【０００１】[0001]
【産業上の利用分野】この発明は半導体レーザに関し、
特に、活性層に垂直な方向にレーザ出力光を生ずる面発
光半導体レーザに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser,
In particular, the present invention relates to a surface emitting semiconductor laser that generates laser output light in a direction perpendicular to the active layer.
【０００２】[0002]
【従来の技術】一つの導電型のIII-V 族化合物半導体
（例えばｎ型ＧａＡｓ）の基板の表面に、同一導電型の
下側反射膜、量子井戸から成る活性層、反対導電型の上
側反射膜、および金属膜をエピタキシャル成長により形
成し、基板と金属膜との間に直流電圧を印加して、基板
の下面（裏面）または上側反射膜の上面からその面と垂
直な方向にレーザ出力光を取り出す構成の面発光半導体
レーザが注目を集めている。この種の半導体レーザの構
造は、ＩＣ製造技術の応用により単一の基板に多数の微
小レーザを高度に集積化することを可能にするので、信
号伝送路の光スイッチや光コンピュータなどに広く応用
できるものと期待されている。2. Description of the Related Art A lower reflective film of the same conductivity type, an active layer composed of a quantum well, and an upper reflection type of the opposite conductivity type are formed on the surface of a III-V compound semiconductor (for example, n-type GaAs) of one conductivity type. A film and a metal film are formed by epitaxial growth, a DC voltage is applied between the substrate and the metal film, and laser output light is emitted from the lower surface (back surface) of the substrate or the upper surface of the upper reflective film in a direction perpendicular to the surface. Attention has been paid to a surface emitting semiconductor laser having a configuration for taking out light. This type of semiconductor laser structure enables a large number of microlasers to be highly integrated on a single substrate by applying IC manufacturing technology, so it is widely applied to optical switches in signal transmission lines, optical computers, etc. It is expected to be possible.
【０００３】しかしながら、このような面発光半導体レ
ーザを実用的な形で実現するには消費電力を低減しなけ
ればならない。すなわち、微分量子効率（内部量子効率
とミラー損失対光共振器内損失比との積）を高めて閾値
電流を低減するとともに、上記基板と金属膜との間の電
気抵抗を下げて駆動電源電圧を低下させなければならな
い。However, in order to realize such a surface emitting semiconductor laser in a practical form, the power consumption must be reduced. That is, the differential quantum efficiency (the product of the internal quantum efficiency and the mirror loss to the loss ratio in the optical resonator) is increased to reduce the threshold current, and the electric resistance between the substrate and the metal film is reduced to reduce the driving power supply voltage. Must be reduced.
【０００４】[0004]
【発明が解決しようとする課題】そこで、閾値電流およ
び電気抵抗の低減のためのいろいろの手法が提案されて
きた。まず、Ｅｌｅｃｔｒｏｎｉｃｓ Ｌｅｔｔｅｒ
ｓ，ｖｏｌ．２５，ｐｐ，ｐｐ．１３７７−１３７８
（１９８９年）所載のＪ．Ｌ．Ｊｅｗｅｌｌらの報告
は、上記下側反射膜および上側反射膜として多層ＧａＡ
ｓ／ＡｌＡｓ膜による分布Ｂｒａｇｇ反射膜（Ｄｉｓｔ
ｒｉｂｕｔｅｄ Ｂｒａｇｇ Ｒｅｆｌｅｃｔｏｒｓ，
以下ＤＢＲ反射膜という）を採用することが閾値電流の
低下に非常に有効であることを示した。ＤＢＲ反射膜の
採用は確かに閾値電流の低減をもたらすが、電気抵抗の
低減は充分でない。電気抵抗を下げる手段として、ＩＥ
ＥＥ Ｐｈｏｔｏｎｉｃｓ Ｔｅｃｈｎｏｌｏｇｉｃａ
ｌ Ｌｅｔｔｅｒｓ，ｖｏｌ．２，ｐｐ．２３４−２３
６（１９９０年）所載のＲ．Ｓ．Ｇｅｅｌｓらの報告、
および上記Ｊ．Ｌ．Ｊｅｗｅｌｌらによる米国特許第
４，９４９，３５０号は、上記下側反射膜および上側反
射膜を構成するＤＢＲ反射膜のＧａＡｓ／ＡｌＡｓヘテ
ロ接合部にグレーデット層を形成することを提案した。
ＤＢＲ反射膜の高い電気抵抗が、そのＤＢＲ反射膜を構
成する多層ＧａＡｓ／ＡｌＡｓ膜の各々のＧａＡｓ／Ａ
ｌＡｓヘテロ接合の高抵抗に起因することに着目した提
案であるこの手法によって上述の抵抗値は従来の１０分
の１程度に低減できる見通しである旨報告されている
が、それ以上の低減は困難とみられる。Therefore, various methods for reducing the threshold current and the electric resistance have been proposed. First, Electronics Letter
s, vol. 25, pp, pp. 1377-1378
(1989). L. Jewell et al. Reported that multilayer GaAs was used as the lower reflective film and the upper reflective film.
Distributed Bragg reflection film (Dist) by s / AlAs film
ribbed Bragg Reflectors,
It is shown that the use of a DBR reflection film) is very effective in lowering the threshold current. Although the adoption of the DBR reflective film certainly reduces the threshold current, it does not sufficiently reduce the electric resistance. IE as a means to reduce electrical resistance
EE Photonics Technology
l Letters, vol. 2, pp. 234-23
6 (1990). S. Reports by Geels et al.
And J. above. L. U.S. Pat. No. 4,949,350 to Jewell et al. Proposed forming a graded layer at the GaAs / AlAs heterojunction of the DBR reflective film constituting the lower reflective film and the upper reflective film.
The high electrical resistance of the DBR reflection film is due to the GaAs / A of each of the multilayer GaAs / AlAs films constituting the DBR reflection film.
It has been reported that this technique, which is a proposal focusing on the high resistance of the lAs heterojunction, is expected to reduce the above-described resistance value to about one tenth of the conventional value, but further reduction is difficult. It seems to be.
【０００５】電気抵抗を下げるもう一つの手法は、Ｅｌ
ｅｃｔｒｏｎｉｃｓ Ｌｅｔｔｅｒｓ，ｖｏｌ．２７，
ｐｐ．９５１−９１６（１９９１年）所載のＧ．Ｈａｓ
ｎａｉｎらの報告にも記載されているとおり、ＤＢＲ反
射膜を構成する多層ＧａＡｓ／ＡｌＡｓ膜の不純物濃度
を上げる手法である。このアプローチによると、電気抵
抗は確かに下がるものの、光共振器内のフリーキャリア
による光の吸収が不可避的に大きくなり、微分量子効率
が下り、閾値電流を引き上げる。[0005] Another method for lowering the electric resistance is El.
electronics Letters, vol. 27,
pp. G. 951-916 (1991). Has
As described in the report of Nain et al., this is a method of increasing the impurity concentration of the multilayer GaAs / AlAs film constituting the DBR reflection film. According to this approach, although the electrical resistance certainly decreases, the absorption of light by the free carriers in the optical resonator inevitably increases, the differential quantum efficiency decreases, and the threshold current increases.
【０００６】この発明の目的は、微分量子効率の低下を
伴うことなく電気抵抗を低減したＤＢＲ反射膜ベースの
面発光半導体レーザを提供することにある。An object of the present invention is to provide a surface emitting semiconductor laser based on a DBR reflective film which has reduced electric resistance without lowering differential quantum efficiency.
【０００７】[0007]
【課題を解決するための手段】この発明によるＤＢＲ反
射膜ベースの面発光半導体レーザにおいて、ＤＢＲ反射
膜を構成する多層ＧａＡｓ／ＡｌＡｓ膜の不純物濃度を
上記Ｈａｓｎａｉｎらの提案のように均一に上げる代り
に、光共振器内に発生する活性層からの出力光の定在波
の電界強度が最小になる点のみにおいて選択的に上げ
る。出力光定在波の電界強度の最小値は光共振器の軸方
向、すなわち活性層面に垂直な方向に空間的に周期的に
現われるので、この空間的周期とＤＢＲ反射膜の多層Ｇ
ａＡｓ／ＡｌＡｓ膜の厚さとを一対一に対応させ、それ
ら多層ＧａＡｓ／ＡｌＡｓ膜のＧａＡｓ／ＡｌＡｓヘテ
ロ接合のうち、レーザ全体の順バイアス動作時に逆バイ
アス状態になるＧａＡｓ／ＡｌＡｓヘテロ接合のみで不
純物濃度を高める。In the surface emitting semiconductor laser based on the DBR reflection film according to the present invention, instead of uniformly increasing the impurity concentration of the multilayer GaAs / AlAs film constituting the DBR reflection film as proposed by Hasnain et al. Then, the intensity is selectively increased only at the point where the electric field intensity of the standing wave of the output light from the active layer generated in the optical resonator is minimized. Since the minimum value of the electric field strength of the output light standing wave appears spatially and periodically in the axial direction of the optical resonator, that is, in the direction perpendicular to the active layer surface, this spatial period and the multilayer G of the DBR reflection film are considered.
The thickness of the aAs / AlAs film is made to correspond to one-to-one, and among the GaAs / AlAs heterojunctions of the multilayer GaAs / AlAs films, only the GaAs / AlAs heterojunction which is in a reverse biased state when the laser as a whole is forward biased has an impurity concentration. Enhance.
【０００８】[0008]
【作用】この発明の面発光半導体レーザのＤＢＲ反射膜
を形成する多層ＧａＡｓ／ＡｌＡｓ膜は上述のとおり逆
バイアス状態なるヘテロ接合近傍で高濃度に不純物を含
むので、それらヘテロ接合に起因する高抵抗値を低減で
きる。また、上記光定在波の電界強度の高い点では不純
物濃度は低く抑えてあるので光共振器内フリーキャリア
による光の吸収損失を低減でき、微分量子効率の低下を
回避できる。すなわち、この発明によれば、微分量子効
率を害なうことなく電気抵抗を低減した面発光半導体レ
ーザが得られる。The multilayer GaAs / AlAs film forming the DBR reflection film of the surface emitting semiconductor laser according to the present invention contains impurities in high concentration near the hetero-junction in the reverse bias state as described above. Value can be reduced. Further, since the impurity concentration is kept low at the point where the electric field strength of the optical standing wave is high, the absorption loss of light due to free carriers in the optical resonator can be reduced, and a decrease in differential quantum efficiency can be avoided. That is, according to the present invention, it is possible to obtain a surface emitting semiconductor laser having reduced electric resistance without deteriorating differential quantum efficiency.
【０００９】[0009]
【実施例】図１Ａを参照すると、この図に縦断面図を示
した本発明の面発光半導体レーザは、ｎ型ＧａＡｓ基板
１の表面に、ｎ型多層干渉反射膜４、活性領域３、ｐ型
多層干渉反射膜４および位相制御層５を分子線エピタキ
シー（ＭＢＥ）により順次エピタキシャル成長させて形
成した積層構造にＡｕＺｎ膜を堆積したのち、この積層
構造物をドライエッチングにかけて、各々が直径１〜１
０μｍを有し、基板１の１つの面に配置された多数の円
柱状の微小レーザに切り分けることによって製造する。
この積層構造物の形成のための製造工程は上述の従来技
術と実質的に共通であるので詳細な説明は省略する。な
お、電極用ＡｕＺｎ膜６の形成は、ドライエッチングに
よる微小レーザへの切分けの後に行っても差し支えな
い。ＧａＡｓ基板１の下側の面（裏面）にはＡｕＧｅＮ
ｉから成る環状の電極７を形成する。この半導体レーザ
の駆動直流電圧は電極６を＋、電極７を−として印加さ
れ、レーザ光８はＧａＡｓ基板１の上記裏面から取り出
される。FIG. 1A is a longitudinal sectional view of a surface emitting semiconductor laser according to the present invention. An n-type GaAs substrate 1 has an n-type multilayer interference reflection film 4, an active region 3, AuZn film is deposited on a multilayer structure formed by sequentially epitaxially growing the multilayer interference reflection film 4 and the phase control layer 5 by molecular beam epitaxy (MBE).
It is manufactured by cutting into a large number of cylindrical microlasers having a thickness of 0 μm and arranged on one surface of the substrate 1.
The manufacturing process for forming the laminated structure is substantially the same as that of the above-described conventional technology, and thus a detailed description is omitted. The formation of the electrode AuZn film 6 may be performed after separation into minute lasers by dry etching. AuGeN on the lower surface (back surface) of the GaAs substrate 1
An annular electrode 7 made of i is formed. The driving DC voltage of the semiconductor laser is applied with the electrode 6 being positive and the electrode 7 being negative, and the laser light 8 is extracted from the back surface of the GaAs substrate 1.
【００１０】活性領域３は、厚さ１０ｎｍで不純物を含
まないＩｎ0.2Ｇａ0.8Ａｓから成る活性層１０を、Ｓ
ｉで５×１０16ｃｍ-3の濃度にドープされた厚さ１４３
ｎｍのｎ型Ａｌ0.5Ｇａ0.5層１１と、Ｂｅで５×１０
16ｃｍ-3の濃度にドープされた厚さ１４３ｎｍのｐ型Ａ
ｌ0.5Ｇａ0.5Ａｓ層１２とで挟んだサンドウィッチ構
造を備えている。The active region 3 includes an active layer 10 made of In0.2 Ga0.8 As and having a thickness of 10 nm and containing no impurities.
a thickness 143 doped with i to a concentration of 5 × 1016 cm-3
nm type Al0.5 Ga0.5 layer 11 and 5 × 10
143 nm thick p-type A doped to a concentration of16 cm-3
A sandwich structure sandwiched between the l0.5 Ga0.5 As layer 12 is provided.
【００１１】位相制御層５は、活性領域３からの光の電
極６における反射に伴う位相変化を補償してｐ型多層干
渉反射膜４の反射率を最大にするための層であり、その
厚さは活性領域３からのレーザ光の波長λ0の０．１６
倍を位相制御層５の屈折率で除した値に選ぶ。本実施例
においては、位相制御層５を構成するｐ型ＧａＡｓ層の
屈折率は３．５４４１６であり、波長λ0は９５０ｎｍ
であるので層５の厚さは４２．８８ｎｍに選んである。The phase control layer 5 is a layer for maximizing the reflectivity of the p-type multilayer interference reflection film 4 by compensating for a phase change caused by the reflection of light from the active region 3 on the electrode 6, and having a thickness of Is 0.16 of the wavelength λ0 of the laser beam from the active region 3.
Select a value obtained by dividing the magnification by the refractive index of the phase control layer 5. In this embodiment, the refractive index of the p-type GaAs layer constituting the phase control layer 5 is 3.554416, and the wavelength λ0 is 950 nm.
Therefore, the thickness of the layer 5 was selected to be 42.88 nm.
【００１２】ｎ型多層干渉反射膜２は、それぞれＳｉで
従来技術による場合と同程度の濃度にドープしたｎ型Ｇ
ａＡｓ層１３とｎ型ＡｌＡｓ層１４とを交互に２３周期
にわたり積層して形成したＤＢＲである。同様に、ｐ型
多層干渉反射膜４は、それぞれＢｅで従来技術による場
合と同程度の濃度にドープしたｐ型ＧａＡｓ層１５とｐ
型ＡｌＡｓ層１６とを交互に１５周期にわたり積層して
形成したＤＢＲである。これらＧａＡｓ層およびＡｌＡ
ｓ層の厚さは、それぞれλ0／ｎGaAs，λ0／ｎAlAsに
選ぶ。ここで、ｎGaAsおよびｎAlAsは、それぞれＧａＡ
ｓおよびＡｌＡｓの屈折率を表わす。ｎGaAsおよびｎ
AlAsは導電型にほぼ関係なく、それぞれ３．５４４１６
および２．９６０９１であるので、この実施例ではＧａ
Ａｓ層の厚さは６７ｎｍに、ＡｌＡｓ層の厚さは８０．
２ｎｍにそれぞれ選んである。The n-type multilayer interference reflection film 2 is made of n-type G doped with Si at the same concentration as in the prior art.
This is a DBR formed by alternately stacking aAs layers 13 and n-type AlAs layers 14 for 23 periods. Similarly, the p-type multilayer interference reflection film 4 is composed of a p-type GaAs layer 15 and a p-type GaAs layer 15 doped with Be at the same concentration as in the prior art.
It is a DBR formed by alternately laminating the type AlAs layers 16 for 15 periods. These GaAs layer and AlA
The thickness of the s layer is selected to be λ0 / nGaAs and λ0 / nAlAs , respectively. Here, nGaAs and nAlAs areGaAs , respectively.
s and the refractive index of AlAs. nGaAs and n
AlAs is 3.554416 regardless of the conductivity type.
And 2.96091, Ga in this embodiment.
The thickness of the As layer is 67 nm, and the thickness of the AlAs layer is 80 nm.
Each was selected to 2 nm.
【００１３】次に、図１Ｂおよび図１Ｃを図１Ａに併せ
て参照すると、多層干渉反射膜２および４の各々を構成
するＧａＡｓ層およびＡｌＡｓ層は、上述の均一なドー
ピングに加えて、これら層の間のＧａＡｓ／ＡｌＡｓヘ
テロ接合のうち、特定のヘテロ接合およびその近傍を高
濃度にドーピングする。すなわち、これらＧａＡｓ／Ａ
ｌＡｓヘテロ接合のうち、多層干渉反射膜２および４か
らそれぞれ活性領域３に向って、小さい値から大きい値
に変化する禁制帯幅Ｅｇをもつヘテロ接合１７およびそ
れら接合近傍において、Ｓｉ（ｎ型多層干渉反射膜２）
およびＢｅ（ｐ型多層干渉反射膜４）で高濃度にドープ
する。高濃度にドープされたこれらヘテロ接合１７は、
この面発光半導体レーザの電極６および電極７の間に順
方向に直流電圧をかけた状態で逆バイアスになる接合で
あり、活性領域３、多層干渉反射膜２および４にわたっ
て発生するレーザ光の定在波の電界強度２０の最小点に
位置する。この実施例におけるｎ型多層干渉反射膜で
は、ｎ型ＡｌＡｓ ｏｎｎ型ＧａＡｓのヘテロ接合が、
また、ｐ型多層板反射膜４ではｐ型ＧａＡｓ ｏｎｐ型
ＡｌＡｓのヘテロ接合が上記特定のヘテロ接合１７を構
成する。これら特定のヘテロ接合１７に形成される高濃
度ドープ領域１８（図１Ｃ）は、ｎ型およびｐ型多層干
渉反射膜２および４の両方共、６０ｎｍの厚さをもち、
前者で５×１０18ｃｍ-3後者で１×１０19ｃｍ-3の不純
物濃度をもつ（図１Ｄ）。これら高濃度ドープ領域１８
以外の部分は多層干渉反射膜２および４ともに１×１０
18ｃｍ-3に均一にドープしている。Next, referring to FIGS. 1B and 1C in conjunction with FIG. 1A, the GaAs layer and the AlAs layer constituting each of the multilayer interference reflection films 2 and 4 have these layers in addition to the above-mentioned uniform doping. In the GaAs / AlAs heterojunction between the above, a specific heterojunction and its vicinity are heavily doped. That is, these GaAs / A
In the 1As heterojunction, a heterojunction 17 having a forbidden band width Eg that changes from a small value to a large value from the multilayer interference reflection films 2 and 4 toward the active region 3 respectively, and Si (n-type multilayer) near the junction. Interference reflection film 2)
And Be (p-type multilayer interference reflection film 4) at a high concentration. These heavily doped heterojunctions 17
This junction is reverse biased when a DC voltage is applied in the forward direction between the electrode 6 and the electrode 7 of the surface emitting semiconductor laser, and the constant of laser light generated over the active region 3 and the multilayer interference reflection films 2 and 4 is constant. It is located at the minimum point of the electric field strength 20 of the standing wave. In the n-type multilayer interference reflection film in this embodiment, the heterojunction of n-type AlAs on-type GaAs is
Further, in the p-type multilayer board reflection film 4, the heterojunction of p-type GaAs on p-type AlAs constitutes the specific heterojunction 17. The heavily doped region 18 (FIG. 1C) formed in these specific heterojunctions 17 has a thickness of 60 nm for both the n-type and p-type multilayer interference reflection films 2 and 4, and
The former has an impurity concentration of 5 × 1018 cm−3 and the latter has an impurity concentration of 1 × 1019 cm−3 (FIG. 1D). These heavily doped regions 18
The other parts are 1 × 10 for both the multilayer interference reflection films 2 and 4.
It is uniformly doped to18 cm-3 .
【００１４】電極６および７を上述のとおり駆動電源
（図示していない）の陽極および陰極にそれぞれ接続す
ると、この半導体レーザはレーザ発振を起し、ｎ型Ｇａ
Ａｓ基板１の裏面から出力光８を発生する。多層干渉反
射膜２および４を構成する上記ＤＢＲｓのＧａＡｓ／Ａ
ｌＡｓヘテロ接合は、この状態で１層ごとに交互に順バ
イアス状態および逆バイアス状態となる。一般に、逆バ
イアス状態にあるヘテロ接合は電流が流れにくく、高抵
抗になるが、本実施例では、これら逆バイアスになるヘ
テロ接合の近傍は高濃度に不純物でドープしてあるの
で、電流は流れ易く、上記高抵抗は回避できる。しか
も、高濃度ドープ領域１８は上記光定在波の電界強度の
最小点の近傍に限って形成してあるので、それら高濃度
ドープ領域１８のフリーキャリアによる光の吸収の影響
は最小限に抑えられ、微分量子効率の低下を招くことは
ない。When the electrodes 6 and 7 are connected to the anode and the cathode of a drive power supply (not shown), respectively, as described above, the semiconductor laser oscillates and n-type Ga
The output light 8 is generated from the back surface of the As substrate 1. GaAs / A of the above DBRs constituting the multilayer interference reflection films 2 and 4
In this state, the 1As heterojunction alternately becomes a forward bias state and a reverse bias state for each layer. In general, a heterojunction in a reverse bias state hardly allows a current to flow and has a high resistance. However, in the present embodiment, the vicinity of the reverse biased heterojunction is heavily doped with impurities. It is easy to avoid the high resistance. Moreover, since the heavily doped region 18 is formed only in the vicinity of the minimum point of the electric field intensity of the light standing wave, the influence of light absorption by free carriers in the heavily doped region 18 is minimized. Therefore, the differential quantum efficiency does not decrease.
【００１５】本実施例において、閾値電流密度は９００
Ａ／ｃｍ2になり、従来技術による値（１．５ＫＡ／ｃ
ｍ2）に比べて大幅に改善されている。また、多層干渉
反射膜のシート電気抵抗ρsは、従来技術による多層干
渉反射膜１０周期の構成で２．３×１０-4Ω・ｃｍ2で
あったものが、１／２程度になる。In this embodiment, the threshold current density is 900
A / cm2, which is a value obtained by the conventional technology (1.5 KA / c
m2 ). Further, the sheet electric resistance ρs of the multilayer interference reflection film is about1/2 , which is 2.3 × 10−4 Ω · cm2 in the configuration of the conventional multilayer interference reflection film having 10 periods.
【００１６】下側反射膜２のｎ型ＤＢＲを２８．５周
期、上側反射膜４のｐ型ＤＢＲを２３周期とし、上記高
濃度ドープ領域１８の不純物濃度を上側反射膜４で５×
１０18ｃｍ-3、下側反射膜２で２×１０18ｃｍ-3とし、
上記高濃度ドープ領域１８以外の均一ドープ領域の不純
物濃度を５×１０17ｃｍ-3とし、エッチングにより２０
μｍ×２０μｍの角柱に加工して構成した本実施例によ
るサンプルでは、室温ＣＷ発振で閾値電流１．８ｍＡ、
閾値電流密度４５０Ａ／ｃｍ2、微分量子効率０．１ｍ
Ｗ／ｍＡをそれぞれ記録した。閾値電流および電気抵抗
について上述の改善がみられたほか、微分量子効率も従
来技術によった場合に比べて１０倍程度改善されている
ことがわかる。The n-type DBR of the lower reflective film 2 is 28.5 periods, the p-type DBR of the upper reflective film 4 is 23 periods, and the impurity concentration of the heavily doped region 18 is 5 × in the upper reflective film 4.
1018 cm-3, and 2 × 1018 cm-3 in the downside reflecting film 2,
The impurity concentration of the uniformly doped region other than the highly doped region 18 was set to 5 × 1017 cm−3 ,
In the sample according to the present embodiment formed into a prism having a size of μm × 20 μm, the threshold current is 1.8 mA at room temperature CW oscillation, and the threshold current is 1.8 mA.
Threshold current density 450 A / cm2 , differential quantum efficiency 0.1 m
W / mA was recorded respectively. It can be seen that, in addition to the above-mentioned improvements in the threshold current and the electric resistance, the differential quantum efficiency has been improved about 10 times as compared with the case of the prior art.
【００１７】本実施例においては、ｐ型多層干渉反射膜
４およびｎ型多層干渉反射膜２の両方において、上記高
濃度ドープ領域１８を形成したが、これら反射膜２およ
び４のいずれか一方だけに形成しても差し支えない。そ
の場合は、ｐ型多層干渉反射膜４に高濃度ドープ領域１
８を形成するのが、好ましい。なぜなら、ｐ型多層干渉
反射膜４の方が直列抵抗が１桁程度高く、かつ、フリー
キャリア損失も大きいからである。また、この発明によ
る周期的高濃度ドープ領域１８の形成を上記の従来技術
によるＧａＡｓ／ＡｌＡｓ接合部でのグレーデット層の
形成に併せて行うこともできる。その場合は、直列抵抗
の低減効果がさらに高まる。また、活性領域３に２つ以
上の量子井戸活性層を含めることもでき、また、ｐｎｐ
ｎ構造にすることもできる。後者の場合には、ｐｎｐｎ
構造特有のスイッチング特性が生じ、レーザ発振とスイ
ッチングの２つの機能を有する面発光半導体レーザが得
られる。また、本実施例では、ドーパントとしてＳｉお
よびＢｅを用いたが、Ｓｎ，Ｔｅ，Ｍｎ，Ｍｇ，Ｚｎ等
も同様に用いる事ができる。また、本発明に用いられる
III-V 族半導体材料は、実施例では、ＧａＡｓ，ＡｌＡ
ｓに限ったが、ＩｎＧａＡｓＰ／ＩｎＰ系等のIII-V 族
半導体材料も同様に用いることができる。また、基板裏
面からレーザ光を取り出す構造としたが、上側ＤＢＲ反
射膜上面からレーザ光を取り出す構造にしても差し支え
ない。In this embodiment, the heavily doped region 18 is formed in both the p-type multilayer interference reflection film 4 and the n-type multilayer interference reflection film 2, but only one of these reflection films 2 and 4 is formed. May be formed. In that case, the heavily doped region 1
Preferably, 8 is formed. This is because the p-type multilayer interference reflection film 4 has a higher series resistance by about one digit and a larger free carrier loss. In addition, the formation of the periodically heavily doped region 18 according to the present invention can be performed simultaneously with the formation of the graded layer at the GaAs / AlAs junction according to the above-described prior art. In that case, the effect of reducing the series resistance is further enhanced. Further, the active region 3 can include two or more quantum well active layers, and the pnp
An n-structure can also be used. In the latter case, pnpn
A switching characteristic peculiar to the structure occurs, and a surface emitting semiconductor laser having two functions of laser oscillation and switching can be obtained. Further, in the present embodiment, Si and Be are used as dopants, but Sn, Te, Mn, Mg, Zn and the like can be used in the same manner. Also used in the present invention
In the embodiment, the III-V group semiconductor material is GaAs, AlA.
Although limited to s, III-V group semiconductor materials such as InGaAsP / InP can be used in the same manner. Further, although the structure is such that the laser light is extracted from the back surface of the substrate, the structure may be such that the laser light is extracted from the upper surface of the upper DBR reflective film.
【００１８】[0018]
【発明の効果】以上説明したように、本発明において
は、光定在波の節となる位置と前述した逆バイアスとな
るヘテロ接合位置が一致している事を利用して、このヘ
テロ接合部にのみ不純物を多量にドープする事によって
微分量子効率を悪化させる事なく電気抵抗を低減する事
が出来る。As described above, in the present invention, by utilizing the fact that the position of the node of the optical standing wave coincides with the position of the heterojunction which becomes the reverse bias, the heterojunction portion is used. By doping a large amount of the impurity only, the electrical resistance can be reduced without deteriorating the differential quantum efficiency.
【図１】Ａは発明の一実施例の面発光半導体レーザの構
造を模式的に示す縦断面図、ＢはＡの半導体レーザの動
作状態でその内部に発生する光定在波の電界強度のＡの
半導体レーザ軸方向位置に対する分布を示す図、ＣはＡ
の半導体レーザを構成する多層干渉反射膜及び活性領域
の各々に対応する禁制帯幅と上記多層干渉反射膜の高不
純物濃度領域との関係を模式的に示す図、Ｄは上記多層
干渉反射膜の不純物濃度のＢと同様の軸方向位置に対す
る分布の一例を示す図である。FIG. 1A is a longitudinal sectional view schematically showing a structure of a surface emitting semiconductor laser according to one embodiment of the invention, and FIG. 1B is a graph showing the electric field intensity of a light standing wave generated inside the semiconductor laser of FIG. FIG. 4 shows a distribution of A with respect to a position in a semiconductor laser axial direction, and FIG.
FIG. 4 schematically shows a relationship between a band gap corresponding to each of the multilayer interference reflection film and the active region constituting the semiconductor laser of the present invention and a high impurity concentration region of the multilayer interference reflection film. It is a figure which shows an example of the distribution with respect to the axial position similar to B of an impurity concentration.
１ 半導体基板 ２ ｎ型ＤＢＲ反射膜 ３ 活性領域 ４ ｐ型ＤＢＲ反射膜 ５ 位相制御層 ６ 電極 ７ 電極 １７ 高濃度ドープのヘテロ接合 １８ 高濃度領域 ２０ 光定在波 REFERENCE SIGNS LIST 1 semiconductor substrate 2 n-type DBR reflection film 3 active region 4 p-type DBR reflection film 5 phase control layer 6 electrode 7 electrode 17 heavily doped heterojunction 18 high concentration region 20 light standing wave
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.6，ＤＢ名) H01S 3/18 ＪＩＣＳＴファイル（ＪＯＩＳ)──────────────────────────────────────────────────の Continued on the front page (58) Field surveyed (Int.Cl.6 , DB name) H01S 3/18 JICST file (JOIS)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3329099AJP2757633B2 (en) | 1990-12-28 | 1991-12-12 | Surface emitting semiconductor laser |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP41693090 | 1990-12-28 | ||
| JP2-416930 | 1990-12-28 | ||
| JP3329099AJP2757633B2 (en) | 1990-12-28 | 1991-12-12 | Surface emitting semiconductor laser |
| Publication Number | Publication Date |
|---|---|
| JPH0629611A JPH0629611A (en) | 1994-02-04 |
| JP2757633B2true JP2757633B2 (en) | 1998-05-25 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3329099AExpired - LifetimeJP2757633B2 (en) | 1990-12-28 | 1991-12-12 | Surface emitting semiconductor laser |
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