JPH0621576A - Semiconductor laser and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a long life semiconductor laser excellent in characteristics, by forming a special structure between a clad layer and an active layer, and preventing impurities and defect from diffusing into the active layer. CONSTITUTION:A double hetero structure wherein a Ga0.5In0.5P active layer 4 is sandwiched by an N-(Al0.6Ga0.4)0.5In0.5P clad layer 3 and a P-(Al0.6Ga0.4)0.5 In0.5P clad layer 5 is formed on an N-GaAs substrate 1, via an N-GaAs buffer layer 2. A thin film multilayered structure 6 is formed between the Ga0.5In0.5P active layer 4 and the P-(Al0.6Ga0.4)0.5In0.5P clad layer 5. The thin film multilayered structure is formed by alternately laminateing ten P-(Al0.6Ga0.4)0.5 In0.5P layers 15 of 5nm in thickness and 10 (Al0.6Ga0.4)0.5In0.5P layers 16 of 5nm in thickness to which impurities are not added.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、モードの安定性が高
く、信頼性に優れた半導体レーザに関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser having high mode stability and excellent reliability.

【０００２】[0002]

【従来の技術】可視光領域でレーザ発振を生じて発光す
る半導体レーザは、光情報処理用光源や光計測用光源な
どの用途があり、最近その重要性を増している。中で
も、（Ａｌ_xＧａ_1-x）_0.5Ｉｎ_0.5Ｐ系の材料は、良質の
基板であるＧａＡｓに格子整合し、組成ｘを変化させる
ことで波長０．６８μｍから０．５６μｍの範囲でレー
ザ発振を得ることができるため注目されている。半導体
レーザにはダブルヘテロ構造が用いられる。2. Description of the Related Art A semiconductor laser which emits light by causing laser oscillation in a visible light region has applications such as a light source for optical information processing and a light source for optical measurement, and its importance is recently increasing. Among them, the (Al _x Ga _1-x ) _0.5 In _0.5 P-based material is laser-oscillated in the wavelength range of 0.68 μm to 0.56 μm by lattice matching with GaAs which is a good substrate and changing the composition x. Has been attracting attention because you can get. A double hetero structure is used for the semiconductor laser.

【０００３】以下、従来例を用いてダブルヘテロ構造の
横モード制御型の赤色発光の半導体レーザについて説明
する。この半導体レーザは、図８に示すように、ｎ−Ｇ
ａＡｓ基板１上にｎ−ＧａＡｓバッファ層２、ｎ−（Ａ
ｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラッド層１３、Ｇａ_0.5
Ｉｎ_0.5Ｐ活性層４、ｐ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0
.5Ｐクラッド層１４、ｐ−Ｇａ_0.5Ｉｎ_0.5Ｐ層７、ｎ−
ＧａＡｓ電流ブロック層８、ｐ−ＧａＡｓコンタクト層
９が順次形成され、その後ｐ電極１０およびｎ電極１１
が形成される。ｐ型の不純物には亜鉛（Ｚｎ）を、ｎ型
の不純物にはセレン（Ｓｅ）やシリコン（Ｓｉ）を用い
る。Hereinafter, a lateral mode control type red light emitting semiconductor laser having a double hetero structure will be described with reference to a conventional example. This semiconductor laser, as shown in FIG.
n-GaAs buffer layer 2, n- (A
l _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 13, Ga _0.5
In _0.5 P active layer 4, p- (Al _0.7 Ga _0.3 ) _0.5 In _0
.5 P clad layer 14, p-Ga _0.5 In _0.5 P layer 7, n-
A GaAs current blocking layer 8 and a p-GaAs contact layer 9 are sequentially formed, and then a p-electrode 10 and an n-electrode 11 are formed.
Is formed. Zinc (Zn) is used as the p-type impurity, and selenium (Se) or silicon (Si) is used as the n-type impurity.

【０００４】この半導体レーザでは、有機金属気相成長
法（ＭＯＶＰＥ法）や分子線エピタキシー法（ＭＢＥ
法）などの結晶成長技術が用いられる。これらの結晶成
長技術を用いて、ｎ−ＧａＡｓ基板１上にｎ−ＧａＡｓ
バッファ層２、ｎ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐク
ラッド層１３、Ｇａ_0.5Ｉｎ_0.5Ｐ活性層４、ｐ−（Ａｌ
_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラッド層１４およびｐ−Ｇ
ａ_0.5Ｉｎ_0.5Ｐ層７を順次堆積し、次にホトリソグラフ
ィー技術とエッチング技術により、ｐ−Ｇａ_{0. 5}Ｉｎ_0.5
Ｐ層７とｐ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラッド
層１４とを台形状にエッチングしてメサストライプを形
成し、その後ＭＯＶＰＥ法などを用いてｎ−ＧａＡｓ電
流ブロック層８を選択的に堆積し、さらにｐ−ＧａＡｓ
コンタクト層９を堆積する。In this semiconductor laser, metalorganic vapor phase epitaxy (MOVPE method) and molecular beam epitaxy method (MBE) are used.
Method) is used. By using these crystal growth techniques, n-GaAs is formed on the n-GaAs substrate 1.
Buffer layer 2, n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 13, Ga _0.5 In _0.5 P active layer 4, p- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 14 and p-G
sequentially depositing a _0.5 In _0.5 P layer 7, the following photolithographic technique and etching technique, p-Ga _{0. 5} In _0.5
The P layer 7 and the p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 14 are trapezoidally etched to form a mesa stripe, and then the n-GaAs current block layer 8 is selectively formed by using the MOVPE method or the like. Deposited on p-GaAs
The contact layer 9 is deposited.

【０００５】このような半導体レーザの構造では、ｎ−
ＧａＡｓ電流ブロック層８により電流の狭窄を行うこと
ができ、またｐ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラ
ッド層１４を台形上にエッチングする際に、台形の高さ
及び幅を最適化することにより、単一の横モードの条件
を満足する実効的な屈折率差をつけることができ、光を
効果的に台形下部の活性層付近に閉じこめることができ
た。In the structure of such a semiconductor laser, n-
The GaAs current blocking layer 8 can confine the current, and optimizes the height and width of the trapezoid when the p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 14 is etched on the trapezoid. As a result, an effective refractive index difference satisfying the condition of a single transverse mode can be obtained, and light can be effectively confined near the active layer below the trapezoid.

【０００６】[0006]

【発明が解決しようとする課題】ところが、この半導体
レーザの主な構成材料である（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉ
ｎ_0.5Ｐは、材料の性質上、不純物であるＺｎやＳｅが
拡散しやすいという問題点がある。例えば、発振波長が
８３０ｎｍ帯である半導体レーザの主な構成材料である
ＡｌＧａＡｓの拡散速度と比較すると、（Ａｌ_0.7Ｇａ
_0.3）_0.5Ｉｎ_0.5Ｐのそれは１桁大きく、したがって容
易に拡散が起こる。図８に示すような構造では、３回の
結晶成長（ｎ−ＧａＡｓバッファ層２からｐ−Ｇａ_0.5
Ｉｎ_0.5Ｐ層７までを成長させる第１の結晶成長工程
と、ｎ−ＧａＡｓ電流ブロック層８を形成させる第２の
結晶成長工程と、ｐ−ＧａＡｓコンタクト層９を形成さ
せる第３の結晶成長工程）が必要であり、第２および第
３の結晶成長工程の昇温時にＧａ_{0. 5}Ｉｎ_0.5Ｐ活性層４
への不純物であるＺｎやＳｅの異常拡散が生じ易い。そ
れを図９に示す。図９はＳＩＭＳによる図８の半導体レ
ーザの深さ方向の元素分布である。同図からクラッド層
１４のｐ不純物であるＺｎが拡散によって活性層を通っ
てｎクラッド層１３にまで拡散していることがわかる。
その結果、図１０のとおりＧａ_0.5Ｉｎ_0.5Ｐ活性層に抵
抗の低い部分３０と抵抗の高い部分３１が偏在し、電流
の注入にムラが生じてレーザ光のモードの不安定の原因
と成り易い。また、不純物であるＺｎやＳｅの拡散と同
時にＧａ_0.5Ｉｎ_0.5Ｐ活性層４への空孔等の固有欠陥の
拡散が誘起される。固有欠陥はＧａＩｎＰ活性層４中で
深い準位を形成する。深い準位は非発光中心をなり、発
光効率を低下させる。そのために所望の光出力を得るた
めに必要な半導体レーザの駆動電流が大きくなり、半導
体レーザの寿命が短くなる恐れが生じる。However, the main constituent material of this semiconductor laser is (Al _0.7 Ga _0.3 ) _0.5 I.
n _0.5 P has a problem that impurities such as Zn and Se easily diffuse due to the nature of the material. For example, when compared with the diffusion rate of AlGaAs, which is the main constituent material of a semiconductor laser with an oscillation wavelength of 830 nm band, (Al _0.7 Ga
That of _0.3 ) _0.5 In _0.5 P is an order of magnitude larger, so diffusion easily occurs. In the structure as shown in FIG. 8, crystal growth is performed three times (from n-GaAs buffer layer 2 to p-Ga _0.5
A first crystal growth step of growing up to the In _0.5 P layer 7, a second crystal growth step of forming the n-GaAs current blocking layer 8, and a third crystal growth step of forming the p-GaAs contact layer 9. ) is necessary, Ga _{0. 5} in _0.5 P active layer 4 during heating of the second and third crystal growth step
Anomalous diffusion of impurities such as Zn and Se easily occurs. It is shown in FIG. FIG. 9 shows the element distribution in the depth direction of the semiconductor laser of FIG. 8 by SIMS. From the figure, it can be seen that Zn, which is a p-impurity of the clad layer 14, is diffused through the active layer to the n-clad layer 13.
As a result, as shown in FIG. 10, the low-resistance portion 30 and the high-resistance portion 31 are unevenly distributed in the Ga _0.5 In _0.5 P active layer, causing unevenness in current injection, which easily causes instability of the laser light mode. . Further, diffusion of impurities such as Zn and Se is induced at the same time as diffusion of intrinsic defects such as vacancies into the Ga _0.5 In _0.5 P active layer 4. The intrinsic defect forms a deep level in the GaInP active layer 4. The deep level serves as a non-emissive center and reduces the light emission efficiency. Therefore, the driving current of the semiconductor laser required to obtain a desired optical output increases, which may shorten the life of the semiconductor laser.

【０００７】この発明の目的は、レーザ光のモードの安
定性が高く、長寿命の半導体レーザを提供することであ
る。An object of the present invention is to provide a semiconductor laser having a high stability of laser light modes and a long life.

【０００８】[0008]

【課題を解決するための手段】上記課題を解決するため
の手段は以下に示すとおりである。Means for solving the problems Means for solving the above problems are as follows.

【０００９】（１）化合物半導体基板上にダブルヘテロ
構造を有しており、クラッド層と活性層との間に不純物
添加の半導体層と不純物無添加の半導体層から成る薄膜
多層構造を有し、かつ上記不純物無添加の半導体層の膜
厚が多数キャリアの拡散長より薄くなっている半導体レ
ーザ。(1) It has a double hetero structure on a compound semiconductor substrate, and has a thin film multilayer structure composed of an impurity-doped semiconductor layer and an impurity-free semiconductor layer between a clad layer and an active layer. Further, a semiconductor laser in which the film thickness of the impurity-free semiconductor layer is smaller than the diffusion length of majority carriers.

【００１０】（２）クラッド層と活性層との間に不純物
添加の半導体層と不純物無添加の半導体層から成る薄膜
多層構造を有する半導体レーザが複数回の結晶成長を有
し、かつ上記薄膜多層構造を１回目の結晶成長で作製す
る半導体レーザの作製方法。(2) A semiconductor laser having a thin film multilayer structure comprising a semiconductor layer with an impurity added and a semiconductor layer without an impurity between a clad layer and an active layer has a plurality of crystal growths, and the thin film multilayer has A method for manufacturing a semiconductor laser in which a structure is manufactured by first crystal growth.

【００１１】（３）クラッド層と活性層との間に不純物
添加の半導体層と不純物無添加の半導体層から成る薄膜
多層構造を作製した後、不純物添加の半導体層から不純
物無添加の半導体層へ不純物を拡散させることにより、
上記薄膜多層構造の自然超格子の一部が無秩序化した状
態に変化する半導体レーザの作製方法。(3) After forming a thin film multilayer structure including a semiconductor layer with an impurity added and a semiconductor layer without an impurity between the clad layer and the active layer, the semiconductor layer with an impurity added is changed to a semiconductor layer without an impurity added. By diffusing impurities,
A method for manufacturing a semiconductor laser, wherein a part of a natural superlattice having the above-mentioned thin film multilayer structure is changed into a disordered state.

【００１２】[0012]

【作用】上記本発明の半導体レーザによれば、クラッド
層と活性層との間に不純物添加の半導体層と不純物無添
加の半導体層から成る薄膜多層構造を有するため、該ク
ラッド層及び不純物添加の半導体層に添加してある不純
物の拡散は薄膜多層構造中の不純物無添加の半導体層で
止まることから、活性層への不純物や欠陥の拡散を防ぐ
ことができ、不純物や欠陥の拡散による半導体レーザの
特性の劣化を防ぐことができ、信頼性の高いレーザを得
ることができる。薄膜多層構造中の不純物無添加の半導
体層の膜厚が多数キャリアの拡散長より薄くしているた
め、該クラッド層の多数キャリアの活性層への注入を妨
げること無く、良好な特性を得ることができる。According to the above-mentioned semiconductor laser of the present invention, since it has a thin film multi-layered structure composed of an impurity-doped semiconductor layer and an impurity-free semiconductor layer between the clad layer and the active layer, The diffusion of the impurities added to the semiconductor layer is stopped in the semiconductor layer with no impurities added in the thin film multilayer structure, so that the diffusion of impurities and defects into the active layer can be prevented, and the semiconductor laser due to the diffusion of impurities and defects can be prevented. It is possible to prevent the deterioration of the characteristics of, and to obtain a highly reliable laser. Since the film thickness of the impurity-free semiconductor layer in the thin film multilayer structure is smaller than the diffusion length of majority carriers, good characteristics can be obtained without hindering the injection of majority carriers of the cladding layer into the active layer. You can

【００１３】本発明の半導体レーザの作製方法によれ
ば、複数回の結晶成長工程を有する半導体レーザの作製
で、第１の結晶成長工程にクラッド層と活性層との間に
不純物添加の半導体層と不純物無添加の半導体層から成
る薄膜多層構造を作製し、しかる後に２回目以降の結晶
成長を行うことにより、不純物や欠陥の結晶成長中の活
性層への拡散を防止できる。不純物無添加の半導体層の
膜厚を該クラッド層の多数キャリアの拡散長より薄くし
ておけば、不純物添加の半導体層から不純物無添加の半
導体層への該不純物の拡散が少なくても半導体レーザの
特性に問題はない。According to the method of manufacturing a semiconductor laser of the present invention, a semiconductor laser having a plurality of crystal growth steps is manufactured. In the first crystal growth step, a semiconductor layer doped with an impurity is added between the cladding layer and the active layer. By producing a thin film multi-layer structure composed of a semiconductor layer containing no impurities and then performing crystal growth for the second time and thereafter, diffusion of impurities and defects into the active layer during crystal growth can be prevented. If the thickness of the undoped semiconductor layer is made smaller than the diffusion length of majority carriers in the cladding layer, the semiconductor laser can be manufactured even if the diffusion of the impurity from the doped semiconductor layer to the undoped semiconductor layer is small. There is no problem in the characteristics of.

【００１４】また、２回目以降の結晶成長を行う間に、
不純物の拡散が起こり、薄膜多層構造内の自然超格子の
一部が無秩序化した状態に変化し、薄膜多層構造中の半
導体結晶のバンドギャップが大きくなる。この結果、活
性層と薄膜多層構造のバンドギャップ差を大きくするこ
とができ、半導体レーザのしきい値電流の低減、温度安
定性の向上などの特性を向上させることができる。During the second and subsequent crystal growths,
Impurity diffusion occurs, a part of the natural superlattice in the thin film multilayer structure changes to a disordered state, and the band gap of the semiconductor crystal in the thin film multilayer structure increases. As a result, the band gap difference between the active layer and the thin film multilayer structure can be increased, and the characteristics such as the reduction of the threshold current of the semiconductor laser and the improvement of temperature stability can be improved.

【００１５】[0015]

【実施例】以下、この発明の実施例を図面を参照しなが
ら説明する。Embodiments of the present invention will be described below with reference to the drawings.

【００１６】図１にこの発明の一実施例の横モード制御
型の赤色半導体レーザの断面図を示し、図２に図１の半
導体レーザの製造工程を表す工程順断面図を示す。FIG. 1 is a sectional view of a lateral mode control type red semiconductor laser according to one embodiment of the present invention, and FIG. 2 is a sectional view showing the steps of manufacturing the semiconductor laser of FIG.

【００１７】この半導体レーザは、図１（ａ）に示すよ
うに、例えばｎ−ＧａＡｓ基板１上にｎ−ＧａＡｓバッ
ファ層２を介してＧａ_0.5Ｉｎ_0.5Ｐ活性層４をｎ−（Ａ
ｌ_{0. 6}Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層３およびｐ−
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５で挟むダ
ブルヘテロ構造を有している。ｐ−（Ａｌ_0.6Ｇａ_0.4）
_0.5Ｉｎ_0.5Ｐクラッド層５とＧａ_0.5Ｉｎ_0.5Ｐ活性層４
との間には、薄膜多層構造６を有している。薄膜多層構
造６の詳細な構造を図１（ｂ）に示す。薄膜多層構造６
は、５ｎｍのｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１
５と５ｎｍの不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉ
ｎ_0.5Ｐ層１６を交互にそれぞれ１０回積層した構造に
なっている。薄膜多層構造６の活性層に近い第１層目は
５ｎｍの不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5
Ｐ層１６である。これにより、活性層に近接したクラッ
ド層中の欠陥を軽減でき、活性層とクラッド層の界面や
活性層近傍のクラッド層の結晶性を良くすることができ
る。ｐ−（Ａｌ_0.6Ｇａ_0.4）_{0. 5}Ｉｎ_0.5Ｐクラッド層５
および薄膜多層構造６のｐ型不純物にはＺｎ等を、ｎ−
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層３のｎ型不
純物にはＳｅ等を用いる。ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5
Ｉｎ_0.5Ｐクラッド層５の多数キャリアである正孔の拡
散長は数μｍであり、上記不純物無添加の（Ａｌ_0.6Ｇ
ａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６はこの拡散長より充分薄く
しなければならない。もし不純物無添加の（Ａｌ_0.6Ｇ
ａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６が厚く、正孔の拡散長に近
ければ、Ｇａ_0.5Ｉｎ_0.5Ｐ活性層４への正孔の注入が円
滑に行われず、直列抵抗が高くなるなど半導体レーザの
特性の低下につながる。不純物無添加の（Ａｌ_0.6Ｇａ
_0.4）_0.5Ｉｎ_0.5Ｐ層１６は約５ｎｍ程度が良い。ｐ−
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５の上部に
はｐ−Ｇａ_0.5Ｉｎ_0.5Ｐ層７を有し、ｐ−Ｇａ_0.5Ｉｎ
_0.5Ｐ層７およびｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ
クラッド層５の一部は、台形状のメサストライプに加工
されている。台形の両脇はｎ−ＧａＡｓ電流ブロック層
８を堆積してある。さらにｐ−Ｇａ_0.5Ｉｎ_0.5Ｐ層７と
ｎ−ＧａＡｓ電流ブロック層８の上部にはｐ−ＧａＡｓ
コンタクト層９を有している。上記台形は、Ｇａ_0.5Ｉ
ｎ_0.5Ｐ活性層４内に基本横モードが成立するような幅
５μｍにする。ｎ−ＧａＡｓコンタクト層９にはＣｒ／
Ｐｔ／Ａｕなどのｐ電極１０を、ｎ−ＧａＡｓ基板１に
はＡｕ／Ｇｅ／Ｎｉなどのｎ電極１１を堆積してある。This semiconductor laser is shown in FIG.
As shown in FIG.
Ga through the layer 2_0.5In_0.5The P active layer 4 is n- (A
l_{0. 6}Ga_0.4)_0.5In_0.5P clad layer 3 and p-
(Al_0.6Ga_0.4)_0.5In_0.5Sandwiched between P clad layers 5
It has a bull hetero structure. p- (Al_0.6Ga_0.4)
_0.5In_0.5P clad layer 5 and Ga_0.5In_0.5P active layer 4
And a thin film multi-layer structure 6 is provided. Thin film multi-layer structure
The detailed structure of structure 6 is shown in FIG. Thin film multilayer structure 6
Is 5 nm p- (Al_0.6Ga_0.4)_0.5In_0.5P layer 1
5 and 5 nm without impurities (Al_0.6Ga_0.4)_0.5I
n_0.5In a structure in which P layers 16 are alternately laminated 10 times
Has become. The first layer near the active layer of the thin film multilayer structure 6 is
5 nm without impurities (Al_0.6Ga_0.4)_0.5In_0.5
It is the P layer 16. As a result, the cluster near the active layer
Defects in the active layer and the interface between the active layer and the cladding layer
It is possible to improve the crystallinity of the cladding layer near the active layer.
It p- (Al_0.6Ga_0.4)_{0. Five}In_0.5P clad layer 5
And Zn or the like as the p-type impurity of the thin film multilayer structure 6,
(Al_0.6Ga_0.4)_0.5In_0.5The n-type of the P clad layer 3
Se or the like is used as a pure material. p- (Al_0.6Ga_0.4)_0.5
In_0.5Expansion of holes that are majority carriers of the P-clad layer 5
The scattering length is several μm, and the above-mentioned impurity-free (Al_0.6G
a_0.4)_0.5In_0.5The P layer 16 is sufficiently thinner than this diffusion length
Must. If no impurities are added (Al_0.6G
a_0.4)_0.5In_0.5The P layer 16 is thick and close to the diffusion length of holes.
If so, Ga_0.5In_0.5The hole injection into the P active layer 4 is circular.
The series resistance of the semiconductor laser increases
It leads to deterioration of characteristics. No impurities added (Al_0.6Ga
_0.4)_0.5In_0.5The P layer 16 preferably has a thickness of about 5 nm. p-
(Al_0.6Ga_0.4)_0.5In_0.5On top of the P clad layer 5
Is p-Ga_0.5In_0.5P layer 7 having p-Ga_0.5In
_0.5P layer 7 and p- (Al_0.6Ga_0.4)_0.5In_0.5P
A part of the clad layer 5 is processed into a trapezoidal mesa stripe
Has been done. Both sides of the trapezoid are n-GaAs current blocking layers
8 are deposited. Furthermore, p-Ga_0.5In_0.5With P layer 7
On top of the n-GaAs current blocking layer 8 is p-GaAs.
It has a contact layer 9. The trapezoid is Ga_0.5I
n_0.5Width such that the basic transverse mode is established in the P active layer 4
5 μm. The n-GaAs contact layer 9 contains Cr /
The p-electrode 10 such as Pt / Au is formed on the n-GaAs substrate 1.
Has deposited an n-electrode 11 of Au / Ge / Ni or the like.

【００１８】ｎ−ＧａＡｓ電流ブロック層８やｐ−Ｇａ
Ａｓコンタクト層９を作製する時に、高温になるため
に、ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５
及びｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１５から不
純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６へ
ｐ型不純物であるＺｎが一部拡散することがあるが、Ｚ
ｎの拡散が生じた場合でも、拡散は不純物無添加の（Ａ
ｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_{0 .5}Ｐ層１６で止まるために、Ｇ
ａ_0.5Ｉｎ_0.5Ｐ活性層４へＺｎが拡散することはほとん
どないので、半導体レーザの特性には影響がない。なぜ
ならば、不純物であるＺｎ等はｐ−（Ａｌ_0.6Ｇａ_0.4）
_0.5Ｉｎ_0.5Ｐ層中では、空孔等の固有欠陥と対を成して
安定化する。一方、不純物無添加の（Ａｌ_0.6Ｇａ_0.4）
_0.5Ｉｎ_0.5Ｐ層１６には固有欠陥は少なく、不純物や欠
陥の拡散は不純物無添加の（Ａｌ_{0. 6}Ｇａ_0.4）_0.5Ｉｎ
_0.5Ｐ層１６へ多少起こるものの、拡散をＧａ_0.5Ｉｎ
_0.5Ｐ活性層４まで及ぶことを防ぐことができる。もし
不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６
が無ければ、不純物の拡散を防止する物が無いため、Ｇ
ａ _0.5Ｉｎ_0.5Ｐ活性層４へ不純物のみならず、空孔等の
固有欠陥までも導入される。上記不純物無添加の（Ａｌ
_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６は、空孔等の固有欠陥
が少なければ、多少不純物を添加してあっても構わず、
例えばｐ^-−（Ａｌ_{0 .6}Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層でも構
わない。The n-GaAs current blocking layer 8 and p-Ga
Since the temperature becomes high when the As contact layer 9 is formed
, P- (Al_0.6Ga_0.4)_0.5In_0.5P clad layer 5
And p- (Al_0.6Ga_0.4)_0.5In_0.5From the P layer 15
Pure material without additives (Al_0.6Ga_0.4)_0.5In_0.5To P layer 16
Zn, which is a p-type impurity, may partially diffuse, but Z
Even if the diffusion of n occurs, the diffusion does not include impurities (A
l_0.6Ga_0.4)_0.5In_{0 .Five}To stop at the P layer 16, G
a_0.5In_0.5Zn is hardly diffused into the P active layer 4.
Therefore, the characteristics of the semiconductor laser are not affected. why
Then, impurities such as Zn are p- (Al_0.6Ga_0.4)
_0.5In_0.5In the P layer, it forms a pair with intrinsic defects such as holes.
Stabilize. On the other hand, no impurities (Al_0.6Ga_0.4)
_0.5In_0.5The P layer 16 has few intrinsic defects and is free from impurities and defects.
The diffusion of the pits is performed by adding no impurities (Al_{0. 6}Ga_0.4)_0.5In
_0.5Although it occurs to the P layer 16 to some extent, diffusion of Ga_0.5In
_0.5It can be prevented that the P active layer 4 is reached. if
No impurities added (Al_0.6Ga_0.4)_0.5In_0.5P layer 16
Without, there is nothing to prevent the diffusion of impurities.
a _0.5In_0.5Not only impurities but also holes and the like are added to the P active layer 4.
Even intrinsic defects are introduced. The above-mentioned impurities-free (Al
_0.6Ga_0.4)_0.5In_0.5The P layer 16 has a characteristic defect such as a hole.
If the amount is small, you may add some impurities,
For example p^--(Al_{0 .6}Ga_0.4)_0.5In_0.5Even in the P layer
I don't know.

【００１９】Ｚｎなどの不純物がＧａ_0.5Ｉｎ_0.5Ｐ活性
層４に拡散すると以下の２つの問題点が生じる。すなわ
ち、（１）不純物がＧａ_0.5Ｉｎ_0.5Ｐ活性層４に部分的
に拡散するために、図１０に示すように高抵抗の部分３
１と低抵抗の部分３０が生じて活性層へのキャリアの注
入に分布ができ、半導体レーザのモードの不安定化の原
因となる。また、Ｚｎの拡散により不純物のＺｎだけで
なく空孔等の欠陥もＧａ_0.5Ｉｎ_0.5Ｐ活性層４に導入さ
れるため、空孔等の固有欠陥の拡散が誘起される。固有
欠陥はＧａＩｎＰ活性層４中で深い準位を形成する。深
い準位は非発光中心をなり、発光効率を低下させる。そ
のために所望の光出力を得るために必要な半導体レーザ
の駆動電流が大きくなり、半導体レーザの寿命が短くな
り、信頼性に支障を来す。本発明によると、Ｇａ_0.5Ｉ
ｎ_0.5Ｐ活性層４へのＺｎの拡散がほとんどないため、
モードが安定で、かつ長寿命の半導体レーザを得ること
ができる。When impurities such as Zn diffuse into the Ga _0.5 In _0.5 P active layer 4, the following two problems occur. That is, (1) the impurities are partially diffused into the Ga _0.5 In _0.5 P active layer 4, so that as shown in FIG.
1 and a portion 30 having a low resistance are generated, and carriers are distributed to the active layer, which causes destabilization of the mode of the semiconductor laser. Further, due to the diffusion of Zn, not only impurities Zn but also defects such as vacancies are introduced into the Ga _0.5 In _0.5 P active layer 4, so that diffusion of intrinsic defects such as vacancies is induced. The intrinsic defect forms a deep level in the GaInP active layer 4. The deep level serves as a non-emissive center and reduces the light emission efficiency. Therefore, the drive current of the semiconductor laser required to obtain a desired optical output becomes large, the life of the semiconductor laser becomes short, and reliability is impaired. According to the invention, Ga _0.5 I
Since there is almost no diffusion of Zn into the n _0.5 P active layer 4,
A semiconductor laser having a stable mode and a long life can be obtained.

【００２０】上記の構造の半導体レーザに電圧を印加す
ると、ｐ電極１０側から正孔が、ｎ電極１１側から電子
が注入され、Ｇａ_0.5Ｉｎ_0.5Ｐ活性層４内で正孔と電子
の再結合が起こり発光する。発光した光は端面で共振
し、レーザ発振する。ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ
_0.5Ｐクラッド層５の下部には、ｐ−（Ａｌ_0.6Ｇ
ａ_0.4） _0.5Ｉｎ_0.5Ｐ層１５と不純物無添加の（Ａｌ_0.6
Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６から成る薄膜多層構造６
を有するが、不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉ
ｎ_{0 .5}Ｐ層１６は充分薄いため、正孔のＧａ_0.5Ｉｎ_0.5
Ｐ活性層４への注入を妨げることはない。ｐ−Ｇａ_0.5
Ｉｎ_0.5Ｐ層７およびｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0
.5Ｐクラッド層５に形成された台形状のストライプは、
Ｇａ_0.5Ｉｎ_0.5Ｐ活性層４内に基本横モードが成立する
ような幅（５μｍ）にしてあるため、安定な単一横モー
ドの半導体レーザを得ることができる。A voltage is applied to the semiconductor laser having the above structure.
Then, holes are emitted from the p-electrode 10 side and electrons are emitted from the n-electrode 11 side.
Is injected and Ga_0.5In_0.5Holes and electrons in the P active layer 4
Are recombined to emit light. The emitted light resonates at the end face.
Then, laser oscillation occurs. p- (Al_0.6Ga_0.4)_0.5In
_0.5At the bottom of the P clad layer 5, p- (Al_0.6G
a_0.4) _0.5In_0.5P layer 15 and undoped (Al_0.6
Ga_0.4)_0.5In_0.5Thin film multi-layer structure 6 composed of P layer 16
But with no impurities (Al_0.6Ga_0.4)_0.5I
n_{0 .Five}Since the P layer 16 is sufficiently thin, Ga of holes is_0.5In_0.5
It does not hinder the implantation into the P active layer 4. p-Ga_0.5
In_0.5P layer 7 and p- (Al_0.6Ga_0.4)_0.5In_0
.FiveThe trapezoidal stripe formed on the P clad layer 5 is
Ga_0.5In_0.5Basic transverse mode is established in the P active layer 4.
The width (5 μm) is such that a stable single lateral mode
It is possible to obtain a semiconductor laser.

【００２１】つぎに、この半導体レーザの作製方法を図
２を参照しながら説明する。まず、ＭＯＶＰＥ法などの
結晶成長方法を用いて、ｎ−ＧａＡｓ基板１の上にｎ−
ＧａＡｓバッファ層２、ｎ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉ
ｎ_0.5Ｐクラッド層３、Ｇａ_{0. 5}Ｉｎ_0.5Ｐ活性層４、５
ｎｍのｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１５と５
ｎｍの不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ
層１６を１周期とする薄膜多層構造６、ｐ−（Ａｌ_0.6
Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５、ｐ−Ｇａ_{0. 5}Ｉｎ
_0.5Ｐ層７をエピタキシャル成長する（（ａ）図）。薄
膜多層構造６の活性層に近い第１層目は不純物無添加の
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６である。この薄
膜多層構造６は１０周期から成る。ホトリソグラフィー
技術とエッチング技術を用いて、ＳｉＯ₂１２とｐ−Ｇ
ａ_0.5Ｉｎ_0.5Ｐ層７とｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ
_0.5Ｐクラッド層５の一部を台形状のストライプに加工
する（（ｂ）図）。台形状に加工した後、ＭＯＶＰＥ法
の選択成長技術を用いて、ｎ−ＧａＡｓ電流ブロック層
８をＳｉＯ₂１２上に堆積させることなく、台形の両脇
に結晶成長させる（（ｃ）図）。その後、ＳｉＯ₂１２
を除去し、ｐ−ＧａＡｓコンタクト層９を結晶成長させ
る（（ｄ）図）。ｎ−ＧａＡｓ電流ブロック層８若しく
はｐ−ＧａＡｓコンタクト層９を結晶成長する時に高温
状態になるために、ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5
Ｐクラッド層５及びｐ−（Ａｌ_0.6Ｇａ_0.4） _0.5Ｉｎ_0.5
Ｐ層１５から不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉ
ｎ_0.5Ｐ層１６へｐ型不純物であるＺｎが一部拡散する
ことがあるが、拡散は不純物無添加の（Ａｌ_0.6Ｇ
ａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６で止まるため、Ｇａ_0.5Ｉｎ
_0.5Ｐ活性層４へＺｎが拡散することはほとんどない。
不純物であるＺｎはｐ−（Ａｌ_0.6Ｇａ_{0 .4}）_0.5Ｉｎ_0.5
Ｐ層中では、空孔等の固有欠陥と対を成して安定化す
る。一方、不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ
_0.5Ｐ層１６には固有欠陥は少なく、不純物の拡散は不
純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６へ
多少起こるものの、拡散をＧａ_0.5Ｉｎ_0.5Ｐ活性層４ま
で及ぶことを防ぐことができる。もし不純物無添加の
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６が無ければ、不
純物の拡散を防止する層が無いため、Ｇａ_0.5Ｉｎ_0.5Ｐ
活性層４へ不純物のみならず、空孔等の固有欠陥までも
導入される。ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１
５と不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層
１６から成る薄膜多層構造６を設けることで、Ｇａ_0.5
Ｉｎ_0.5Ｐ活性層４へ欠陥の導入を防ぐことができる。Next, a method of manufacturing this semiconductor laser will be described.
This will be described with reference to 2. First of all, such as MOVPE method
By using the crystal growth method, n- is formed on the n-GaAs substrate 1.
GaAs buffer layer 2, n- (Al_0.6Ga_0.4)_0.5I
n_0.5P clad layer 3, Ga_{0. Five}In_0.5P active layers 4, 5
nm p- (Al_0.6Ga_0.4)_0.5In_0.5P layers 15 and 5
nm without impurities (Al_0.6Ga_0.4)_0.5In_0.5P
Thin film multi-layer structure 6, p- (Al_0.6
Ga_0.4)_0.5In_0.5P clad layer 5, p-Ga_{0. Five}In
_0.5The P layer 7 is epitaxially grown (Fig. (A)). Thin
The first layer, which is close to the active layer of the film multilayer structure 6, has no impurities added.
(Al_0.6Ga_0.4)_0.5In_0.5It is the P layer 16. This thin
The film multilayer structure 6 has 10 periods. Photolithography
Technology and etching technology₂12 and p-G
a_0.5In_0.5P layer 7 and p- (Al_0.6Ga_0.4)_0.5In
_0.5Part of the P-clad layer 5 is processed into a trapezoidal stripe
(Figure (b)). MOVPE method after processing into trapezoid
N-GaAs current blocking layer using the selective growth technique of
8 for SiO₂12 sides of trapezoid without depositing on 12
Crystal growth is performed (Fig. (C)). After that, SiO₂12
Are removed, and the p-GaAs contact layer 9 is crystal-grown.
(Fig. (D)). n-GaAs current blocking layer 8
Is high temperature during crystal growth of the p-GaAs contact layer 9.
P- (Al_0.6Ga_0.4)_0.5In_0.5
P clad layer 5 and p- (Al_0.6Ga_0.4) _0.5In_0.5
No impurities are added from the P layer 15 (Al_0.6Ga_0.4)_0.5I
n_0.5Zn, which is a p-type impurity, partially diffuses into the P layer 16.
In some cases, diffusion does not include impurities (Al_0.6G
a_0.4)_0.5In_0.5Since it stops at the P layer 16, Ga_0.5In
_0.5Zn hardly diffuses into the P active layer 4.
The impurity Zn is p- (Al_0.6Ga_{0 .Four})_0.5In_0.5
In the P layer, it stabilizes by pairing with intrinsic defects such as holes.
It On the other hand, no impurities (Al_0.6Ga_0.4)_0.5In
_0.5The P layer 16 has few intrinsic defects and diffusion of impurities is not
Pure material without additives (Al_0.6Ga_0.4)_0.5In_0.5To P layer 16
Although it occurs to some extent, diffusion is Ga_0.5In_0.5P active layer 4
Can be prevented from reaching. If no impurities are added
(Al_0.6Ga_0.4)_0.5In_0.5Without the P layer 16,
Since there is no layer that prevents the diffusion of pure substances, Ga_0.5In_0.5P
Not only impurities in the active layer 4 but also intrinsic defects such as vacancies
be introduced. p- (Al_0.6Ga_0.4)_0.5In_0.5P layer 1
5 with no impurities (Al_0.6Ga_0.4)_0.5In_0.5P layer
By providing a thin film multilayer structure 6 made of_0.5
In_0.5It is possible to prevent the introduction of defects into the P active layer 4.

【００２２】上記不純物無添加の（Ａｌ_0.6Ｇａ_0.4）
_0.5Ｉｎ_0.5Ｐ層１６は、空孔等の固有欠陥が少なけれ
ば、多少不純物を添加してあっても構わず、例えばｐ^-
−（Ａｌ_{0 .6}Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層でも構わない。The above-mentioned impurity-free (Al _0.6 Ga _0.4 )
_{The 0.5} In _0.5 P layer 16 may be added with some impurities as long as it has few intrinsic defects such as vacancies. For example, p ^{− −}
- (Al _{0 .6} Ga _0.4) may be _0.5 an In _0.5 P layer.

【００２３】最後にｐ−ＧａＡｓコンタクト層９上にＣ
ｒ／Ｐｔ／Ａｕを堆積してｐ電極１０とし、ｎ−ＧａＡ
ｓ基板１上にＡｕ／Ｇｅ／Ｎｉを堆積してｎ電極１１と
する（（ｅ）図）。Finally, C is formed on the p-GaAs contact layer 9.
n / GaA was formed by depositing r / Pt / Au to form the p-electrode 10.
Au / Ge / Ni is deposited on the s substrate 1 to form the n-electrode 11 ((e) diagram).

【００２４】このような製造方法により、図１に示すよ
うな横モード制御型の赤色半導体レーザを作製すること
ができる。With such a manufacturing method, a lateral mode control type red semiconductor laser as shown in FIG. 1 can be manufactured.

【００２５】（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5ＰはＭＯＶ
ＰＥ法等で結晶成長すると、III族元素であるＡｌとＧ
ａとＩｎが規則正しく並ぶ自然超格子を形成しやすい。
この自然超格子を形成すると、（Ａｌ_0.6Ｇａ_0.4）_0.5
Ｉｎ_0.5Ｐ結晶のバンドギャップが小さくなる。自然超
格子を形成した状態と形成しない状態では、バンドギャ
ップが約７０ｍｅＶ異なる。１回目の結晶成長で、ｎ−
ＧａＡｓ基板１の上にｎ−ＧａＡｓバッファ層２、ｎ−
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層３、Ｇａ
_0.5Ｉｎ_0.5Ｐ活性層４、５ｎｍのｐ−（Ａｌ_0.6Ｇ
ａ_0.4）_0.5Ｉｎ_0.5Ｐ層１５と５ｎｍの不純物無添加の
（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６から成る薄膜多
層構造６、ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッ
ド層５、ｐ−Ｇａ_{0. 5}Ｉｎ_0.5Ｐ層７をエピタキシャル成
長する。２回目以降の結晶成長で、ｐ−（Ａｌ_0.6Ｇａ
_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５及びｐ−（Ａｌ_0.6Ｇａ
_0.4）_0.5Ｉｎ_{0 .5}Ｐ層１５から不純物無添加の（Ａｌ_0.6
Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１６へｐ型不純物であるＺｎ
等の拡散が起こる。この時の不純物の拡散により薄膜多
層構造６内の自然超格子の一部が無秩序化した状態に変
化し、薄膜多層構造６中の（Ａｌ _0.6Ｇａ_0.4）_0.5Ｉｎ
_0.5Ｐ結晶のバンドギャップが大きくなる。それを図７
に示す。この結果、Ｇａ_0.5Ｉｎ_0.5Ｐ活性層４と薄膜多
層構造６のバンドギャップ差を大きくすることができ、
活性層４内にキャリアが閉じこめられやすくなり、半導
体レーザのしきい値電流の低減、温度安定性の向上など
の特性を向上させることができる。(Al_0.6Ga_0.4)_0.5In_0.5P is MOV
When the crystal is grown by the PE method or the like, the group III elements Al and G
It is easy to form a natural superlattice in which a and In are regularly arranged.
When this natural superlattice is formed, (Al_0.6Ga_0.4)_0.5
In_0.5The band gap of the P crystal becomes small. Supernatural
With the grid formed and not formed, the band gap is
The difference is about 70 meV. In the first crystal growth, n-
N-GaAs buffer layer 2, n- on the GaAs substrate 1
(Al_0.6Ga_0.4)_0.5In_0.5P clad layer 3, Ga
_0.5In_0.5P active layer 4, 5 nm p- (Al_0.6G
a_0.4)_0.5In_0.5P layer 15 and 5 nm impurity-free
(Al_0.6Ga_0.4)_0.5In_0.5Many thin films composed of P layer 16
Layer structure 6, p- (Al_0.6Ga_0.4)_0.5In_0.5P crush
Layer 5, p-Ga_{0. Five}In_0.5Epitaxial formation of P layer 7
Lengthen. In the second and subsequent crystal growth, p- (Al_0.6Ga
_0.4)_0.5In_0.5P clad layer 5 and p- (Al_0.6Ga
_0.4)_0.5In_{0 .Five}No impurities are added from the P layer 15 (Al_0.6
Ga_0.4)_0.5In_0.5Zn, which is a p-type impurity, is added to the P layer 16.
And so on. Due to diffusion of impurities at this time, many thin films
A part of the natural superlattice in the layer structure 6 changes to a disordered state.
In the thin film multilayer structure 6 (Al _0.6Ga_0.4)_0.5In
_0.5The band gap of the P crystal becomes large. Figure 7
Shown in. As a result, Ga_0.5In_0.5P active layer 4 and thin film
The band gap difference of the layer structure 6 can be increased,
Carriers are easily trapped in the active layer 4 and
Body laser threshold current reduction, temperature stability improvement, etc.
The characteristics of can be improved.

【００２６】本実施例では、（Ａｌ_xＧａ_1-x）_0.5Ｉｎ
_0.5Ｐ（０≦ｘ≦１）中で拡散しやすい不純物としてＺ
ｎを用いて説明した。しかし、その他の不純物、例えば
Ｓｅ等の場合でも不純物添加の半導体層と不純物無添加
の半導体層から成る薄膜多層構造をクラッド層と活性層
の間に形成することにより、モードが安定で、信頼性の
高い、良好な特性の半導体レーザを作製するこができ
る。In this embodiment, (Al _x Ga _1-x ) _0.5 In
Z as an impurity that easily diffuses in _0.5 P (0 ≦ x ≦ 1)
It explained using n. However, even in the case of other impurities such as Se, the mode is stable and the reliability is improved by forming a thin film multilayer structure including a semiconductor layer with an impurity and a semiconductor layer without an impurity between the cladding layer and the active layer. It is possible to manufacture a semiconductor laser having high characteristics and good characteristics.

【００２７】なお、本実施例では、薄膜多層構造６をＧ
ａ_0.5Ｉｎ_0.5Ｐ活性層４とｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5
Ｉｎ_0.5Ｐクラッド層５の間に配置したが、ｐ−（Ａｌ
_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層５全体を薄膜多層
構造６と同様の構造にすれば、ｐ型不純物の拡散をより
防止できる。また、実施例中では薄膜多層構造６を５ｎ
ｍのｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層１５と５ｎ
ｍの不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層
１６を１周期とする周期的な構造としているが、薄膜多
層構造６内の不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉ
ｎ_0.5Ｐ層が多数キャリアの拡散長よりも薄ければ、周
期的な構造にする必要はなく、この発明の効果は大き
い。In the present embodiment, the thin film multilayer structure 6 is
a _0.5 In _0.5 P active layer 4 and p- (Al _0.6 Ga _0.4 ) _0.5
It was arranged between the In _0.5 P clad layers 5, but p- (Al
_{If the} entire _0.6 Ga _0.4 ) _0.5 In _0.5 P cladding layer 5 has a structure similar to the thin film multilayer structure 6, diffusion of p-type impurities can be prevented more effectively. In addition, in the embodiment, the thin film multilayer structure 6 has a thickness of 5n.
m p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P layer 15 and 5n
Although the impurity-free (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P layer 16 of m has a periodic structure, the non-doped (Al _0.6 Ga _0.4 ) _0.5 I in the thin-film multilayer structure 6 has a periodic structure.
If the n _0.5 P layer is thinner than the diffusion length of majority carriers, it is not necessary to have a periodic structure, and the effect of the present invention is great.

【００２８】上記実施例では、ダブルヘテロ構造を構成
する材料を指定したが、クラッド層が（Ａｌ_yＧａ_1-y）
_0.5Ｉｎ_0.5Ｐ、活性層が（Ａｌ_zＧａ_1-z）_0.5Ｉｎ_0.5Ｐ
（ここで、０≦ｚ≦ｙ≦１）の場合でも、モードが安定
で、信頼性の高い、良好な特性の半導体レーザを作製す
ることができる。また、薄膜多層構造６を構成する不純
物添加の半導体層と不純物無添加の半導体層の材料を同
一にしたが、この２つの半導体層の材料が異なってもよ
い。不純物添加の半導体層と不純物無添加の半導体層の
Ａｌの割合（組成）を変えても良く、例えば、不純物添
加の半導体層にｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層
を、不純物無添加の半導体層に不純物無添加の（Ａｌ
_0.15Ｇａ_0.85）_0.5Ｉｎ_0.5Ｐ層を用いても、この発明の
効果は大きい。[0028] In the above embodiment, specifying the material constituting the double hetero structure, the cladding layer is (Al _y Ga _1-y)
0.5 In _0.5 P, active layer is (Al _z Ga _1-z ) _0.5 In _0.5 P
Even in the case of (where 0 ≦ z ≦ y ≦ 1), it is possible to manufacture a semiconductor laser with stable characteristics, high reliability, and good characteristics. Further, although the material of the impurity-added semiconductor layer and the material of the impurity-free semiconductor layer forming the thin-film multilayer structure 6 are the same, the materials of the two semiconductor layers may be different. The ratio (composition) of Al in the impurity-added semiconductor layer and the impurity-undoped semiconductor layer may be changed. For example, a p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P layer may be added to the impurity-added semiconductor layer and an impurity-free semiconductor layer may be added. No impurity is added to the added semiconductor layer (Al
_{Even if a 0.15} Ga _0.85 ) _0.5 In _0.5 P layer is used, the effect of the present invention is great.

【００２９】[0029]

【発明の効果】本発明の半導体レーザによれば、 （１）ダブルヘテロ構造を有する半導体レーザにおい
て、クラッド層と活性層との間に不純物添加の半導体層
と不純物無添加の半導体層から成る薄膜多層構造を有
し、不純物無添加の半導体層が多数キャリアの拡散長よ
り充分薄いので、キャリアの活性層への注入を妨げるこ
となく、活性層への不純物や欠陥の拡散を防止でき、モ
ードが安定で、かつ長寿命の半導体レーザを得ることが
できる。 （２）薄膜多層構造の活性層に近い第１層目が不純物無
添加の半導体層とすることで、活性層に近接したクラッ
ド層中の欠陥を少なくでき、活性層とクラッド層の界面
や活性層近傍のクラッド層の結晶性を良くするこがで
き、また不純物と欠陥の活性層への導入を軽減できる。According to the semiconductor laser of the present invention, (1) in a semiconductor laser having a double hetero structure, a thin film composed of an impurity-doped semiconductor layer and an impurity-undoped semiconductor layer between a clad layer and an active layer. Since it has a multilayer structure and the impurity-free semiconductor layer is sufficiently thinner than the diffusion length of majority carriers, it is possible to prevent the diffusion of impurities and defects into the active layer without hindering the injection of carriers into the active layer. It is possible to obtain a stable and long-life semiconductor laser. (2) Since the first layer near the active layer of the thin film multilayer structure is a semiconductor layer containing no impurities, defects in the clad layer adjacent to the active layer can be reduced, and the interface between the active layer and the clad layer and the active layer can be reduced. The crystallinity of the clad layer near the layer can be improved, and the introduction of impurities and defects into the active layer can be reduced.

【００３０】本発明の半導体レーザの作製方法によれ
ば、 （３）クラッド層と活性層の間に不純物添加の半導体層
と不純物無添加の半導体層から成る薄膜多層構造を有す
る半導体レーザが複数回の結晶成長を有し、かつ上記薄
膜多層構造を１回目の結晶成長で作製することにより、
不純物や欠陥の結晶成長中の活性層への拡散を防止で
き、モードが安定で、信頼性に優れた半導体レーザを作
製することができる。According to the method of manufacturing a semiconductor laser of the present invention, (3) a semiconductor laser having a thin film multilayer structure including a semiconductor layer with an impurity added and a semiconductor layer without an impurity between a cladding layer and an active layer is provided a plurality of times. And has the above-mentioned thin film multilayer structure produced by the first crystal growth,
Diffusion of impurities and defects into the active layer during crystal growth can be prevented, and a semiconductor laser having a stable mode and excellent reliability can be manufactured.

【００３１】（４）複数回の結晶成長を有する半導体レ
ーザの作製方法において、１回目の結晶成長でクラッド
層と活性層との間に不純物添加の半導体層と不純物無添
加の半導体層からなる薄膜多層構造を作製し、２回目以
降の結晶成長で不純物添加の半導体層から不純物無添加
の半導体層へ不純物が拡散するが、不純物無添加の半導
体層で拡散を停止させることで、活性層への不純物や欠
陥の拡散を防ぐことができる。(4) In the method of manufacturing a semiconductor laser having a plurality of crystal growths, a thin film composed of an impurity-doped semiconductor layer and an impurity-free semiconductor layer between the cladding layer and the active layer in the first crystal growth. Impurities diffuse from the impurity-added semiconductor layer to the impurity-undoped semiconductor layer in the second and subsequent crystal growths by forming a multilayer structure, but by stopping the diffusion in the impurity-free semiconductor layer, It is possible to prevent the diffusion of impurities and defects.

【００３２】また本発明の他の半導体レーザの作製方法
によれば、 （５）クラッド層と活性層との間に不純物添加の半導体
層と不純物無添加の半導体層から成る薄膜多層構造を作
製した後、不純物添加の半導体層から不純物無添加の半
導体層へ不純物を拡散させることにより、上記薄膜多層
構造の自然超格子の一部が無秩序化した状態に変化する
ことで、活性層と薄膜多層構造のバンドギャップ差を大
きくすることができ、半導体レーザのしきい値電流の低
減、温度安定性の向上などの特性を向上させることがで
きる。According to another method of manufacturing a semiconductor laser of the present invention, (5) a thin film multilayer structure including a semiconductor layer with an impurity added and a semiconductor layer without an impurity between the clad layer and the active layer is manufactured. Then, by diffusing the impurities from the doped semiconductor layer to the undoped semiconductor layer, a part of the natural superlattice of the thin film multilayer structure is changed into a disordered state, and the active layer and the thin film multilayer structure are changed. The band gap difference can be increased, and the characteristics such as the reduction of the threshold current and the temperature stability of the semiconductor laser can be improved.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の実施例の横モード制御型の赤色半導体
レーザの断面図である。FIG. 1 is a cross-sectional view of a lateral mode control type red semiconductor laser according to an embodiment of the present invention.

【図２】本発明の半導体レーザの製造工程を表す第１の
工程順断面図である。FIG. 2 is a first process step cross-sectional view showing a manufacturing process of a semiconductor laser of the present invention.

【図３】本発明の半導体レーザの製造工程を表す第２の
工程順断面図である。FIG. 3 is a second process step cross-sectional view showing a manufacturing process of the semiconductor laser of the present invention.

【図４】本発明の半導体レーザの製造工程を表す第３の
工程順断面図である。FIG. 4 is a third process step cross-sectional view showing a process for manufacturing a semiconductor laser of the present invention.

【図５】本発明の半導体レーザの製造工程を表す第４の
工程順断面図である。FIG. 5 is a fourth process step cross-sectional view illustrating a process for manufacturing a semiconductor laser of the present invention.

【図６】本発明の半導体レーザの製造工程を表す第５の
工程順断面図である。FIG. 6 is a fifth process step cross-sectional view illustrating a process for manufacturing a semiconductor laser of the present invention.

【図７】薄膜多層構造を無秩序化する前後でのエネルギ
ーバンド図である。FIG. 7 is an energy band diagram before and after disordering a thin film multilayer structure.

【図８】赤色半導体レーザの構成断面図である。FIG. 8 is a cross-sectional view of a structure of a red semiconductor laser.

【図９】ＳＩＭＳによるＰ型不純物Ｚｎの拡散を説明す
るための図である。FIG. 9 is a diagram for explaining diffusion of P-type impurity Zn by SIMS.

【図１０】Ｐ型不純物Ｚｎの拡散により活性層にできた
抵抗の分布を示す図である。FIG. 10 is a diagram showing a distribution of resistance formed in an active layer by diffusion of P-type impurity Zn.

【符号の説明】[Explanation of symbols]

１ ｎ−ＧａＡｓ基板 ２ ｎ−ＧａＡｓバッファ層 ３ ｎ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層 ４ Ｇａ_0.5Ｉｎ_0.5Ｐ活性層 ５ ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐクラッド層 ６ 薄膜多層構造 ７ ｐ−Ｇａ_0.5Ｉｎ_0.5Ｐ層 ８ ｎ−ＧａＡｓ電流ブロック層 ９ ｐ−ＧａＡｓコンタクト層 １０ ｐ電極 １１ ｎ電極 １２ ＳｉＯ₂ １３ ｎ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラッド層 １４ ｐ−（Ａｌ_0.7Ｇａ_0.3）_0.5Ｉｎ_0.5Ｐクラッド層 １５ ｐ−（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ層 １６ 不純物無添加の（Ａｌ_0.6Ｇａ_0.4）_0.5Ｉｎ_0.5Ｐ
層1 n-GaAs substrate 2 n-GaAs buffer layer 3 n- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad layer 4 Ga _0.5 In _0.5 P active layer 5 p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P clad layer 6 Thin film multilayer structure 7 p-Ga _0.5 In _0.5 P layer 8 n-GaAs current blocking layer 9 p-GaAs contact layer 10 p electrode 11 n electrode 12 SiO ₂ 13 n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 14 p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 15 p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P layer 16 (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P without impurities
layer

Claims (5)

【特許請求の範囲】[Claims] 【請求項１】 ダブルヘテロ構造を有する半導体レーザ
において、クラッド層と活性層との間に不純物添加の半
導体層と不純物無添加の半導体層から成る薄膜多層構造
を有し、かつ上記不純物無添加の半導体層の膜厚が多数
キャリアの拡散長より薄いことを特徴とする半導体レー
ザ。1. A semiconductor laser having a double hetero structure, which has a thin film multilayer structure including a semiconductor layer with an impurity added and a semiconductor layer without an impurity between a clad layer and an active layer, and the above-mentioned impurity-free semiconductor layer. A semiconductor laser characterized in that the film thickness of the semiconductor layer is thinner than the diffusion length of majority carriers. 【請求項２】 薄膜多層構造の活性層側の第１層目が不
純物無添加の半導体層であることを特徴とする請求項１
に記載の半導体レーザ。2. The first layer on the active layer side of the thin film multilayer structure is a semiconductor layer containing no impurities.
The semiconductor laser described in 1. 【請求項３】 クラッド層と活性層との間に不純物添加
の半導体層と不純物無添加の半導体層から成る薄膜多層
構造を有する半導体レーザが複数回の結晶成長を有し、
かつ上記薄膜多層構造を１回目の結晶成長で作製するこ
とを特徴とする半導体レーザの作製方法。3. A semiconductor laser having a thin-film multi-layered structure including a semiconductor layer with an impurity added and a semiconductor layer without an impurity between a clad layer and an active layer has a plurality of crystal growths.
A method of manufacturing a semiconductor laser, characterized in that the thin film multilayer structure is manufactured by crystal growth for the first time. 【請求項４】 複数回の結晶成長を有する半導体レーザ
の作製方法において、１回目の結晶成長でクラッド層と
活性層との間に不純物添加の半導体層と不純物無添加の
半導体層から成る薄膜多層構造を作製し、２回目以降の
結晶成長で不純物添加の半導体層から不純物無添加の半
導体層へ不純物が拡散することを特徴とする半導体レー
ザの作製方法。4. A method of manufacturing a semiconductor laser having a plurality of crystal growths, wherein a thin film multilayer including a semiconductor layer with an impurity and a semiconductor layer without an impurity between a cladding layer and an active layer in the first crystal growth. A method for manufacturing a semiconductor laser, wherein a structure is manufactured, and impurities are diffused from a semiconductor layer to which impurities are added to a semiconductor layer to which impurities are not added in a second or subsequent crystal growth. 【請求項５】 クラッド層と活性層との間に不純物添加
の半導体層と不純物無添加の半導体層から成る薄膜多層
構造を作製した後、不純物添加の半導体層から不純物無
添加の半導体層へ不純物を拡散させることにより、上記
薄膜多層構造の自然超格子の一部が無秩序化した状態に
変化することを特徴とする半導体レーザの作製方法。5. A thin film multi-layer structure comprising a semiconductor layer with an impurity added and a semiconductor layer without an impurity between the clad layer and the active layer is manufactured, and then the semiconductor layer without an impurity is added to the semiconductor layer without an impurity. A method of manufacturing a semiconductor laser, characterized in that a part of the natural superlattice of the above-mentioned thin film multilayer structure is changed into a disordered state by diffusing.