JPS61272989A - Buried type semiconductor laser element - Google Patents

Abstract

PURPOSE:To improve yield on manufacture, and to accomplish stable production by forming the mesa structure of an AlGaAs multilayer thin-film with a constriction, shaping an active layer in the constriction section and burying the mesa structure by a semiconductor layer having forbidden band width wider than the active layer. CONSTITUTION:An N-type Al0.33Ga0.62As clad layer 2, an N-type Al0.32Ga0.63As guide layer 3, an undoped Al0.12Ga0.33As active layer 4, an As wetting layer 13 (0<=y<=0.1), a P-type A4l0.38Ga0.6As clad layer 6 and a P-type Al0.13Ga0.35As cap layer 7 are formed onto an N-type GaAs substrate 1 through the first crystal growth, and a narrow-width mesa shape consisting of the active layer 4 and an intermediate layer 5 is shaped through the next etching process. P-type Al0.33Ga0.62As block layers 8, 9 and a P-type Al0.33Ga0.62As buried layer 10 are formed through the second crystal growth, and mesa sections are buried. The wetting layer 13 having forbidden band width larger than the active layer is shaped onto the upper surface of a constriction section.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an embedded semiconductor laser element used as a light source in an optical fiber communication device or an optical information processing system.

(Prior art and its problems) Semiconductor lasers, which are lightweight, compact, consume little power, and can be directly modulated at high speed, are widely used as light sources for optical fiber communication devices, optical disk devices, laser beam printers, and various other optical information processing systems. I'm tired of being used. For many of these applications, a slanted light source is desired that provides stable operation in the fundamental transverse mode and also has astigmatism in the output beam. Proceedings of the Spring 1981 National Conference of the Institute of Electronics and Communication Engineers 1016
and electronic letter (Electron, Le
tt, ) 1984 Vol. 20 No. 18 728-730
The mesa (fin-type) buried structure semiconductor laser described on this page combines these two characteristics, making it the ideal semiconductor laser for use as a light source for optical information processing. However, the conventional mesa (fin type) buried structure semiconductor laser has the following problems.

FIG. 3 is a schematic cross-sectional view of a conventional semiconductor laser with a mesa constriction buried structure, which is manufactured in the following manner. First, in the first crystal growth, % It! n fJlAJ o, s s GatLs! on GaAa substrate 1! As cladding layer 2, n-type) Jo, B Gas, sa AB
Guide layer 3. Undoped AJo, tt Gao, amλ
B active layer 4, p-type AJ6,1 (ML6.@ As intermediate layer 5, pWAA!*, sa ()aO06! As cladding layer 6, pHn e*, sm Gae, ms Al!l
A cap layer 7 is formed. In the next etching step, this AJGaAs multilayer film is etched into a mesa shape. A! provided adjacent to the active layer 4! Taking advantage of the fact that the intermediate layer 5 having a large mixed crystal ratio can be selectively etched, the widths of the active layer 4 and the intermediate layer 50 are made narrower than the width of the mesa.
It has a mesa shape with constrictions on both sides. This mesa structure is
In the second crystal growth, p-type AJo, as Gas, at
As block layer Be Qt p-type Alo, as (
) allJt As embedded jfl 10. The growth of the blocking layer 9 is stopped at the constriction, resulting in the formation of an effective current confinement structure close to the active layer -4. However, in this second crystal growth, n-type AA was formed at the 9th constriction of the mesa shape! o, amG5L(1,6
! It was rare that the As buried layer 10 did not grow and cavities were formed on the sides of the active layer 4 and intermediate layer 5.

Due to the generation of cavities, the refractive index difference between the active layer 4 and the cavity portion is too large, leading to higher-order transverse modes, and furthermore,
Problems such as deterioration occurred from the exposed side surfaces of the active layer 4 occurred. The production of cavities lowers the manufacturing yield of devices, and their irregular occurrence has been an obstacle to stable production of semiconductor lasers with a mesa-constriction-embedded structure.

The causes of cavities are thought to be as follows.

The second buried growth is performed using the liquid phase growth method, but the liquid phase growth method has a property that epitaxial growth on the surface of the AlGaAa layer that has been subjected to treatments such as etching becomes more difficult as the Al mixed crystallization increases. be. The constriction of the mesa structure has Aje, ma ()allj on the top surface.
! Person 8 Cladding layer 6. AJa, sea on the side.
As intermediate layer 5, AnoOjl Ga (148As
The guide layer 3 is exposed, and the Al mixed crystal ratio of these layers is as large as 0.3 or more. Furthermore, the effect of the constricted shape increases the difficulty of crystal growth in the constricted part, and it is thought that cavities are created. It is an object of the present invention to provide a mesa (fin type) buried semiconductor laser device which solves the above problems and can be produced stably with a high manufacturing yield.

(Means for Solving the Problems) In order to solve the above-mentioned problems, an embedded semiconductor laser device provided by the present invention uses a constricted AlGaA
s A semiconductor that has a mesa structure of a multilayer thin film, the active layer is located at the constriction, and at least one of the upper or downward crystal planes exposed at the constriction has an M mixed crystal ratio of 0.1 or less. It is characterized by a mesa structure in which both the active layer and the active layer are filled with a semiconductor layer with a wide forbidden band width.

(Embodiment) FIG. 1 is a schematic cross-sectional view of the first embodiment of the present invention.
n-type AJo, sa ()at on nya GaAs substrate 1
lJIAs cladding layer 2, n-type Alo, sa GaO
3@@ As guide layer 3, undoped AJo, tt G
oo, as As active layer 4, p-type AlO, I Ga0.
,, As intermediate layer 5, p* AlyGa 1-yA
s wetting layer 13 (0≦y≦0.1), p-type Alo, s a Gao, s t As cladding layer 6% p-type Alo, ti()aO1a! The As cap layer 7 is formed in the first crystal growth, and in the next etching step, the active layer 4 and the intermediate layer 50 are formed into a narrow mesa shape.

In the second crystal growth, p-type Alo, sa Gas, at
As block layer Be 9t p-type Aj6. H()a
A full As buried layer 10 is formed to bury the mesa portion. In this second crystal growth, a wetting layer 13 having an M composition ratio smaller than 0.1 is exposed on the upper surface of the constriction. There is a property that liquid phase growth on the AJGaAs layer becomes much easier when Al mixed crystallization becomes 0.1 or less. In this example, with the help of the wetting layer 13 which is easy to grow, AJo, a
s ( ) a ( 1, at Al buried layer 10 grows easily. As a result, the occurrence of cavities at the neck can be significantly reduced, and semiconductor lasers with a mesa neck buried structure can be produced stably with high yield. It became possible to do so.

If the forbidden band width of the quetting layer 13 is narrower than that of the active layer, there is a concern that part of the oscillated light will be absorbed by the queting layer 13, leading to an increase in the threshold value and a decrease in efficiency. However, in the optical waveguide of this embodiment, if the thickness of the intermediate layer 5 is set to 0.3 μm or more, almost no oscillated light reaches the wetting layer 13, and the oscillation characteristics are not impaired.

The same applies to elements having other optical waveguide structures. Therefore, according to this embodiment, a low threshold value and high efficiency comparable to those of the mesa constriction type buried structure semiconductor laser of the conventional structure can be achieved. Moreover, this embodiment is the same as the conventional structure in that it has excellent transverse mode stability and output light without astigmatism can be obtained.

FIG. 2 is a schematic cross-sectional view of a second embodiment of the invention.

In this example, after crystal growth to the same layer structure as in the first example, p-type impurity is selectively diffused from the crystal surface to form a region wider than the mesa portion and deeper than the questing layer 13. The conductivity type is p-type throughout. The carrier concentration in the diffusion region is high, which not only reduces device resistance but also improves insulation properties. ! 115 can be expanded to the width of the diffusion region, improving heat dissipation characteristics.

In the two embodiments described above, an AJGaAs layer with an AJ crystal ratio of 0.1 or less was used as the wetting layer, but Al()aP with a kl mixed crystal ratio of 0.1 or less or no AJ was used. Similar effects can be achieved by using an InGaAsP layer.

(Effects of the Invention) As explained above, the buried semiconductor laser device of the present invention has the characteristics of the conventional mesa buried structure laser that it can provide output with a low threshold value, high efficiency, and no astigmatism. While maintaining this, the instability of manufacturing yields associated with conventional devices has been resolved, achieving high yields and, in turn, making it possible to significantly reduce manufacturing costs.

[Brief explanation of drawings]

1 and 2 are schematic sectional views of first and second embodiments of the present invention, and FIG. 3 is a schematic sectional view of a conventional element.卜00n type GaAs substrate t2°”n type kl@, am e
ao, atAs'ri 2 rad layer, 3...n board AJ
o,s Feces Ga QJ I As guide layer, 4...
Alo, xt Gas, as As active layer, s/p
Type AJ@, I As intermediate layer, 6p type AA! e, as (
) ao, HAs cladding layer, 7-p type AJe, ss
()5Le, as As cap layer, 8-I) type Al
o, s Gas, at As block layer, 9.
...p-type Alo, sa ()am, @* As block layer, 10-n-type Alo, sa ()ao, st
kB buried layer, 11-1) side electrode. 12-n side electrode, 13”・1) fIiAlGa,
-yAsAs uniting layer (0≦y≦0.1), 14-... p-type impurity diffusion region, 15-... insulating thin film. Agent Patent Attorney Shinsuke Honjo No. 1, Figure 1

Claims (1)

[Claims] It has a mesa structure of a constricted AlGaAs multilayer thin film,
The active layer is located in the constriction, at least one of the upper or lower crystal planes exposed in the constriction is a semiconductor layer with an Al mixed crystal ratio of 0.1 or less, and the mesa structure is in the active layer. An embedded semiconductor laser element characterized in that it is embedded with a semiconductor layer having a wider forbidden band width.