JPH0832175A - Manufacture of semiconductor laser device - Google Patents

Abstract

PURPOSE:To provide a manufacturing method of a semiconductor laser device where the current blocking layer can be manufactured easily. CONSTITUTION:SiO2 layers 2 and 2' are formed so as to sandwich the light waveguide path formation areas R on an n-type InP substrate 1. Next, an n-type InP lad layer 3, an active layer 4, and a p-clad type InP layer 5, and a p-type InGaAs clad layer 11 are formed in order in the region R. In this case, the cross section of the multilayer structure becomes triangular. Next, the inner parts of the SiO2 layers 2 and 2' are removed, and then a p-type InP layer 6-1, an n-type InP layer 12, and a p-type InP layer 6-2 are formed in order to form a current blocking layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser device.

[0002]

2. Description of the Related Art With the progress of optical communication technology, the field of application of semiconductor lasers is rapidly expanding from backbone transmission systems to systems such as subscribers, LANs, and data links. Since semiconductor laser devices used in these fields are used in various environments and in large quantities, they are required to be excellent in environmental resistance and low in price, and active research and development are being carried out. In order to meet such requirements, selective growth using metal organic vapor phase epitaxy (MOVPE) is effective, which enables large area and uniform growth of a thin film and enables large area and uniform control of the active layer width.

A conventional method of manufacturing a semiconductor laser device will be described with reference to FIGS.

First, referring to FIG. 4A, (10)
0) orientation N-type indium phosphide (InP) substrate 1,
Approximately 2000 mm thick silicon dioxide (S
An iO ₂ ) layer is deposited, and two dielectric thin film stripes 2 and 2 ′ having a width of 10 μm and an interval of 2 μm are formed by photolithography. An area between these two dielectric thin film stripes 2 and 2 ′ is referred to as an optical waveguide forming region R.

[0005] Next, referring to FIG.
By the OVPE method, a Si-doped N-type InP cladding layer 3 having a thickness of about 1000 ° and a carrier concentration of about 1 × 10 ¹⁸ / cm ³ , an InGaAsP multiple quantum well (MQW) active layer 4 having a 1.3 μm emission wavelength composition, and a carrier concentration About 5 × 10
A Zn-doped P-type InP cladding layer 5 of ¹⁷ / cm ³ is selectively grown. Note that the film thickness is a value in the optical waveguide forming region R.

Next, referring to FIG. 5A, the inner portions of the dielectric thin film stripes 2 and 2'on the optical waveguide forming region R side are removed, and the widths of the respective dielectric thin film stripes 2 and 2'are changed. It is about 6 μm.

Next, referring to FIG. 5B, using each of the remaining dielectric thin film stripes 2 and 2'as a mask, a P type film having a film thickness of about 2 μm and a carrier concentration of about 5 × 10 ¹⁷ / cm ³ is formed. InP layer 6 and film thickness about 0.3 μm, carrier concentration about 1 ×
The P ⁺ -type InGaAsP contact layer 7 of 10 ¹⁹ / cm ³ is selectively grown.

[0008] Referring now to FIG. 6 (A), and remove the dielectric thin film stripes 2, 2 ', and推積the dielectric thin film 8 made of SiO ₂ on the entire surface again by CVD method, an optical path forming The stripes 8a having a width of about 1.5 μm on the region R are removed.

Next, referring to FIG. 6B, an electrode layer 9 is formed on an upper portion and an electrode layer 10 is formed on a lower portion, thereby completing a semiconductor laser device.

[0010]

However, the semiconductor laser device manufactured by the above-described conventional method is not suitable for use at high temperatures.
In order to drive with a low threshold value and a low current, a current block layer for preventing a leak current is required, but a method of performing a combination of photolithography and etching techniques by masking only the upper part of the optical waveguide formation region. It was complicated and difficult. Note that FIG.
2 shows a semiconductor laser device in which a current blocking layer (6, 6 ′) is formed by providing an N-type InP layer 6 ′ in the InP layer. Therefore, it is an object of the present invention to provide a method for manufacturing a semiconductor laser device that can easily manufacture a current blocking layer.

[0011]

In order to solve the above problems, the present invention first forms two dielectric thin film stripes facing each other with a narrow optical waveguide forming region on a semiconductor substrate. A first InP cladding layer in the optical waveguide formation region,
An active layer, a second InP cladding layer, and an InGaAs cladding layer are sequentially stacked and grown until the InGaAs cladding layer is covered on a surface that is difficult to grow. Next, at least the inside portions of the two dielectric thin film stripes facing each other are removed, and thereafter, a current blocking layer is grown on the entire surface of the laminated multilayer.

[0012]

According to the above means, the InP clad layer is
Although the growth rate on the (111) B plane is slower than the other plane orientations, the second InP cladding layer is grown until the cross section becomes a triangular shape composed of the (111) B side wall faces. It is difficult to stop growing. For this reason,
In order to stop the growth on the (111) B plane, the V group composition is more advantageous than that of P, so that InGaAs is formed on the uppermost layer.
Adopt clad layer. As a result, the cross-sections of the selectively grown InP cladding layer, active layer, InP cladding layer, and InGaAs cladding layer in the photoconductive path forming region have a triangular shape surrounded by (111) B plane side walls in a self-aligned manner. As a result, the current block layer is grown along the triangular side wall. That is, a semiconductor laser device is manufactured by two growths. In addition, the surface A represents a group III surface, and the surface B represents a group V surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1, 2 and 3 are sectional views showing an embodiment of a method for manufacturing a semiconductor laser device according to the present invention.

First, referring to FIG. 1A, similarly to FIG. 4A, an SiO ₂ layer having a thickness of about 2000 ° is formed on an (100) -oriented N-type InP substrate 1 by a CVD method. Then, two dielectric thin film stripes 2 and 2 ′ having a width of 10 μm and an interval of 2 μm are formed by photolithography.

Next, referring to FIG.
OVPE method, a Si-doped N-type InP clad layer 3 having a thickness of about 1000 ° and a carrier concentration of about 1 × 10 ¹⁸ / cm ³ , and an MQW of InGaAsP having a light emission wavelength of 1.3 μm.
Active layer 4, film thickness about 1.7 μm, carrier concentration about 5 × 10
Zn-doped P-type InP cladding layer 5 of ¹⁷ / cm ^3, and a thickness of about 0.2 [mu] m, selective growth of Zn-doped P-type InGaAs cladding layer 11 having a carrier concentration of about 5 × 10 ¹⁷ / cm ^3. The film thickness is a value in the photoconductive path forming region R. In this case, as shown, the cross section of the InGaAs cladding layer 11 has a triangular shape.

Next, referring to FIG. 2A, similarly to FIG. 5A, the dielectric thin film stripes 2 and 2 'are removed by removing the inner portions on the side of the optical waveguide forming region R so that each of the dielectric thin films is removed. The width of the body thin film stripes 2 and 2 ′ is about 6 μm. In this case, the dielectric thin film stripes 2 and 2 ′ are left to reduce the mesa width and reduce the capacitance to contribute to high-speed response.
All 2'may be removed.

Next, referring to FIG. 2B, using each of the remaining dielectric thin film stripes 2 and 2'as a mask, a P type film having a film thickness of about 1000 Å and a carrier concentration of about 5 × 10 ¹⁷ / cm ³ is formed. InP layer 6-1, film thickness of about 0.5 μm, carrier concentration of about 1 × 10 ¹⁸ / cm ³ N-type InP layer 12, film thickness of about 1.5
μm, P-type InP with a carrier concentration of about 5 × 10 ¹⁷ / cm ³
Layer 6-2, and film thickness about 0.3 μm, carrier concentration about 1 ×
The P ⁺ -type InGaAsP contact layer 7 of 10 ¹⁹ / cm ³ is selectively grown.

Next, referring to FIG. 3A, similarly to FIG. 6A, the dielectric thin film stripes 2 and 2 'are removed, and the dielectric thin film 8 made of SiO ₂ is again formed by the CVD method. Is deposited on the entire surface, and the width on the optical waveguide formation region R is about 1.5 μm.
In a striped shape 8a.

Next, referring to FIG. 3B, similarly to FIG. 6B, an electrode layer 9 is formed on the upper part and an electrode layer 10 is formed on the lower part, thereby completing the semiconductor laser device. .

When the semiconductor laser device according to the present invention was evaluated at a cavity length of 300 μm, at room temperature, the threshold current was 8 mA on average, the standard deviation was 0.2 mA, and the slope efficiency was 0.2 on average.
It was 35 W / A and the standard deviation was 0.04 W / A. Also,
At 85 ° C., the threshold current was 20 mA on average and the slope efficiency was 0.2 W / A. This result is improved as compared with the semiconductor laser device according to the conventional method. By using the present invention, a low threshold voltage and a low current drive at a high temperature can be achieved.

[0021]

As described above, according to the present invention, 2
Since the semiconductor laser device having the current blocking layer is manufactured by the single growth, the semiconductor laser device can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 2 is a sectional view illustrating a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 3 is a cross-sectional view showing a method of manufacturing a semiconductor laser device according to the present invention.

FIG. 4 is a cross-sectional view showing a conventional method for manufacturing a semiconductor laser device.

FIG. 5 is a cross-sectional view showing a conventional method for manufacturing a semiconductor laser device.

FIG. 6 is a cross-sectional view showing a method for manufacturing a conventional semiconductor laser device.

FIG. 7 is a cross-sectional view showing a conventional semiconductor laser device having a current block layer formed thereon.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... N-type InP substrate 2, 2 '... Dielectric thin film stripe 3 ... N-type InP clad layer 4 ... MQW active layer 5 ... P-type InP clad layer 6, 6-1 and 6-2 ... P-type InP layer 7 P ⁺ type InGaAsP contact layer 8 Dielectric thin film 9, 10 Electrode layer 11 P type InGaAs clad layer 12 N type InP layer R Optical waveguide formation region 6-1, 12, 6-2 Current block layer

Claims (6)

[Claims] 1. A stripe forming step of forming two opposing dielectric thin film stripes (2, 2 ′) on a semiconductor substrate (1) by narrowing an optical waveguide forming region (R), and after the stripe forming step. A first InP cladding layer (3), an active layer (4), a second InP cladding layer (5), and an InGaAs cladding layer (11) are sequentially grown in the optical waveguide forming region, and the InGaAs cladding layer is formed. A first growing step of growing the dielectric thin film until it is covered with a hard-to-grow surface, and a stripe removing step of removing at least an inner portion of the two dielectric thin film stripes opposite to each other after the first growing step; A second growth step of growing a current block layer (6-1, 12, 6-2) on the entire surface of the stacked multilayer after the removal step. Law. 2. The method for manufacturing a semiconductor laser device according to claim 1, wherein the surface that is hard to grow is a (111) B surface. 3. The InP layer of a first conductivity type (6-1), an InP layer of a second conductivity type opposite to the first conductivity type (12), and the second growth step includes: In of the first conductivity type
2. The method for manufacturing a semiconductor laser device according to claim 1, wherein the P layers (6-2) are sequentially grown. 4. A stripe forming step of forming two opposing dielectric thin film stripes (2, 2 ′) on an N-type InP substrate (1) while narrowing an optical waveguide forming region (R); After that, an N-type InP cladding layer (3), an InGaAs PMQW layer (4), a P-type InP cladding layer (5), and a P-type InGaAs cladding layer (11)
Are successively grown, the P-type InGaAs cladding layer is grown until its (111) B surface is covered, and the cross-sectional shape of the stack is triangular. After the triangular forming step, A stripe removing step of removing at least inner portions of the two dielectric thin film stripes facing each other; and after the stripe removing step, a current blocking layer (6-1, 12, 6-2) is formed on the entire surface of the laminated multilayer. Growing the semiconductor laser device. 5. The InP layer of a first conductivity type (6-1), an InP layer of a second conductivity type opposite to the first conductivity type, and the second growth step. In of the first conductivity type
The method for manufacturing a semiconductor laser device according to claim 4, wherein the P layers (6-2) are sequentially grown. 6. A semiconductor substrate (1), and a first InP clad layer (3), an active layer (4), and a second InP clad, which are laminated on an optical waveguide forming region (R) of the semiconductor substrate. Semiconductor comprising a layered structure (5) and an InGaAs cladding layer (11) having a triangular cross-section, and current blocking layers (6-1, 12, 6-1) grown on both sides of the triangular cross-sectioned laminated structure. Laser device.