JPH0353581A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser which is small in astigmatism by a method wherein a mesa stripe is formed using an insulating film as a mask for selective growth so as to enable both the ends of the mask to extend much from the edge of the mesa stripe. CONSTITUTION:An N-type (Al0.6Ga0.4)0.5In0.5P layer 2, an active layer 3, a clad layer 4, and a cap layer 5 are successively formed on an N-type GaAs substrate 1 through a low pressure MOVPE method. A stripe-like SiO2 mask 9 7mum in width is formed through photolithography, the cap layer 5 is selectively etched into a mesa shape 3mum in width, in succession the layers under the layer 5 are etched. Thereafter, leaving the mask as it is, a second growth is carried out to form an N-type GaAs layer 6. After the mask is removed, a third growth is executed to form a buried layer 7 and a contact layer 8. Lastly, a P and an N electrodes are formed, and the substrate 1 is so cleaved as to make a cavity 250mum in length and separated into chips.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention provides an AIG aIn that records in a single transverse mode.
This article relates to a method for manufacturing a P-based semiconductor laser device. (Prior art) Recently, A that oscillates in a single transverse mode is formed by crystal growth using metal organic pyrolysis (hereinafter abbreviated as MOVPE).
As an IGaInP-based semiconductor laser device, #4n as shown in Fig. 3 has been reported (Extended
Abstracts of the 18th Con
ference on Solid State De
vices and Materials, Tokyo0
．． 1988. D.D. 153-156). This jfR
Traditionally, kashi is made using the following process. That is, in the first growth, n-type (AlosG) is grown on the n-type GaAs substrate 1.
ao. < ) o. s I no. s P cladding layer 2
, Gao. s I no. s P active layer 3, p type (AI
(1.GEho.*) o. s I no. S P cladding layers 4 are sequentially formed. Thereafter, mesa stripes are formed using photolithography using the Sins as a mask. Then, with the S lot mask on, a second growth was performed, and the etched area was grown as n-type Ga.
Embed with As layer 6. Next, the SIO 2 mask is removed, and a P-type GaAs contact layer 8 is grown in a third step so that an electrode can be formed on the entire p-side surface. In such an S structure, current is blocked by the n-type GaAs layer 6 and is injected only into the mesa stripe portion.
In addition, when etching to form a mesa stripe, the thickness of the p-type cladding layer other than the first mesa stripe is etched to a thickness insufficient for confining light, so the n-type Ga
In a certain portion of the As layer 6, light is absorbed by the n-type GaAs layer 6 and is guided only to the mesa stripe portion. In this way, in this I structure, the current confinement R side and the optical waveguide mechanism are built at the same time. (Problems to be Solved by the Invention) In the canopy shown in Figure 3 obtained by the conventional manufacturing method described above, since light absorption is used to stabilize the mode, the wavefront of light is delayed on both sides of the mesa stripe. The problem is that astigmatism becomes large. The fourteenth aspect of the present invention is to solve the above-mentioned problems and to
AIGa with transverse mode control horizontal construction with small astigmatism
An object of the present invention is to provide a method for manufacturing an InP-based semiconductor laser device. (Means for Solving the Problems) In order to solve the above-mentioned problems, in the method for manufacturing a semiconductor laser device according to the present invention, on a first conductivity type GaAs substrate,
It consists of an active layer and a cladding layer sandwiching this active layer and having a refractive index lower than that of the active layer (Alm Ga+-g
) o. s I no. a step of forming a double hetero II m of s P (0≦x≦1) system, a step of forming a GaAs-based semiconductor layer of a second conductivity type on the double hetero structure, and a step of forming a GaAs-based semiconductor layer of the second conductivity type. A. A step of forming a striped insulator layer on the s-based semiconductor layer, and etching the GaAs-based semiconductor layer of the second conductivity type using the striped insulator layer as a mask. etching so that the distance between the edge of the GaAs-based semiconductor layer and the edge of the mask of the striped insulator layer is greater than the sum of the thicknesses of the second conductivity type GaAs-based semiconductor layer and the upper cladding layer; , etching the lower cladding layer of the double heterostructure halfway to form a mesa-like stripe, and using the stripe-like insulator layer as a selective mask using an organometallic pyrolysis vapor phase or lengthening method. A process of forming GaAs or GaInP of the first conductivity type in a portion other than the mesa-shaped stripes, and removing the stripe-shaped insulator layer to form GaAs or GaInP of the second conductivity type and having a lower refractive index than the active layer (AIK Ga+ -x ) o.s I no
．． s Including the step of shaping the P layer. (Function) In the case of the AIGaInP system, growth is difficult with the liquid phase growth method, and selective growth using Si 0 2 as a mask is difficult even with the MOVPE method. Therefore, in the present invention, after forming a double heterostructure, an insulating film is used as a mask for selective growth.
The ends of this mask are shaped like mesa stripes that protrude greatly. By doing this, the source gas cannot reach the parts that are in the shadow of the mask, and the current confinement layer can be formed in a self-aligned manner only in parts other than the mesa. Then, after removing the mask, the refractive index is smaller than that of the active layer (A l
zGa+-*) o. s I no. If the sP layer is formed, both ends of the active layer are also filled with this layer, and a real refraction type laser can be realized, and a laser with small valve point aberration can be obtained. (Example) Next, an example of the present invention will be explained using drawings. FIG. 1 is a sectional view of a laser chip showing one embodiment of a semiconductor laser device obtained by the present invention, and FIGS. 2(a) to (d)
1 is a manufacturing process diagram showing an embodiment of a laser device according to the present invention. First, in the first low-pressure MOVPE growth, n-type GaA
On the s-substrate 1, an n-type (A I 0.6 Gao.<)
o. s I no. s P layer 2, Gao. s I no
% P active 3, P type (A I o.h G & o.
< ) o. s I no. The growth conditions for sequentially forming the sP cladding layer 4 and the p-type GaAs cap layer 5 are, for example, a temperature of 700°C, a pressure of 70'l"orr, and a V/1 1
1=200, total flow rate of carrier gas (H1) 151/
Let it be min. The raw material is trimethylindium (
'I'MI:(CHs)3In)}ethylgallium(TEG:(CIHs)xGa),
}'Remethylaluminum (TMA: (CHs
) s A 1 ), arsine (AsH, ), phosphine (PH3), n-type dopant: hydrogen selenide (H-
tSe), P-type dopant: dimethyl zinc (D
MZ:(CH3) x Zn) is used.
A striped SiO 2 mask 9 with a width of 7 μm is formed on the elongated wafer by photophosphorography (FIG. 2<a)). Next, using this Sto2 mask 9, the p-type GaAs'r layer 5 is selectively etched into a mesa shape until it has a width of, for example, 3 μm, and subsequently,
n-type (A I o. G ao. < ) o. sI
no. s Pl2, Gao. s I no. qP
Active layer 3. p-type (AI o.a G&o4) o. s
I no. s P clad M4 to n type (A lo.
6 G ao. 4) o. s I n. ．． Etch the P layer 2 to the middle (Fig. 2(b)). Here, p-type G
a A s 'r guy 7 layer 5 etching width 3μm
is the distance between the edge of the p-type GaAs cap layer 5 after etching and the edge of the striped SiOzWA 9 mask,
The thickness is selected to be larger than the sum of the thicknesses of the p-type GaAs cap layer 5 and the upper cladding layer 4. Afterwards, depressurize MOVPH while wearing the S i O 2 mask 9.
A second elongation process is performed to form an n-type GaAs layer 6 (FIG. 2(c)). After removing the S I O 2 mask 9, a third growth is performed by low pressure MOVPE to form a p-type (AI o. 6 Gao. 4) o. s I n
o. sPj! A p-type GaAs contact layer 8 is formed. Finally, both P + n electrodes are formed and separated into individual chips with a cavity length of 250 μm. A cross-sectional view of the semiconductor laser device obtained through the above steps is shown in FIG. 1, and it has been experimentally confirmed that the astigmatism of this semiconductor laser device is 2 μm or less. This value corresponds to the astigmatism of the conventional semiconductor laser device of 5 to 1
It can be seen that there is a significant improvement compared to 0 μm. In the embodiments described above, the active layer is a specific set of precepts, but
As long as these satisfy the requirements of the present invention, the active layer may have a composition or quantum well that satisfies the oscillation wavelength requirements for the laser device being manufactured, and the cladding layer structure may be optically optical with respect to the active layer structure to be used. It is sufficient to choose a composition that can sufficiently confine carriers. Furthermore, depending on the characteristics required for the laser device, the cladding layer can be made more multilayered, such as by using a SCHIl structure. (Effects of the Invention) As explained above, based on the method of manufacturing a semiconductor laser device according to the present invention, a semiconductor laser with small astigmatism can be obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a semiconductor laser device obtained by the present invention, FIGS. 2(a) to (d) are cross-sectional views showing the manufacturing process of the present invention, and FIG. FIG. 2 is a cross-sectional view showing an example of a body laser device. 1 --- n-type GaAs substrate, 2-n type (AI., aG ao. *) o. s
I no. g P cladding layer, 3...G ao. s
I no. s P active layer, 4 ・p type (AI0.4Ga
o,) o. s I no. i P cladding layer, 5-P
type GaAs cap layer, 6-n type GaAs layer, 7 ・p
Type (A lo.a G ao.a ) o. s I
no. s P buried layer, 8... p-type GaAs contact layer, 9... st021 model,

Claims (1)

[Claims] On a first conductivity type GaAs substrate, an active layer and a cladding layer sandwiching the active layer and having a lower refractive index than the active layer are formed (Al_xGa_1_-_x)_0_. ＿51
n_0_. a step of forming a _5P (0≦x≦1)-based double heterostructure, a step of forming a second conductivity type GaAs-based semiconductor layer on the double heterostructure, and a step of forming the second conductivity type GaAs-based semiconductor layer a step of forming a striped insulator layer on the second conductivity type GaAs-based semiconductor layer, and etching the second conductivity type GaAs-based semiconductor layer using the striped insulator layer as a mask; The distance between the edge and the edge of the mask of the striped insulator layer is the second
A process of etching the conductive type GaAs-based semiconductor layer so that the thickness is greater than the sum of the thicknesses of the upper cladding layer, and etching this to the middle of the lower cladding layer of the double heterostructure to form mesa-shaped stripes. The process of
Using the striped insulator layer as a selective mask, the first conductivity type GaAs or GaI is grown by metal organic pyrolysis vapor phase epitaxy.
A step of forming nP in a part other than the mesa-shaped stripes, and removing the striped insulating layer to form nP with a second conductivity type and a lower refractive index than the active layer (Al_xGa_1_-_x
)_0_. _5In_0_. A method for manufacturing a semiconductor laser device, comprising the step of forming a _5P layer.