JPS6014485A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce the oscillation threshold value and to upgrade the external differentiated quantum efficiency by a method wherein the bottom surface of a groove between two ridges on a substrate, which has the two ridges standing straight in parallel to each other, is located lower than the stepped surfaces on both the outsides of the ridges; a P-N junction face, which is parallel to the main plane of the substrate, is formed on the lower sides of the ridges and the stepped surfaces in such a condition as to be discontinued by the groove; and a double hetero structure including an active layer is formed on the ridges. CONSTITUTION:A first current constricting layer 9 of a P type Ga1-xAlxAs, a second current constricting layer 10 of an N type Ga1-xAlxAs and a third curret constricting layer 11 of a P type Ga1-xAlxAs are continuously grown on the surface of an N type GaAs substrate 1 in an order of the current constricting layers 9, 10 and 11 by a liquid- phase epitaxial method. Two ridges are formed on the surface of a wafer, which finished this first-time growth, toward the <011> direction holding a groove between them by performing an etching. An N type Ga1-xAlxAs clad layer 2 of the first layer, a non-dopped Ga1-yAlyAs active layer 3 of the second layer, a P type Ga1-xAlxAs clad layer 4 of the third layer and a P type GaAs electrode forming layer 5 of the fourth layer are continuously grown on the surface of the substrate 1 formed with the two ridges by an epitaxial method again.

Description

[Detailed Description of the Invention] [Object of the Invention] The present invention is based on the TBS (T-cho rLRidgeBtbhjtr) which has already been developed by the present inventors.
The present invention relates to an improvement of a semiconductor laser device having a structure. In recent years, there has been an increasing demand for high-output semiconductor laser devices that emit fundamental transverse mode oscillation in a wide range of fields, such as those used to fill optical disk files and laser printers, and the TR8 type semiconductor laser device meets this demand. be.

FIG. 1 shows a conventional TR8 type semiconductor laser device using an r+4 substrate, in which two glue holes are formed in parallel and upright on a substrate 1, and each layer 2, 4, 5 including an active layer 3 is formed on them. Continuous growth and diffusion of zinc over the crystal surface for current injection 8
After this, electrodes 6.7 are formed on both the upper and lower surfaces. Due to the anisotropy of crystal growth, this structure allows the growth on the ridge to be suppressed compared to the side surfaces of the ridge, so that an extremely thin active layer can be formed on the ridge with good reproducibility. As the active layer becomes thinner, the confinement coefficient of light in the active layer becomes smaller, so the light seeps into the cladding layer to a large extent, and the light that seeps into the first cladding layer 2 does not reach the top of the hole other than the active part. Since it is absorbed by the substrate, it is confined in the groove between the ridges, and stable fundamental transverse mode oscillation can be achieved.

However, the conventional structure shown in FIG. 1 has the following problems. (1) The current injected from the zinc diffusion region 8 flows not only to the trench where excavation is performed but also to the drilled part other than the trench, so these currents do not cause losses but are effective to the trench. inhibits the injection of current. (2)
Since there is a limit to the controllability of thermally diffusing zinc to an arbitrary depth with good reproducibility in the form of stripes, the diffusion front may not reach the third cladding layer 4.
Alternatively, the light may reach the active layer 3, which may cause a decrease in the oscillation rate. An object of the present invention is to provide a TR8 type semiconductor laser device having a novel structure in which these problems are solved.

[Structure of the Invention] In the semiconductor laser device of the present invention, the bottom surface of the groove between the ridges of the semiconductor substrate having two glue holes standing upright in parallel is also below the stepped surfaces on both outer sides of the two glue holes. At least one layer parallel to the main plane of the semiconductor substrate is provided below the two glue holes and the stepped surfaces on both sides thereof.
A double heterostructure including an active layer is formed on the two pn junctions, the two pn junctions being interrupted by the grooves, and the two grooves.

The configuration of the present invention will be explained with reference to FIGS. 2 and 6.

A first current confinement layer 9 of P-type G (Z1-x, p, 1xAs) is formed on the surface of the rL-type GαAJ' substrate 1 by a liquid phase epitaxial method to a thickness of 0.31 iyn and an n-type G (Zl-xAlx
The second current narrowing layer 10 of As has a thickness of 0.3 μ'' and is of P type Gα.
The sixth current confinement layer 11 of 1-xAtxAs has a thickness of 1.4μ.
Continuous growth is performed in the order of m (Fig. 3 α).

On the surface of the wafer after this first growth, <01
1. Two glue holes each having a width of 20 μm are formed by etching in the > direction with a groove having a width of 4 μm in between. The depth of the groove between the ridges is about 2.2 μm, and the bottom reaches the square substrate 1. On the other hand, the height of the outside of the ridge is approximately 1.1 μm, and the third current narrowing layer 11 remains on the surface (Fig. 3b).
. On the surface of the substrate 10 on which the ridge has been formed in this way, the first layer of L-type Gα1-xAl xA is again epitaxially applied.
The thickness of the s-cladding layer 2 on the ridge is approximately 0.2 μm.
.

The second layer non-doped Gα1-yllyAz active layer 3 is made of GaA,? Similarly, the electrode forming layer 5 is continuously grown to a thickness of about 05 .mu.m, respectively j (FIG. 5C). In the above embodiment, -M=0.43 and y=008. A p-side electrode metal is deposited on the fourth electrode forming layer 5 and alloyed to form a p-side ohmic electrode 6. On the substrate side, an n-side electrode metal is deposited and alloyed. 7) After forming the 4All,%-mic electrode 7, the semiconductor wafer of the present invention shown in FIG. 2 is obtained.

[Effects of the Invention] Since the semiconductor laser device of the present invention has the above configuration, the P-ru junction is brought into a reverse bias state by the action of the current confinement layer formed in the first epitaxial growth.
Block current.

For this purpose, the current fl, injected from the growth surface is intensively injected into the active layer above the trench where oscillation occurs. As a result, the oscillation threshold can be lowered and the external differential quantum efficiency can be improved. As a result of the experiment, it was confirmed that the oscillation threshold is approximately 30 mA and the external differential quantum efficiency is approximately 70 coefficients, which provides a lower threshold and higher efficiency than the conventional TR8 type half-9 body laser. It was done.

Moreover, 7-! of the present invention! The structure allows current to pass between the ridges.
'↓' is limited to 4 parts, so there is no need for zinc diffusion for the '1u flow injection, which is required in conventional TFiS semiconductor lasers, so there is no reduction in the oscillation rate due to variations in the search for zinc diffusion. In addition, the process after epitaxial growth can be carried out with ease.

Although the present invention has been described above using an rL-type substrate, it goes without saying that the present invention can be implemented in the same manner using a p-type substrate, and the same effects will be obtained.

[Brief Description of the Drawings] Figure 1: Cross-sectional view of a conventional TR8 type semiconductor laser device No. 2V2 Cross-sectional view of a TR8 type semiconductor laser device of the present invention No. 6N: Manufacture of the TPh Kanhayabusa conductor laser device of the present invention In the process diagram, α and Jc indicate each step. 1... IL type σαA, s' substrate, 2... Le type GIZ
1. A 3 oxid layer, 6... non-doped G (Xi
-9AlyhS active layer, 4-=p-type G (Zl-xAl
, ycAs cladding layer, 5... rL 弗aay raL
Pole forming layer...P-type ohmic electrode, 7=-n ohmic electrode, 8...-zinc diffusion region, 9''-P-type Gl-xAlxy first current confinement layer 10 ・-n g'i
G(Zl-xAlxp-s second current narrow 9 layer 11”・
Pi! , 1 () (Zi-, y: A1. y: As 3rd current narrow Y layer fang 1 Figure 2 Figure 3 ([

Claims (1)

[Claims] The bottom surface of the groove between the ridges of the semiconductor substrate having two glue holes standing upright in parallel is also below the stepped surfaces on both outer sides of the two glue holes, and the bottom surface of the groove between the ridges of the semiconductor substrate has two glue holes standing upright in parallel. On the lower side of the surface, at least one p-type bonding surface parallel to the main plane of the semiconductor substrate is interrupted by the groove!
1. A semiconductor laser device characterized in that a double heterostructure including an active layer is formed on the two glue holes.