JPS6190489A - Semiconductor laser device and manufacture thereof - Google Patents

Abstract

PURPOSE:To enable laser beams and carriers to be effectively confined in both directions vertical to and parallel with the active layer, by a method wherein the refractive index of clad layers sandwiching the active layer is decreased with distances from the center of the active region. CONSTITUTION:The active layer 7 and a multilayer thin film including a double- hetero structure are formed on a substrate 5 having the groove part, and the refractive index of a clad layer 6 sandwiching the active layer 7 decreases with distances from the center of an active region 11. For example, on the substrate 5 having the groove part, an n type Ga1-xAlxAs clad layer 6 is epitaxially grown 1.5mum at the flat part, the Ga1-yAlyAs active layer 7 0.05mum, a p type Ga1-zAlzAs clad layer 8 1.2mum at the flat part, and an n type GaAs current block layer 9 0.5mum. At this time, the mixed crystal ratio in the layer of the n type Ga1-xAlxAs clad layer 6 is made smaller toward the active layer; therefore, this device is produced so that the refractive index may be larger toward the active layer. Thereafter, a p type GaAs region 10 is formed by Zn diffusion, and ohmic electrodes 13 and 12 are prepared on the p side and n side, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor laser device used as a light source for various electronic devices and optical devices, and a method for manufacturing the same.

Conventional Structures and Problems The important performances required of semiconductor lasers as coherent light sources for electronic and optical equipment include low current operation and single-transverse mode oscillation. In order to achieve these, it is necessary to effectively confine the laser light near the active region where the laser light propagates, and to suppress its spread so as to concentrate the current flowing through the laser element. A laser with a convex structure is usually called a striped semiconductor laser.

A relatively simple striping method uses only current constriction. Specifically, planar semiconductor lasers that have been subjected to proton irradiation, those that have been subjected to Zn diffusion, those that have an insulating film such as an oxide film formed, and those that have a current confinement region created inside by crystal growth etc. Can be mentioned. However, in these methods, the confinement of the laser light is weak, and although the current can spread, it cannot be said that the carriers are effectively confined within the active layer.

Also, an example of a green laser (gray desode indenox laser) that effectively confines light and carriers by changing the refractive index and energy gap in the cladding layers that sandwich the active layer of a conventional planar semiconductor laser, achieving low current operation. However, it was insufficient in terms of light confinement in the direction parallel to the active layer.

OBJECTS OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a semiconductor laser device having a structure that effectively confines laser light and carriers in both directions perpendicular and parallel to the active layer, and a method for manufacturing the same.

Structure of the Invention To achieve this object, the semiconductor laser device of the present invention includes a multilayer thin film including an active layer and a double heterostructure provided on a substrate having a groove, and a refractive index of the cladding layer sandwiching the active layer. , is configured such that it decreases as it moves away from the center of the active region.

With this configuration, a strong current narrowing stripe is provided inside, and the laser light can be effectively confined within the active region by changing the refractive index and the carriers by changing the energy gap, resulting in low current operation, single-transverse mode oscillation, Oscillation with high differential quantum efficiency is realized.

Furthermore, the method for manufacturing a semiconductor laser device of the present invention is characterized by including a step of forming a cladding layer on a substrate having a groove by metal organic vapor phase epitaxial growth.

DESCRIPTION OF EMBODIMENTS An embodiment of the semiconductor laser device of the present invention will be specifically described with reference to the drawings.

As an example, an n-type GaAg substrate (carrier concentration ~1018 (approximately ff1-3)) is used as the conductive substrate.As shown in FIG. Width 6μm with a pitch of 250μm in the horizontal direction
Stripes are formed using a photoresist film, and grooves with a depth of 2 μm are created by chemical etching. FIG. 2 shows a cross-sectional shape of the substrate 5 having a groove. On this substrate 6, as shown in FIG.
The As cladding layer 6 has a thickness of 1.5 μm on the flat part, Ha,
yAeyAs active layer 7 (0≦y(x, y(z)
0.05 μm.

The p-type Ga+-zAA'z" cladding layer 8 is 1.
A 2plJn type GaAs current i-stop layer 9 was epitaxially grown with 0.5 strands. However, at this time, n-type G"1-XA
The mixed crystal ratio in the lxmuS cladding layer 6 was made to decrease as it got closer to the active layer, and therefore the refractive index was made to increase as it got closer to the active layer. The refractive index profile had its origin at 0 shown in FIG. 3, and the 3'RI7LIX direction was set as shown in FIG. 4 or FIG. 5, respectively. An example in which the mixed crystal ratio in the normal cladding layer is not changed and therefore the refractive index is not changed is shown in FIG. Compared to FIG. 6, the profiles in FIGS. 4 and 6 confine carriers in the yRlyL and x directions in the active layer.

Not only that, laser light can also be effectively confined. In addition, to give an example of the conditions for crystal growth by the MOCVD method, the growth temperature is 770'C, the growth rate is 8 μm/hour, the molar ratio of the Group Ⅰ element to the Group 1 element is 60, and the total gas flow rate is 6.
(1/min.) Thereafter, as shown in FIG. 3, Zn was diffused to form a p-type GaAs region 10.Ohmic electrodes 10 and 12 were formed on the p-side and n-side, respectively.

When current was injected, single-transverse mode oscillation occurred at a low threshold of 25 mA to 30 mA. A high value of 80% or more was also obtained for the outer quantum differential efficiency on both sides of the resonator.

Experiments have demonstrated that by changing the mixed crystal ratio in the cladding layer, it is possible to give the energy gap and refractive index a profile that is effective for confining carriers and laser light.

Further, the p-type GaA/As cladding layer 8 on the active layer 7 may also have a similar refractive index change.

In this embodiment, GaAs-based and GaAlAs-based semiconductor lasers have been described, but the present invention can be similarly applied to semiconductor lasers made of compound semiconductors including InP-based and other multi-component mixed crystals. Other LPIC methods or MBE methods may be used in combination with the crystal growth method.

Effects of the Invention As described above, the semiconductor laser device and the manufacturing method thereof of the present invention provide a semiconductor laser device that oscillates in a single transverse mode with high efficiency and low current operation, and its practical effects are remarkable.

[Brief explanation of drawings]

1, 2, and 3 are diagrams showing the process of manufacturing the semiconductor laser device described in this example, and FIGS. 4 and 5 are diagrams showing the refraction in the cladding layer in this example. FIG. 6 is a diagram showing a refractive index profile of a conventional semiconductor laser device. 1...GaAs substrate (ool) surface, 2...
...Stripe, 3...(oll) side, 4...
...(Qll) plane, 6...n-type GaAS substrate, 6...n-type Ga, -Aj7xAs cladding layer, 7...Ga, , A%As Active layer, 8...
...p-type Ga1-2AlzAS cladding layer, 9-.
- N-type GaAs current blocking layer, 1o...p-type GaAs region by Zn diffusion, 11... active region, 12... n-side ohmic electrode, 13...・
...p-side ohmic electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A multilayer thin film including an active layer and a double heterostructure is formed on a substrate having a groove, and the refractive index of the cladding layer sandwiching the active layer decreases as it moves away from the center of the active region. Semiconductor laser device. (2) A method for manufacturing a semiconductor laser device, comprising the step of forming a cladding layer on a substrate having a groove by metal organic vapor phase epitaxial growth.