JPH01166588A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To improve heat radiation efficiency at a semiconductor laser edge side and to prevent heat generation due to optical absorption at the edge side by forming ZnxSe1-x(0<x<1) of a high resistivity on the semiconductor laser edge side. CONSTITUTION:An n-Ga1-xAlxAs clad layer 2, an n-Ga1-yAlyAs active layer 3, a p-Ga1-xAlxAs clad layer 4, and an n-GaAs cap layer 5 are caused to grow successively on an n-type GaAs substrate 1 of a semiconductor laser. Striped diffusion holes of a desired width are formed on the layer 5 at a desired pitch through photolithography process in the <01-1> direction. Then Zn is diffused in the diffusion holes and a current path which reaches the layer 4 through the layer 5 is formed on a trapezoid groove. Then p side and n side electrodes 6, 7 are formed and a laser chip having a desired length of a resonator is constituted. The chip is put in low pressure MOCVD equipment then a ZnSSE film 8 of a desired thickness which is relevant to half of the laser oscillation wavelength is formed on both the end sides of the resonator of the chip at a predetermined temperature, thus increasing the heat radiation effect of the edge side.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は半導体レーザに係り１％に高出力動作に適した
高信頼のＧａＡｔＡｓ系及びＩｎＧａＡｔＰ系半導体レ
ーザの端面透明化構造に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to semiconductor lasers, and relates to a highly reliable end face transparent structure of GaAtAs and InGaAtP semiconductor lasers suitable for 1% high output operation.

〔従来の技術〕[Conventional technology]

情報端末応用を中心に半導体レーザの高出力化の研究が
活発化している。しかし、高出力化に伴なって、レーザ
共振器内の光子密度が増大し、端面近傍での光吸収によ
る発熱を主原因とする素子劣化が生じ、高出力化の障害
となっていた。解決法としては、レーザ端面近傍の禁制
帯巾を広げる方法が有効で、具体的方法として従来は、
１）端面近傍を除く活性層に不純物を導入する。２）端
面近傍を禁制帯幅の広い材料で埋込む、３）端面近傍の
浩性層厚を薄くする。４）活性層を量子井戸構造として
、不純物導入により端面近傍のみを液晶化して禁制帯幅
を広げる等の方法が取られていた。−族 方、ｎ−ｖｔ洪合物であるＺｎ５ｅは、第３４回応用物
理学会講演予稿集第３分冊、２８ｐ−ＺＨ−８及び９．
Ｐ７１５　（１９８７）に記載されたごとく、格子定数
がＱａＡｓに近く、高抵抗で、屈折率が２５程度とＱ　
ａ　Ａｓと空気の中間に位置する点を利用して、ＧａＡ
ｔＡｓ系レーザの屈折率導波の為の埋込み層として利用
されていた。Research on increasing the output power of semiconductor lasers is intensifying, mainly for information terminal applications. However, with the increase in output power, the photon density within the laser resonator increases, causing device deterioration mainly due to heat generation due to light absorption near the end facets, which has been an obstacle to increasing output power. An effective solution is to widen the forbidden band near the laser end face.
1) Impurities are introduced into the active layer except for the vicinity of the end face. 2) Filling the vicinity of the end face with a material with a wide forbidden band width; 3) Reducing the thickness of the bulk layer near the end face. 4) A method has been used in which the active layer is made into a quantum well structure and only the vicinity of the end face is made liquid crystal by introducing impurities to widen the forbidden band width. Zn5e, which is an n-vt complex, is described in Proceedings of the 34th Japan Society of Applied Physics, Volume 3, 28p-ZH-8 and 9.
P715 (1987), the lattice constant is close to that of QaAs, the resistance is high, and the refractive index is about 25.
a Using the point located between As and air, GaA
It was used as a buried layer for refractive index waveguide of tAs-based lasers.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

上記端面近傍の県制帯巾を広げる従来技術は素子作製時
における再現性の点に問題がめった。本発明の目的は作
製°が容易で、かつ再現性の良い高出力高信頼レーザを
提供することにある。The conventional technique of widening the prefectural band width near the end faces has encountered problems in terms of reproducibility during device fabrication. An object of the present invention is to provide a high-output, highly reliable laser that is easy to manufacture and has good reproducibility.

〔問題点を解決するための手段〕[Means for solving problems]

上記目的は、半導体レーザ端面に高抵抗のＺｎＳｍ５ｅ
ｌ−ｘ膜（０＜、Ｘく１）を３００Ｃ前後の低温におい
て形成することにより達成される。The above purpose is to add high resistance ZnSm5e to the semiconductor laser end face.
This is achieved by forming an l-x film (0<, X x 1) at a low temperature of around 300C.

〔作用〕[Effect]

Ｚ　ｎ　Ｓ　ｚ　Ｓ　ｅ　ｔ　−ｍ　ＰＡ　（ＯりＸ　
り１　）は禁制帯幅が１６７〜３．５ｅＶと広＜、Ｇａ
Ａｓと格子整合するＧａＡｔＡｓ系レーザやＩｎＧａＡ
ｔＰ系レーザの発振波長に対して透明で、レーザ端面に
ＺｎＳＳｅ膜を形成した場合端面での光吸収による発熱
が生じない。また、熱抵抗もｚｎＳｅでは０．１９Ｗ、
　ｄｅｇ／ｃｒ１１と高く、端面での放熱性も向上する
。さらにＺｎＳｘＳｅ１−ｘの格子定数は５．６６８７
人（Ｘ＝Ｏ）〜５．４０９３　Ａ　（ｘ　＝　１　）と
Ｑ　ａ　Ａ　ｓの格子定数５．６４１９Ａに近＜ｓ　Ｑ
ａＡｓに格子整合するＧａＡｔＡＳやＩｎＧａＡｔＡｓ
上に容易にエピタキシアル成長する為、上記レーザの端
面に良好な界面を持つＺｎ８Ｓｅ膜を形成できる。比抵
抗もＩＭΩ・ｍと高くでき、端直にＺｎＳ８ｅ膜を形成
してもＺｎＳＳｅ膜を介したリーク電流は無視できるほ
ど小さい。さらに３００Ｃ前後の低温で容易にエピタキ
シアル成長する。Z n S z S e t -m PA (OoriX
1) has a wide forbidden band width of 167 to 3.5 eV.
GaAtAs lasers and InGaA that lattice match with As
It is transparent to the oscillation wavelength of the tP laser, and when a ZnSSe film is formed on the laser end face, no heat is generated due to light absorption at the end face. In addition, the thermal resistance is 0.19W for znSe,
The deg/cr is as high as 11, and the heat dissipation at the end face is also improved. Furthermore, the lattice constant of ZnSxSe1-x is 5.6687
Person (X = O) ~ 5.4093 A (x = 1) and Q a A s lattice constant close to 5.6419 A <s Q
GaAtAS and InGaAtAs that are lattice matched to aAs
Since the Zn8Se film can be easily epitaxially grown on the laser, a Zn8Se film having a good interface can be formed on the end face of the laser. The specific resistance can be made as high as IMΩ·m, and even if a ZnS8e film is directly formed, the leakage current through the ZnSSe film is negligibly small. Furthermore, epitaxial growth is easily performed at a low temperature of around 300C.

以上の特長を持つＺｎ８８ｅ膜をＧａＡｔＡＳ系および
ＩｎＧａＡｔＰｎＧａＡｔ−ザの端面に減圧ＩＶＩＯＣ
ＶＤ法にヨリ、約３００ｔｌｌ’の温度で成長した結果
、レーザ光に対して透明で、放熱性に優れ。A Zn88e film with the above features was applied to the end face of GaAtAS and InGaAtPnGaAt by low-pressure IVIOC.
As a result of growing at a temperature of approximately 300 tll' using the VD method, it is transparent to laser light and has excellent heat dissipation.

比抵抗の高い良質な膜が形成され、順方向サージ電流に
強く、また高出力動作時にも端面溶融による劣化が発生
せず、安定に動作する高出力レーザを得ることができた
。また膜形成温度が低い為。A high-quality film with high resistivity was formed, and a high-power laser that was resistant to forward surge currents and operated stably without any deterioration due to edge melting even during high-power operation was obtained. Also, the film formation temperature is low.

膜形成には電極形成後のレーザチップを用いても。A laser chip after electrode formation can also be used for film formation.

温度上昇による電極異常は発生せず、簡便なプロセスで
膜形成ができる。Electrode abnormalities do not occur due to temperature rise, and the film can be formed through a simple process.

〔実施例〕〔Example〕

以下１本発明の一実施例を第１図により説明する。第１
図は素子断面図である。く０１１ン方向に巾４μｍ、５
１さ１．５μｍのストライプ状の台形溝を４００μｍピ
ッチで形成したｎ−ＧａＡｓ（１００）基板１の上に液
相成長法により、ｎ−Ｇａｘ−ｘＡｔｚＡｓクラッド層
（ｘ＝０．４５　）　２゜Ｇ　ａｌ　−Ｆ　Ａ　ｔｙ　
Ａ　Ｓ　活性層（ｙ＝０．１３）３．　　ｐ　−Ｇ”ｔ
−ｘＡｔｘＡｓクラッド層４．ｎ−ＧａＡＳ−１！−ヤ
ツプ層５を順次成長した。その後Ｉ　ｎ−ＧａＡＳキャ
ップ層５側に、ＣＶＤ、ホトリソグラフィ工程を経て、
（０１１）方向に巾６μｍのストライプ状の拡散孔を４
００μｍピッチで形成した。次に拡散孔を通してｚｎの
拡散を行なって１台形溝直上に＆　ｎ−ＧａＡＳキャッ
プ層５を経て、　　ｐ　−Ｇ　ａｔ　−ｘ　Ａ　ｔ　ｔ
　Ａ　ｓ　クラッド層４に至る電流通路を形成した。そ
の後ｐ側電極５．　　ｎ側電極７を形成し、へき開によ
り共振器長３００μｍのレーザチップとした。An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a cross-sectional view of the element. Width 4 μm in the 011 direction, 5
An n-Gax-xAtzAs cladding layer (x=0.45) 2° is formed by liquid phase growth on an n-GaAs (100) substrate 1 on which trapezoidal grooves in the form of stripes of 1.5 μm in diameter are formed at a pitch of 400 μm. G al -F A ty
A S active layer (y=0.13)3. p −G”t
-xAtxAs cladding layer 4. n-GaAS-1! - Yap layers 5 were grown sequentially. After that, the In-GaAS cap layer 5 side was subjected to CVD and photolithography processes,
4 striped diffusion holes with a width of 6 μm in the (011) direction.
They were formed at a pitch of 00 μm. Next, zn is diffused through the diffusion hole and directly above the trapezoidal groove & through the n-GaAS cap layer 5, p -G at -x A t t
A current path reaching the A s cladding layer 4 was formed. After that, p-side electrode 5. An n-side electrode 7 was formed, and a laser chip with a cavity length of 300 μm was obtained by cleavage.

次に、チップを減圧ＭＯＣＶＤ装置に入れ。Next, the chip was placed in a low pressure MOCVD device.

３００Ｃの温度で、チップの共振器両端面にレーザ発振
波長（０，７８μｍ）のｉ波長に相当する約１５００人
のＺｎ５ｚＳｅ１−ｘ膜（０くｘく１）を形成した。ｚ
ｎＳ！Ｓｅ膜形成後、ｐ側電極を下にして、ソルダーを
介してサブマウント上にマウントした。At a temperature of 300C, about 1500 Zn5zSe1-x films (0×1) corresponding to the i wavelength of the laser oscillation wavelength (0.78 μm) were formed on both end faces of the cavity of the chip. z
nS! After forming the Se film, it was mounted on a submount via solder with the p-side electrode facing down.

以上の工程を経て作製した半導体レーザは室温連続動作
においてしきい値電流５０ｍＡで発振した。本レーザの
光出力を増し、連続動作ドにおける端面破壊限界光出力
を測定した結果、約１５００人以上の値を得た。−万、
同じウェハから作製したレーザチツプに１７２波長厚の
５ｊＯｘ膜を付着した場合の端面破壊光出力は約ａｓｍ
ｗとＺｎ５ｅ膜に較べて百であった。Ｚｎ８８ｅ膜を端
面に形成したレーザを環境温［７０Ｃにおいて。The semiconductor laser manufactured through the above steps oscillated at a threshold current of 50 mA during continuous operation at room temperature. As a result of increasing the optical output of this laser and measuring the edge destruction limit optical output in continuous operation mode, a value of about 1500 or more was obtained. Ten thousand,
When a 5jOx film with a thickness of 172 wavelengths is attached to a laser chip made from the same wafer, the edge-destroying optical output is approximately asm.
100 compared to the W and Zn5e films. A laser with a Zn88e film formed on the end face was placed at an ambient temperature of 70C.

光出力３０ｍＷで定光出力動作させた。その結果。Constant light output operation was performed with a light output of 30 mW. the result.

動作電流が初期値の２０９６増となる時を素子寿命と定
義した時の素子の平均寿命として、１０４時間以上の値
を得た。一方、１／２波長のＳｉＯ！を両端面に被着し
た素子を同じ条件で動作させた時の平均寿命は１０”〜
１０３時間と約１桁以上低いことが判明した。When the element life is defined as the time when the operating current increases by 2096 points from the initial value, a value of 104 hours or more was obtained as the average life of the element. On the other hand, 1/2 wavelength SiO! The average lifespan of a device with 200% bonded on both end faces when operated under the same conditions is 10”~
It turned out to be 103 hours, which is about an order of magnitude lower.

５ｉｎ２膜を被着した素子の劣化原因を調べたところ、
レーザ端面が溶融していることが主原因であることが判
明した。これはレーザ端面近傍で光吸収が生じ１発熱し
て生じたものと考えられる。When we investigated the cause of deterioration of the element coated with 5in2 film, we found that
It was found that the main cause was that the laser end face was melted. This is thought to be caused by light absorption near the laser end face and heat generation.

一方、ｚｎＳｅ膜を形成したレーザ素子には端面溶融に
よる劣化は認められず、ＺｎＳＳｅ膜がレーザ端面近傍
の怒構造として有効に働いていることが判明した。On the other hand, no deterioration due to end face melting was observed in the laser element on which the ZnSe film was formed, and it was found that the ZnSSe film was functioning effectively as an angular structure near the laser end face.

本発明の他の実施例を次に記す。本実施例では実施例１
のレーザチップの前方端面に１／４波長の厚さのＺｎＳ
Ｓｅ膜を形成し、後方端面に誘電体多層膜から成るパワ
ー反射率的９０％の高反射率膜を形成した。Other embodiments of the invention will be described below. In this example, Example 1
ZnS with a thickness of 1/4 wavelength is placed on the front end face of the laser chip.
A Se film was formed, and a high reflectance film with a power reflectivity of 90% consisting of a dielectric multilayer film was formed on the rear end face.

室温連続動作下で端面破壊限界光出力を測定した結果、
２００ｍＷ以上の値を得た。この値は。As a result of measuring the edge destruction limit optical output under continuous operation at room temperature,
A value of 200 mW or more was obtained. This value is.

前方端面に１／４波長相当の８ｊＣｈ膜を形成した素子
に較べて３倍以上となっていた。It was more than three times as large as the element in which an 8jCh film corresponding to 1/4 wavelength was formed on the front end face.

上記前方端面に１／４波長相当のＺｎＳＳｅ膜を、後方
端面に高反射率膜を形成した素子を７０Ｃ，５０ｍＷに
おいて定光出力動作させ九結果。The above-mentioned device, in which a ZnSSe film equivalent to a quarter wavelength was formed on the front end face and a high reflectance film on the rear end face, was operated at a constant light output of 70 C and 50 mW, and nine results were obtained.

平均寿命として、１０４時間以上の値を得た。この値は
前方端面に１７４波長相当の５ｊＣｈ膜を。The average lifespan was 104 hours or more. This value requires a 5jCh film equivalent to 174 wavelengths on the front end face.

後方端面に高反射率膜を形成した素子の平均寿命に比較
して約１桁以上長い値でめった。Compared to the average life of an element with a high reflectance film formed on the rear end face, the lifespan was approximately one order of magnitude longer.

′　〔発明の効果〕 本発明によれば、半導体レーザの端面の禁制帯巾を簡便
に広げることができるので、半導体レーザの高出力高信
頼度化の効果がある。なお。[Effects of the Invention] According to the present invention, the forbidden band width of the end face of a semiconductor laser can be easily widened, so that there is an effect of increasing the output and reliability of the semiconductor laser. In addition.

Ｚｎ　Ｓ　ｚ　Ｓ　ｔ−ｚ膜の組成としてはｘ　＝　０
．０６前後で。The composition of the Zn S z S tz film is x = 0
．． Around 06.

ＧａＡＳと室温で格子整合する場合が、素子の信頼性の
点で最も良好であったことを付記しておく。It should be noted that the case of lattice matching with GaAS at room temperature was the best in terms of device reliability.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の一実施例の半導体レーザの断面図であ
る。 １−ｎ形Ｑ　ａ　Ａ　Ｓ基板結晶、　２　・”　ｎ　　
Ｑ　ａ　１−ｚｋｔｘＡｓクラッド層、３・・・Ｇ　ａ
ｔ−ｙ　Ａ　Ｌ　ｙ　Ａ　ｓ　活性層、４・・・９　０
　ａ　１−ｍ　Ａ　Ｌ　ｘ　Ａ　８　クラッド層％　５
　・ｎ　−ＧａＡＳキャップ層、６・・・ｐ側電極、７
・・・ｎ側電極、８・・・ＺｎＳ８ｅ膜。FIG. 1 is a sectional view of a semiconductor laser according to an embodiment of the present invention. 1-n type Q a AS substrate crystal, 2 ・”n
Q a 1-zktxAs cladding layer, 3...G a
tyAlyAs active layer, 4...9 0
a 1-m A L x A 8 Cladding layer% 5
・n-GaAS cap layer, 6...p side electrode, 7
...n-side electrode, 8...ZnS8e film.

Claims (1)

【特許請求の範囲】[Claims] １、半導体レーザの少なくとも一方の端面にＺｎＳ＿ｘ
Ｓｅ＿１＿−＿ｘ（０≦ｘ≦１）を形成したことを特徴
とする半導体レーザ。1. ZnS_x on at least one end face of the semiconductor laser
A semiconductor laser characterized by forming Se_1_−_x (0≦x≦1).