodiment of the present invention. FIG. 2 shows an equivalent refractive index distribution in a horizontal direction in an active layer of a semiconductor laser device having a single-core ARROW structure. FIG. 3 is a cross-sectional view showing a semiconductor laser device according to a second embodiment of the present invention. FIG. 4 shows a horizontal equivalent refractive index distribution in an active layer of a semiconductor laser device having an ARROW structure having a multi-core. FIG. 5 is a sectional view showing a semiconductor laser device according to a third embodiment of the present invention. FIG. 6 is a sectional view showing a semiconductor laser device according to an embodiment of the present invention.
1 n-GaAs substrate _{2 n-Al z1 Ga 1 -z1} As lower cladding layer 3 n-or i-GaAs lower optical waveguide layer _{4 In x3 Ga 1-x3 As} 1-y3 P y3 compressive strain quantum well active layer 5 p - or i-GaAs upper optical waveguide layer _{6 p-In x8 Ga 1 -x8} P first etching stop layer 7 n-GaAs current confinement layer _{8 p-In x9 Ga 1-} x9 P second etching stop layer 9 n-Al _z1 Ga _{1 -z1} As current confinement layer
10 p-Al _z1 Ga _{1 -z1} As upper cladding layer
11 p-GaAs contact layer
12 p-side electrode
13 n-side electrode
20 Current injection region

Claims (5)

On the first conductivity type GaAs substrate, a lower clad layer made of first conductivity type In _0.49 Ga _0.51 P or Al _z1 Ga _{1 -z1} As (where 0.2 ≦ z1 ≦ 0.8), first conductivity type or undoped GaAs lower optical waveguide _{layer, in x3 Ga 1-x3 As} 1-y3 P y3 compressive strain quantum well active layer (where, 0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1), the second conductivity type or undoped GaAs upper optical guide On the laminate formed by laminating wave layers in this order,
A second conductivity type In _x8 Ga _1-x8 P first etching blocking layer having an opening in a stripe shape in the resonance direction of the resonator and an opening at a predetermined distance on both sides of the current injection region and the current injection region (however, 0 ≦ x8 ≦ 1) and a first conductivity type GaAs current confinement layer in this order,
On the first conductivity type GaAs current confinement layer and on the upper optical waveguide layer exposed to the opening in a region other than the current injection region, a second conductivity type In _x9 Ga _1-x9 P second An etching stop layer (where 0 ≦ x9 ≦ 1) and a first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer are provided in this order;
A second conductivity type Al _z1 Ga _{1 -z1} As upper cladding layer and a first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer and the upper optical waveguide layer exposed at the opening of the current injection region A semiconductor laser device comprising a two-conductivity type GaAs contact layer. 2. The semiconductor laser device according to claim 1, wherein a GaAs cap layer of a first conductivity type or a second conductivity type is provided on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer. 3. The second conductivity type GaAs layer is provided between the In _x8 Ga _1-x8 P first etching stop layer and the first conductivity type GaAs current confinement layer. Semiconductor laser element. 4. The semiconductor laser device according to claim 1, further comprising an InGaAs quantum well layer having a band gap smaller than that of the active layer in the middle of the stacking direction of the first conductivity type GaAs current confinement layer. On the first conductivity type GaAs substrate, a lower clad layer made of first conductivity type In _0.49 Ga _0.51 P or Al _z1 Ga _{1 -z1} As (where 0.2 ≦ z1 ≦ 0.8), first conductivity type or undoped GaAs lower optical waveguide _{layer, in x3 Ga 1-x3 As} 1-y3 P y3 compressive strain quantum well active layer (where, 0.49y3 <x3 ≦ 0.4,0 ≦ y3 ≦ 0.1), the second conductivity type or undoped GaAs upper optical guide A wave layer, a second conductivity type In _x8 Ga _1-x8 P first etching blocking layer (where 0 ≦ x8 ≦ 1), and a first conductivity type GaAs current confinement layer are laminated in this order,
The first conductivity type GaAs current confinement layer and the second conductivity type In _x8 Ga _1-x8 P first etching stop layer are separated from each other by a current injection region and a region separated by a predetermined distance from both sides of the current injection region. The upper optical waveguide layer is exposed in a striped manner and heated in an As atmosphere, and then regrown on the first conductive type GaAs current confinement layer and the exposed upper optical waveguide layer by regrowth. The In _x9 Ga _1-x9 P second etching blocking layer (where 0 ≦ x9 ≦ 1) and the first conductive type Al _z1 Ga _1-z1 As current confinement layer are stacked in this order. ,
Removing the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer and the In _x9 Ga _{1 -x9} P second etching blocking layer in the current injection region to expose the upper optical waveguide layer;
After raising the temperature in the As atmosphere, the second conductivity type Al _z1 Ga _{1 -z1} As is formed by regrowth on the first conductivity type Al _z1 Ga _{1 -z1} As current confinement layer and the exposed upper optical waveguide layer. An upper clad layer and a second conductivity type GaAs contact layer are laminated in this order.

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