JPH0637390A - Semiconductor laser and its manufacture - Google Patents

Abstract

PURPOSE:To provide a stable lateral mode control type high output semiconductor laser device. CONSTITUTION:High resistance regions 6a made of the same material as the second cladding layer 6 of a single lateral mode control type semiconductor laser crystal structure are formed on the ridge sides of the second cladding layer 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device structure using a compound semiconductor and a manufacturing method thereof, and more particularly to an AlGaInP semiconductor laser device structure and manufacturing method.

[0002]

2. Description of the Related Art In recent years, AlGaInP semiconductor lasers have been promising as a light source in the field of optical information processing because they have an oscillation wavelength (680 nm) in the visible light region, and have been developed in various places.

3 (a) to 3 (c) show a manufacturing process diagram of a conventional AlGaInP semiconductor laser in which a lateral mode type is controlled.
In the laser device manufactured by this step, in the vicinity of the active layer 4, a second P-type clad layer 12 having a larger forbidden band width than the active layer 4 is provided in parallel with the current confinement layer having a smaller forbidden band width than the active layer 4. It has a structure sandwiched by 15, and obtains a single mode by controlling the transverse mode. The laser device having this structure is manufactured in the order of (a), (b), and (c) of FIG. FIG. 3A shows a step of crystal-growing a double hetero structure. The n-type GaAs buffer layer 2 and the N-type are formed on the GaAs substrate 1.
AlGaInP clad layer 3, active layer 4, first P-type AlGaInP
Cladding layer 5, second P-type cladding layer 6, P-type GaAs layer 7
Are sequentially laminated. Next, as shown in FIG. 3B, the P-type GaAs layer 7 and the second P-type GaAs layer 7 are formed using the SiO ₂ film 8 as an etching mask.
The type AlGaInP clad layer 6 is partially etched to form a mesa structure. Next, as shown in FIG. 3C, the n-type GaAs current confinement layer 9 is selectively grown by the second growth, and then,
The SiO ₂ film 8 is removed and a P-type GaAs cap layer 10 is laminated on the entire surface to complete a semiconductor laser device.

[0004]

However, in this step, when manufacturing a semiconductor laser controlled in a single transverse mode, that is, when manufacturing a semiconductor laser device having a narrow stripe, the process shown in FIG. As shown, n-type GaAs
An interface level due to re-growth exists at the interface between the current confinement layer 9 and the second P-type AlGaInP cladding layer 6 formed in the mesa stripe shape. Although its concentration is 10 ¹² cm ^-2 ,
When the semiconductor laser is operated at a high output, the lattice defects forming the interface state serve as nuclei to induce defects in the crystal forming the semiconductor laser. As a result, the semiconductor laser is rapidly deteriorated, and it is difficult to extend the life of the semiconductor laser. The interface state can be reduced by optimizing the growth conditions at the time of regrowth, but it is impossible to make the interface level below 10 ¹² cm ^-2 .

The present invention solves the above problems, and provides a device structure of a lateral mode controlled semiconductor laser which is easy to manufacture and has a low threshold oscillation, and a manufacturing method thereof.

[0006]

The present invention includes a double hetero structure including an N-type cladding layer, an active layer and a first P-type cladding layer on a crystal substrate, and further comprises the first P-type cladding layer.
A semiconductor laser device having a mesa-stripe-shaped second clad layer on a mold clad layer, and a side surface of the second clad layer formed in the mesa-stripe shape has high resistance. Is.

In order to fabricate the above-mentioned semiconductor laser device structure, an N-type clad layer, an active layer, a first P-type clad layer and a second clad layer are formed on a crystal substrate. A step of sequentially laminating, a step of etching and removing in a mesa stripe shape having a mask on the second cladding layer, and a semiconductor crystal processed in a mesa stripe shape having the mask in a hydrogen atmosphere in a plasma or hydrogen atmosphere. The present invention provides a method for manufacturing a semiconductor laser device, which is characterized by the step of performing heat treatment.

[0008]

According to the device structure of the present invention, even if an interface level is formed at the interface between the clad layer formed in the mesa stripe shape and the current confinement layer at the time of re-growth, the region where the interface level is formed is formed. Since the vicinity of is a high resistance region, even when the semiconductor laser operates at high output, no current is injected into the vicinity of the interface state, so that deterioration of the semiconductor laser caused by interface defects is avoided. Further, by using the device structure of the present invention, the injection area of carriers into the active layer can be made small, so that single transverse mode control can be easily performed at a low threshold value.

Further, in the manufacturing method of the present invention, the element structure of the semiconductor laser described above can be easily manufactured by performing heat treatment in a hydrogen atmosphere in plasma or in a hydrogen atmosphere. Moreover, the thickness of the high resistance region formed on the side surface of the mesa stripe of the second niclad layer can be controlled, and the device can be easily designed. Further, in the manufacturing method of the present invention, at the regrowth interface of the p-type GaAs layer in which current actually flows, a mask is provided at the regrowth interface when performing heat treatment in the hydrogen atmosphere in plasma or in the hydrogen atmosphere. It can be manufactured in a state in which the initial resistance of the crystal is preserved without increasing the resistance.

[0010]

The details of the present invention will be described with reference to the embodiments shown in the drawings.

FIG. 1 is a sectional view showing a schematic structure of a semiconductor laser according to an embodiment of the present invention. In the figure, 1 is n-type GaAs
A substrate, 2 is an n-type GaAs buffer layer (1 × 10 ¹⁸ c
m ⁻³ , 0.5 μm), 3 is an N-type AlGaInP clad layer (1
× 10 ¹⁸ cm ⁻³ , 1.0 μm), 4 is a GaInP active layer (0.06 μm), 5 is a first P-type AlGaInP clad layer (4 × 10 ¹⁷ cm ⁻³ , 0.25 μm), and 9 is n. Type GaAs current confinement layer (2 × 10 ¹⁸ cm ⁻³ , 0.5 μm), 6 is the second P type AlGaInP cladding layer (7 × 10 ¹⁷ cm ⁻³ , 0.6)
μm), 7 and 10 are p-type GaAs cap layers (2 × 10
¹⁸ cm ⁻³ , 2 μm). Here, the composition of the N-type AlGaInP clad layer 3, the first P-type AlGaInP clad layer 5, and the second P-type AlGaInP clad layer 6 is Al: Ga: In =
It is 0.35: 0.15: 0.5. Further, 5a is a high resistance region formed in a region having regrowth on the first cladding layer, and 6a is a high resistance region formed in a region having regrowth on the second cladding layer.

When the above structure is used, the second AlGaIn
The stripe width of the P-clad layer 6 was set to 3 μm. At that time, 2 μm in the region near the P-type GaInP layer 6
The confinement of the transverse mode is facilitated, the confinement of the current is improved, and a low threshold element can be obtained.

According to the device structure of the present invention, even if an interface level is formed at the interface between the cladding layer 6 formed in the mesa stripe shape and the current confinement layer 9 during regrowth, the interface level is formed. Since the high resistance region 6a is in the vicinity of this region, no current is injected into the vicinity of the interface state even when the semiconductor laser is operating at high power, so that the deterioration of the semiconductor laser caused by the interface defect is avoided. Actually, an interface level of about 10 ¹² cm ^-2 is formed at the interface between the side surface of the mesa stripe of the second cladding layer 6, which is the regrown interface, and the current confinement layer 9, and the interface level is set to 10 ¹² cm ^-2 or less. Things are technically impossible. The semiconductor laser does not induce defects in the crystal during high-power operation, and as a result, it is possible to extend the life of the semiconductor laser during high-power operation.

2 (a) and 2 (b) are sectional views showing a method of manufacturing a semiconductor laser and a schematic structure according to an embodiment of the present invention. As shown in FIG. 2A, by the MOVPE method,
On n-type GaAs substrate 1, n-type GaAs buffer layer 2 and N-type Al
GaInP clad layer 3, active layer 4, first P-type AlGaInP clad layer 5, second P-type AlGaInP clad layer 6, p-type GaAs
Layer 7 is grown sequentially to form a double heterostructure. Next, a SiO ₂ film 11 is deposited in stripes on the p-type GaAs layer 7, and the p-type GaAs layer 7 and the second P-type AlGaInP are deposited.
SiO ₂ film 11 in which the clad layer 6 is processed into the stripe shape
Is used as a mask and is removed by etching to form a mesa-shaped DH structure substrate. Next, as shown in FIG. 2B, plasma or heat treatment is performed on the mesa-shaped DH structure substrate in a hydrogen atmosphere. By performing plasma or heat treatment in a hydrogen atmosphere, hydrogen atoms are injected into the regrown surface of the mesa-shaped DH structure substrate. As a result, hydrogen atoms are injected into the crystals of the regrown surfaces of the first P-type clad layer 5 and the second P-type clad layer 6 to inactivate impurity atoms, and thus the high resistance regions 5a and 6a. Is formed.

When plasma is performed, the mesa-shaped DH structure substrate is subjected to 3 times in a hydrogen atmosphere at a pressure of 0.2 Torr.
It heated at 00 degreeC and it performed under the electric field of 100 eV. At this time, hydrogen atoms have a penetration depth of 500 A, and a high resistance occurs in the range of 500 A.

Next, using the SiO ₂ film 8 as a mask, the n-type GaAs layer 9 is selectively grown by regrowth, the SiO ₂ film 8 is removed, and then the P-type GaAs cap layer 10 is sequentially grown to form a semiconductor laser device. Make the structure. PH on the regrown surface
By introducing ₃ , it is possible to prevent surface damage due to temperature rise, and the region where a current flows maintains a low resistance state because the SiO ₂ film 8 serves as a mask for hydrogen atom implantation.

Although GaInP is used for the active layer 4 in this embodiment, it is also possible to use an AlGaInP layer or a multiple quantum well structure, and AlInP is used for the second P-type cladding layer.
It goes without saying that it is also possible to use layers. Also,
In this embodiment, plasma is used as the hydrogen injection method, but it goes without saying that other methods can be used.

[0018]

As described above, according to the present invention, the stripe width of the second P-type AlGaInP cladding layer in the vicinity of the active layer can be narrowed, and as a result, the current can be narrowed in a narrow width. Thus, a laser element controlled in transverse mode with a low threshold value can be easily manufactured.

Further, since the device structure of the semiconductor laser of the present invention in which the transverse mode is controlled can be easily manufactured, and the region serving as the current path at the time of regrowth is not affected by hydrogen implantation. The density of defects generated at the regrowth interface is reduced, and an AlGaInP layer having good characteristics can be grown.
The life of the element can be extended.

[Brief description of drawings]

FIG. 1 is a sectional view showing a device structure of a semiconductor laser according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of a semiconductor laser according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of a conventional semiconductor laser.

[Explanation of symbols]

1 n-type GaAs substrate 2 n-type GaAs buffer layer 3 n-type clad layer 4 active layer 5 first P-type clad layer 5a high resistance region 6 second P-type clad layer 6a high resistance region 7 p-type GaAs layer 8 SiO ₂ film 9 n-type current confinement layer 10 p-type GaAs layer 15 hydrogen injection

Claims (2)

[Claims] 1. A double hetero structure comprising an N-type clad layer, an active layer and a first P-type clad layer on a crystal substrate, and a mesa stripe-shaped structure on the first P-type clad layer. A semiconductor laser device having a second clad layer, wherein a side surface of the second clad layer formed in the mesa stripe shape has a high resistance. 2. A step of sequentially laminating an N-type clad layer, an active layer, a first P-type clad layer and a second clad layer on a crystal substrate, and on the second clad layer. A step of having a mask on and etching away in a mesa stripe shape,
A method of manufacturing a semiconductor laser device, comprising the step of subjecting a semiconductor crystal processed into a mesa stripe shape having the mask to a heat treatment in a hydrogen atmosphere in plasma or in a hydrogen atmosphere.