JPH01274488A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To conduct re-growth having excellent crystallizability, and to improve reliability by forming a trench for a current path while leaving one part of a current block layer, melting back a region left to a thin-film shape in the region of the trench for the current path through a melt-back technique by a liquid-phase epitaxial growth method and shaping a cap layer onto an upper clad layer. CONSTITUTION:Epitaxial growth is performed up to a current block layer 5 in succession from top of a semiconductor substrate 1, and structure in which the current block layer 5 is left by approximately 0.07 to 0.13mum by etching- working one part of the current block layer 5 to a striped shape through a lithographic technique. The striped worked and shaped trench 6 for the current path is formed completely, the whole current block layer 5 is melted back in approximately 0.15mum while the surface of an upper clad layer 4 is exposed only in the section of the trench 6 for the current path and brought into contact electrically, and a cap layer 7 and a contact layer 8 are laminated successively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a ■-M compound semiconductor laser device and a method for manufacturing the same.

[Conventional technology]

A conventional ■-Ma group compound semiconductor laser device is shown in cross-section in FIG. In the figure, 111 is an n-type GaAs semiconductor substrate F-opped with a donor such as 81 at a high concentration;
1 is a lower cladding layer of n-type AlXGa1-xAs grown on a semiconductor substrate by a method such as MO-CvD; yAs active layer 1 (2) is a lower cladding layer (21), an acceptor such as Zn which forms a double heterojunction with the active layer (31), is the upper cladding layer) 4) An n-type GaAs current blocking layer grown on the upper cladding layer.

(61 is a groove for '111 current 1st heat which is processed and formed in a stripe shape on the t current blocking layer + 51, (7) is a current blocking layer) 6) On top is the upper cladding layer 14) with m16) for the current path. (8) is a p-type AlzGa1-zAs camp layer grown by a method such as MOCVD in order to make electrical contact with the cap layer (7), and a p-type GaAs contact layer ( 91, ■11 are electrodes made entirely of materials such as AuGe or Ni e Au, which make ohmic contact with the contact layer (8) and the semiconductor substrate, respectively.◎ Next, the operation will be explained.The electrode (91, υl) to 1
When a voltage of 1 in the old direction is applied, an electric field of 11 in the PM junction including the active layer 131 is generated, and a current flows. At this time, the current selectively flows through the current passage monument (6) due to the depletion layer generated between the current blocking layer +61 and the upper cladding layer ((2)), and a local Pfr-like current flows to the active layer 131. Injection occurs, and the double heterojunction formed by the lower cladding layer +21, the active m 131 , and the upper cladding layer 1 (2) causes population inversion of the injected carriers, which causes stimulated emission of the font and causes laser oscillation. Let's do it.

Furthermore, due to the effective refractive index distribution in the lateral direction resulting from the difference in the amount of light absorbed by the upper & i active layer (3: current block Jt4+51 and the cap layer 17),
Laser oscillation characteristics with stable transverse mode and few kinks can be obtained.

[Problem to be solved by the invention]

Since the conventional semiconductor laser device is configured as described above, the manufacturing method involves forming a lower cladding layer (21), an active layer (3), an upper cladding layer 1 (2) on a semiconductor substrate Ill.
A first epitaxial growth step in which flow blocking layers (5) are sequentially laminated with 1% of the current flow blocking layer (5) is processed and formed into a stripe shape on the current blocking layer (15) to expose the cladding layer ((2)). (6) Step of forming current blocking layer 16) and ? A second epitaxial growth step occurs in which a cap layer 17) and a contact layer (8) are sequentially laminated on the groove 161 for the current path.
At the portion 610, the upper cladding Id1(2) is exposed, and in the second epitaxial growth step, in order to grow the cap layer 17+fzr, MOC! V.D.
There is a restriction that growth is not possible without using a vapor phase growth method such as Furthermore, even if the second epitaxial growth is performed using a method such as MOC! ?This is easily thought to be caused by the absorption of energy that occurs during laser operation, that is, the absorption of photons, and the increase in crystal defects associated with the generation of heat spots, which in fact leads to eccentricity and R. , these measures
The challenge was to do this.

[Means to solve the problem]

This invention was made to solve the above-mentioned problems, and it eliminates oxidation of the regrowth interface in the second epitaxial improvement step, improves crystallinity, improves authenticity, and improves manufacturing efficiency. The purpose is to improve yield and reduce costs.

[Effect]

The structure and manufacturing method of the semiconductor laser device according to the present invention is such that a current block l@+5+ is formed at the bottom of the current path $+61 formed in the current blocking layer -6) grown in the epitaxial growth process of @l above. By leaving a portion in the form of a thin film, and by forming the cap layer in the second epitaxial growth step (the growth method of 71 is melted back by liquid phase epitaxial method, etc.),
The crystallinity at the regrowth interface can be improved as described above, and reliability can be improved.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a sectional view of the semiconductor laser device, and FIG. 2 shows the manufacturing method. In the figure, the suspensions from Ill to Ill are the same as those shown in the conventional example of FIG. 8, so redundant explanation will be avoided.

(11C is a p-type A1!ZGal-ZAθ cap layer whose main surface becomes flat when grown by this method.

FIG. 2 is a diagram showing the structure after epitaxial growth of the 61st order up to the flow blocking layer +51 on the +lLI tfi semiconductor substrate 111, and this growth will hereinafter be referred to as the first shrimp growth step.

Figure 2 rb+ shows that after the shrimp growth process of the above treatment 1 is completed,
This is a diagram showing the structure after etching a part of the current block layer l1Il into a stripe shape using lithography technology.
An etchant with good etching properties, such as NH4
If a wet etchant such as oH:H@01-1:80 is used, current blocking layer 1 can be easily and reproducibly removed.
51 f! : Leave about 0.07~0.1811 m I
The groove structure shown in the b+ figure is obtained.

Figure 2 (01 is a current path layer (61) processed and formed in a stripe shape. After the formation of the current path layer (61) is completed, a cap layer (71) and a contact layer (81) are sequentially laminated by, for example, liquid phase epitaxial deposition method. This is a diagram showing the later configuration, and this growth is hereinafter referred to as the second shrimp growth process.
When growing the cap layer 17), the improved Miyama epitaxial method is used, so by optimizing the degree of supersaturation of the grown melt, current blocking is achieved by taking advantage of the characteristics of All, which has a high diffusion rate into the melt. layer + lil
The entire surface of the upper cladding layer + (2) is melted back by approximately 0.15 μm, and the surface of the upper cladding layer + (2) is formed with grooves (61
The feature is that only the zero portion is exposed and electrically contacted.

Next, the operation will be explained.

In such a semiconductor laser device, the electrode +91,
If a forward voltage is applied across al1, the laser oscillates in a stable transverse mode using the same principle as the conventional one, but with this invention, a part of the 'mi block layer +51 is left behind'.
Since the groove (8) for the flL flow path was processed, the regrowth interface 1tAlGaAs between the first shrimp growth process and the second shrimp growth process in the groove (8) for the flow path
By suppressing oxidation and performing crystal growth after partially melting back the GaA composition exposed to the atmosphere when growing the cap layer 1 during the second growth process. , the crystallinity is the same as above, and thereby it is possible to suppress the increase in defects due to reabsorption of excessive seepage energy during current-carrying operation, the accompanying crystal deterioration, and the decrease in reliability.

In the above embodiments, the conductivity type of the semiconductor substrate is shown as n-type, but it may be of the opposite conductivity type, that is, p-type, and hereinafter, the conductivity type of each semiconductor layer may also be of the opposite 4-conductivity type. good.

〔Effect of the invention〕

As described above, according to the present invention, a part of the current blocking layer is reduced to 0.
When forming the cap layer, a layer of about 0.7 to 0.18 μm is left for the current path, and when the cap layer is formed, a region left in the form of a thin film in the @ area of the groove for the current path by the melt-back method using the liquid epitaxial growth method is used. By melting back the upper cladding layer to expose the upper cladding layer and forming a cap layer on the upper cladding layer for electrical contact, regrowth with good crystallinity can be performed and the reliability can be improved. There are effects that can be achieved.

[Brief explanation of the drawing]

1 and 2 are related to one embodiment of the present invention, in which FIG. 1 is a cross-sectional view of a semiconductor laser device, FIG. 2 is a flow chart showing a method for manufacturing the semiconductor laser device, and FIG. FIG. 2 is a cross-sectional view of a conventional semiconductor laser device. In the figure, +11 is the semiconductor substrate, (21 is the lower cladding layer; 31 is the active layer, +
(2) f'j upper cladding layer, +61 is current blocking layer,
(6) Groove for current path, (71 is cap layer, (8)
is a contact layer, and 191, II) is an electrode. The same symbols in the figures indicate the same or corresponding parts.

Claims (2)

[Claims] (1) A GaAs semiconductor substrate having a first conductivity type, an Al_xGa_1_-_xAs lower cladding layer having the first conductivity type, which are sequentially laminated on the semiconductor substrate, and an Al_y
Ga_1_-_yAS active layer, A with second conductivity type
l_zGa_1_-_zAs upper cladding layer, a GaAs current blocking layer having a first conductivity type, a current path groove formed in the current blocking layer and exposing the upper cladding layer; an Al_zGa_1_-_zAs cap layer having a second conductivity type and formed to be in electrical contact with the upper cladding layer only in the current path groove and having a flat main surface; In the semiconductor laser device comprising a GaAs contact layer having a second conductivity type stacked on the cap layer, and electrodes in ohmic contact with the GaAs semiconductor substrate and the contact layer, respectively, the lower cladding layer and the active layer , the thickness of the upper cladding layer is d_1, d_2, d_3, the mixed crystal ratio of Al to Ga in each layer is x, y, z, and the thickness of the current blocking layer is d4, then 1.0 μm≦ d_1, 0.03μm≦d_2≦0.15
μm, 0.1μm≦d_3≦06μm, 0.3≦x≦
0.5, 0≦y≦0.2, 0.3≦z≦0.50.3μ
A semiconductor laser device characterized in that m≦d_4≦0.6 μm. (2) When processing and forming a current blocking layer, H_4OH:H_2O_2≠1:x or tartaric acid aqueous solution (
50wt%):H_2O_2=1:y_2SO_4:H
_2O_2:H_2O=1:Z:P or phosphoric acid:H_3
O_2=1: r10≦x≦30, 0.5≦y≦10, 0
<z≦0.5z≦P, 0<r≦0.2 etching is performed using an etchant, leaving the current blocking layer approximately 0.1 μm±0.03 μm and not exposing the upper cladding layer; Second, when growing the cap layer, the GaAs is melted back using, for example, a liquid phase epitaxial growth method, to remove the 0.000.
A method for manufacturing a semiconductor device, comprising the step of melting back only a GaAs region of about 1 μm±0.03 μm to expose the upper cladding layer during epitaxial growth.