JP2626570B2 - Method for manufacturing semiconductor laser device - Google Patents

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 advancement of optical communication technology, the application field of semiconductor lasers has been 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 satisfy such requirements, selective growth using metal organic chemical vapor deposition (MOVPE), which enables large area and uniform growth of a thin film and enables large area and uniform control of the active layer width, is effective.

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

First, referring to FIG. 4A, (10)
0) On an N-type indium phosphide (InP) substrate 1 having an orientation,
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 dielectric thin film stripes 2 and 2 ′ are removed from the inner portion on the optical waveguide forming region R side, and the width of each of the dielectric thin film stripes 2 and 2 ′ is reduced. It is about 6 μm.

Referring to FIG. 5B, a P-type film having a thickness of about 2 μm and a carrier concentration of about 5 × 10 ¹⁷ / cm ³ is formed using the remaining dielectric thin film stripes 2 and 2 ′ as a mask. InP layer 6, thickness of about 0.3 μm, carrier concentration of about 1 ×
A 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 at a low threshold value and a low current, a current block layer for preventing a leak current is required, but a method of combining photolithography and etching techniques by masking only the upper portion of the optical wave path forming region And it was complicated and difficult. FIG.
1 shows a semiconductor laser device in which a current blocking layer (6, 6 ′) is formed by providing an N-type InP layer 6 ′ in an InP layer. Accordingly, it is an object of the present invention to provide a method of manufacturing a semiconductor laser device that can easily manufacture a current blocking layer.

[0011]

According to the present invention, two opposing dielectric thin film stripes are first formed on a semiconductor substrate by narrowing an optical waveguide forming region on the 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-mentioned 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]

1, 2 and 3 are sectional views showing one 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, 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.
2 'may be entirely removed.

Next, referring to FIG. 2B, using the remaining dielectric thin film stripes 2 and 2 'as a mask, a P-type film having a thickness of about 1000 ° and a carrier concentration of about 5 × 10 ¹⁷ / cm ³ is used. InP layer 6-1, N-type InP layer 12 having a thickness of about 0.5 μm and a carrier concentration of about 1 × 10 ¹⁸ / cm ³ , a thickness of about 1.5
μm, P-type InP with a carrier concentration of about 5 × 10 ¹⁷ / cm ³
Layer 6-2, thickness about 0.3 μm, carrier concentration about 1 ×
A 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.
35 W / A, standard deviation 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 the 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 sectional view illustrating a method for manufacturing a semiconductor laser device according to the present invention.

FIG. 4 is a 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 conventional method for manufacturing a 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 board | substrate 2, 2 '... Dielectric thin film stripe 3 ... N-type InP cladding layer 4 ... MQW active layer 5 ... P-type InP cladding 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 cladding layer 12 ... N-type InP layer R ... optical waveguide forming region 6-1, 12,6-2 ... current block layer

Claims (6)

(57) [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 on which growth is difficult 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), a first InP cladding layer (3), an active layer (4), and a second InP cladding laminated on an optical waveguide forming region (R) of the semiconductor substrate. A semiconductor comprising: a layered structure of a triangular sectional shape of a layer (5) and an InGaAs cladding layer (11); and current blocking layers (6-1, 12, 6-1) grown on both sides of the triangular sectional shape laminated structure. Laser element.