JPH0521907A - Manufacture of semiconductor laser element - Google Patents

Abstract

PURPOSE:To simplify a manufacturing process, to improve the heat characteristics of a manufactured element and to obtain a stable transverse mode by enabling manufacture by two-time growth. CONSTITUTION:An N-type AlGaInP lower clad layer 21, a GaInP active layer 22, a P-type AlGaInP carrier confinement layer 23, a P-type GaInP etching stop layer 24 and an N-type GaAs current block layer 25 are grown successively onto an N-type GaAs substrate 11 through an MOVPE method and an MBE method in a first growth process. The current block layer 25 is etched selectively to form a stripe groove 32. The semiconductor substrate is treated with ammonium sulfide, and irradiated with As molecular beams in an MBE device and thermally cleaned. A P-type AlGaAs upper clad layer 41 and a P-type GaAs cap layer 42 are laminated successively on the surface of the semiconductor substrate through the MBE method in a second growth process.

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. Specifically, the present invention relates to AlGaI
The present invention relates to a method for manufacturing an nP-based visible light semiconductor laser device.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing a conventional AlGaInP-based visible light semiconductor laser device. This semiconductor laser device 51 is manufactured by using a metal organic chemical vapor deposition method (MOVPE), and further, through three crystal growth steps (hereinafter, simply referred to as growth steps) (for example, ELECTRONICS).
LETTERS, 1987 Vol.23 No.18 P.938-939).

That is, the manufacturing sequence will be described with reference to FIG. 2. First, in the first growth step, the GaAs substrate 52 is formed.
N-GaAs buffer layer 53, n- (Al _0.4 G
a _0.6) 0 _.5 In _0.5 P lower cladding layer 54, Ga _0.5 In
_0.5 P active layer _{55, p- (Al 0. 4Ga 0.6} ) 0.5 In 0.5
P inner clad layer 56, p-Ga _0.5 In _0.5 P etching stop layer 57, p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5
The P outer cladding layer 58 and the p-GaAs cap layer 59 are sequentially grown. After that, a SiO ₂ mask (not shown) is formed in the center of the upper surface of the cap layer 59, and the cap layer 59 and the outer cladding layer 58 are selectively chemically etched to the etching stop layer 57 through the SiO ₂ mask.
Are etched into a mesa shape to form a ridge portion 60. After forming the ridge portion 60, in the second growth step, the n-GaAs current blocking layer 61 is formed outside the ridge portion 60.
Grow. Then, after removing the SiO ₂ mask on the ridge portion 60, in the third growth step, the p-GaAs cap layer 62 is grown again on the cap layer 59 and the current blocking layer 61. After this, the cap layer 62
Forming a p-side electrode 63 of Ti / Pt / Au on
An n-side electrode 64 is formed on the lower surface of the GaAs substrate 52.

[0004]

Therefore, in the method of manufacturing the semiconductor laser device having the above structure, the step of crystal growth on the wafer is required three times, which complicates the manufacturing process. There is a defect that micro defects easily occur in the crystal due to thermal history.

Further, in conventional visible light semiconductor laser devices, AlGaI is formed in the p-side (inner and outer) cladding layers.
Although nP is used, AlGaInP has a large specific resistance and a small thermal conductivity, which is disadvantageous in thermal characteristics and has a problem that the maximum oscillation temperature is small (Tmax≈70 ° C.).

Further, the conventional index-guided laser device has three elements.
There is a problem that the element characteristics such as FFPθ _// (far-field image in the direction parallel to the active layer) are large because the ridge width is poorly controlled by etching and the ridge width is poorly controlled.

The present invention has been made in view of the above-mentioned drawbacks of the conventional examples. The purpose of the present invention is to make it possible to manufacture by double growth, simplify the manufacturing process, and have excellent thermal characteristics. Moreover, it is another object of the present invention to provide a method for manufacturing a visible light semiconductor laser device capable of obtaining a stable transverse mode.

[0008]

In the method for manufacturing a semiconductor laser device according to the present invention, in the first growth step, a current block layer is formed above the active layer, and then a waveguide for the current block layer is formed. After removing the region corresponding to the part by etching, and then performing ammonium sulfide treatment, the second
It is characterized in that the AlGaAs cladding layer is formed above the current blocking layer by the molecular beam epitaxial growth method in the growth step of the second time.

[0009]

In the semiconductor laser device manufactured by the method of the present invention, a current is injected into the active layer through the removal region (stripe groove) of the current block layer, and laser light is emitted from the end face of the active layer. It Moreover, since the current block layer is removed by etching in the region corresponding to the waveguide formation portion after the first growth step, the cladding layer is formed on the current block layer by the second growth step. A semiconductor laser device can be manufactured by the growth process, and the growth process can be reduced by one from the conventional three-time growth method, which simplifies the manufacturing process. Moreover, by reducing the number of growth steps, it is possible to reduce crystal defects due to thermal history and the like.

Further, since the AlGaAs clad layer is used, the specific resistance is small and the thermal conductivity is large as compared with the clad layer made of AlGaInP in the conventional example. As a result, the thermal resistance is reduced and the maximum oscillation temperature is increased. Tmax is improved.

Furthermore, since the ammonium sulfide treatment is applied after etching the current blocking layer, no oxide is present on the surface, and then the second crystal growth can be performed by the molecular beam epitaxial growth method.
Moreover, since the molecular beam epitaxial growth method is used in the second growth step, it is excellent in stability and reproducibility such as FFPθ _// .

[0012]

1 (a) to 1 (c) are cross-sectional views showing a method of manufacturing a refractive index guided AlGaInP visible light semiconductor laser device 1 according to an embodiment of the present invention.
FIG. 3C is a sectional view showing the manufactured semiconductor laser device 1.

FIG. 1 shows a method of manufacturing this semiconductor laser device 1.
A description will be given according to (a) to (c). First, in the first growth step, n-type (Al _0.7 Ga _0.3 ) is formed on the n-type GaAs substrate 11 by metalorganic vapor phase epitaxy (MOVPE) method or molecular beam epitaxial growth (MBE) method in the growth apparatus. ) _0.5 In _0.5 P lower cladding layer 21, GaInP active layer 22, p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P carrier confinement layer 2
3. An etching stopper layer 24 made of p-type GaInP (layer thickness 50Å) and a current blocking layer (light absorption layer) 25 made of n-type GaAs are sequentially grown. As a result, FIG. 1 (a)
As shown in, the first growth layer 20 composed of five layers is laminated on the n-type GaAs substrate 11.

An n-type GaAs substrate 11 is formed as shown in FIG.
After taking out the semiconductor substrate on which the first growth layer 20 is formed from the growth apparatus, a photoresist 31 is applied on the current blocking layer 25, and an area corresponding to the waveguide formation portion is formed through the exposure and development processes. Of the photoresist 31 is peeled off, and the region of the current block layer 25 other than the region corresponding to the waveguide forming portion is covered with the photoresist 31. Further, hot phosphoric acid (etchant) is used to selectively etch from the current blocking layer 25 to the interface with the etching stop layer 24 using the photoresist 31 as a mask to form stripe grooves 32 on the surface of the first growth layer 20 (FIG. 1 (b)). The photoresist 31 on the surface is removed after this.

Then, the semiconductor substrate from which the photoresist 31 has been removed is immersed in an ammonium sulfide solution for 5 minutes, washed with pure water, and then dried with nitrogen. By subjecting the semiconductor substrate to ammonium sulfide treatment, the oxide on the surface is replaced with sulfide.

After that, the semiconductor substrate is delivered into an MBE device (not shown) and mounted in a predetermined position. After mounting on the MBE device, the semiconductor substrate is heated at about 500 ° C. while irradiating the semiconductor substrate with As molecular beams to perform thermal cleaning. Here, since the semiconductor substrate has been subjected to ammonium sulfide treatment and has no oxide film on its surface, thermal cleaning can be performed at a low temperature.

Then, the second growth step is carried out in the MBE apparatus. That is, by the MBE method,
An upper clad layer 41 made of p-type Al _0.8 Ga _0.2 As and a cap layer 42 made of p-type GaAs are formed on the surface of the semiconductor substrate (current blocking layer 25 and etching stop layer 24).
Are sequentially laminated, and the upper clad layer 4 is formed on the first growth layer 20.
The second growth layer 40 composed of 1 and the cap layer 42 is formed.

Finally, the p-side electrode 5 is formed on the cap layer 42.
1 is formed on the lower surface of the n-type GaAs substrate 11 and the n-side electrode 5
2 to form a semiconductor laser device 1 as shown in FIG.

As a result, an electrically good layer having no optical absorption between the upper cladding layer 41 and the etching stopper layer 24 can be obtained at the striped groove 32 portion of the current blocking layer 25, Current is efficiently injected from the p-side electrode 51 to the active layer 22.

The upper clad layer 41 is made of AlGaAs.
Since it is formed by, the specific resistance is small, the thermal conductivity is good, and the thermal resistance is small. Therefore, the heat generated inside is transferred to the p-side electrode 51 and radiated from the p-side electrode 51. Therefore, the episide down mounting can effectively dissipate the internal heat and prevent the temperature rise of the element.

Further, since the refractive index guiding type structure is formed by the selective etching and the MBE method, a stable transverse mode characteristic can be obtained, and variations in element characteristics such as FFPθ _// are reduced. ..

[0022]

According to the present invention, a semiconductor laser device can be manufactured by two growth steps, and the manufacturing process is simplified by reducing the number of growth steps. Furthermore, since the number of growth steps is reduced, crystal defects due to thermal history can be reduced.

Further, since the clad layer made of AlGaAs is provided, the specific resistance is small and the thermal conductivity is large. As a result, the thermal resistance is reduced and the maximum oscillation temperature Tmax can be improved.

Furthermore, since the ammonium sulfide treatment is applied after etching the current blocking layer, no oxide is present on the surface, and then the second crystal growth can be performed by the molecular beam epitaxial growth method.
Moreover, since the molecular beam epitaxial method is used in the second growth step, a stable transverse mode can be obtained,
It is possible to manufacture semiconductor laser devices with excellent stability and reproducibility such as FFPθ _// .

[Brief description of drawings]

1A, 1B, and 1C are cross-sectional views showing a method for manufacturing a semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a conventional AlGaInP-based visible light semiconductor laser device.

[Explanation of symbols]

 20 First Growth Layer 22 Active Layer 24 Etch Stop Layer 25 Current Block Layer 32 Stripe Groove 40 Second Growth Layer 41 Upper Cladding Layer 42 Cap Layer

Claims (1)

Claim: What is claimed is: 1. In the first growth step, a current block layer is formed above the active layer, and then a region of the current block layer corresponding to the waveguide formation portion is removed by etching. Then, after performing the ammonium sulfide treatment, in the second growth step, an AlGaAs cladding layer is formed above the current blocking layer by a molecular beam epitaxial growth method.