JPS5941885A - Semiconductor laser element - Google Patents

Abstract

PURPOSE:To eliminate the adverse effects caused by a current blocking layer wherein Te is doped and to impart long life operation characteristics, by adding a GaAs buffer layer on a Te doped N<+> GaAs current blocking layer. CONSTITUTION:On a Zn doped P<+> GaAs substrate 21, a current blocking layer 22 comprising Te doped N<+> GaAs is grown by a liquid phase epitaxial growing method. Then a buffer layer 23 comprising undoped GaAs or Si doped N<-> GaAs is grown. Thereafter, a stripe shaped groove 24 is etched from the buffer layer 23 to the substrate 21. Then, a first clad layer 25, an active layer 26, a second clad layer 27, and a cap layer 28 are sequentially deposited by the liquid phase epitaxial growing method again. Thereafter a P type electrode 29 and an N type electrode 30 are evaporated and formed. Then the wafer is divided with the stripe groove 24 as the center, and the end surface of a resonator is formed by a cleaving method.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a semiconductor laser device, and particularly to a C31S (Ch=annele) in which a channel groove for current confinement is formed in a substrate.
d 5ubstrate Inner 5tri
pe) Concerning the element structure of a laser.

<Prior art> As a semiconductor laser device in which a channel groove is formed in a substrate, a C3P (Chan-neled laser diode) as shown in FIG.
2. Description of the Related Art A laser device having a five-layer planar structure is known. This semiconductor laser element is. -G
The epitaxial growth surface of the aAs substrate 1 is etched to form stripe-shaped grooves 2, and the n-GaA
After growing the tAs cladding layer 3 so that its top surface is flat, a GaAs active layer 4, a p-GaAtAs cladding layer 5, and an n-GaAs current blocking layer 6 are sequentially laminated. By diffusing Zn etc., p −Q
The aAs diffusion layer 7 is formed as a current path, and the n-Ga
An n-side electrode 8 is formed on the back surface of the As substrate 1, and a p-side electrode 9 is formed on the p+- diffusion layer 7. In the active layer 4, the laser operation is performed directly above the groove 2, and the thin n-cladding layer 3
Since a waveguide mechanism is constructed in which the light from the active layer 4 seeps into the n-GaAs substrate 1 at the part in contact with the n-GaAs substrate 1, complete single-mode laser oscillation can be performed both vertically and horizontally within an appropriate drive current range. can. However, as shown by the arrows in FIG. 1, the semiconductor laser device having the above structure causes an increase in the current that restricts the current path width in the vicinity of the active layer.

FIG. 2 is a configuration diagram showing a semiconductor laser device in which an internal stripe structure is introduced in order to suppress reactive current in view of the above problems.

This semiconductor laser device has the same waveguide structure as the C8P structure shown in FIG. 1, but uses a p-GaAs substrate 11 instead of the n-type substrate 1, and
An As current blocking layer 12 is interposed.

Due to the presence of the current blocking layer 12, the current passing width corresponding to the groove 2 from which the current blocking layer 12 has been removed is regulated at both sides of the channel, as shown by the arrow in the figure, and the current does not spread in the lateral direction. Increase in reactive current is suppressed. Such a structure is called a C31S structure.

However, the current blocking layer 12 is made of n+-GaAs (with a thickness of approximately 0 .6 μm), a multilayer crystal for laser oscillation, that is, a p-GaAtAS cladding layer 3', an active layer 4, an n-GaAtAs cladding layer 5', and an n-Ga
In order to grow the As cap layer 13, the influence of Te appears on this multilayer crystal layer, and many defects such as lamella patterns and prechibitates occur. Generally, when forming an evitaginal growth layer on a Te doped layer, a buffer layer is interposed to achieve crystal recovery.
In the C5IS structure as shown in the figure, the p-
Since only the GaAtAs cladding layer 3' can be grown, if this cladding layer 3' is also used as the buffer layer, it will not be possible to sufficiently recover the adverse effects of Te by the time it reaches the active layer 4 due to the layer thickness. If the crystallinity of the active layer 4 is inhibited, deterioration of device characteristics and operating life cannot be prevented.

<Object of the Invention> In view of the above-mentioned problems, the present invention provides a novel and useful method that eliminates the adverse effects caused by Te-doped current blocking layers and provides long-life operating characteristics by making full use of technical means. C
An object of the present invention is to provide a semiconductor laser element 1 with an 8IS structure.

<Example> Hereinafter, the present invention will be explained in detail according to an example with reference to the drawings.

FIG. 3 is a block diagram of a semiconductor C-buzzer element showing one embodiment of the present invention. 4(A), 4(B), 4(C), and 4(D) are manufacturing process diagrams of the semiconductor laser device shown in FIG. 3.

The semiconductor laser device of this embodiment has a GaAs buffer layer 23 on a Te-doped current-GaAs current blocking layer 22.
is added. By depositing the GaAs buffer layer 23, the layer thickness for crystal recovery is approximately doubled, so the influence on the active layer 26 is greatly alleviated.

Furthermore, if the conductivity type of the buffer layer 23 is undoped or n-type, the current blocking ability and the C8P effect can be obtained in the same manner as in the prior art. Therefore, in addition to vertical and horizontal single moat oscillation, the life characteristics are greatly improved.

The manufacturing process will be explained below.

Zn-doped p with carrier concentration of lx1019-3
A current blocking layer 22 made of Te-doped n4-GaAs having a carrier concentration of 5X10'8-3 is formed on a +-Gal+ substrate 21 by liquid phase epitaxial growth.
．． Furthermore, a buffer layer (crystalline recovery layer) 23 made of undoped GaAs or Si-doped n-Gan As having a carrier concentration of 1Xl0173 is 7 μm1.
It is grown to a thickness of μm (FIG. 4(A)). Thereafter, a striped groove (channel) 24 is etched from the buffer layer 23 to the GaAs substrate 21 by a photo process (FIG. 4(B)).

After forming stripe grooves 24 with a pinch of 300 μm, Zn-doped p
Ga□, 2A70. The first cladding 25 made of BAs is undoped with a layer thickness of 0.25 μm and 0.38 Ga.
The active layer 26 is made of 0.62P0.78ASO,22 with a layer thickness of 0.1 μm, Te-doped n-Gao, 2At, 8
The second cladding layer 27 made of As has a layer thickness of 1.0 μm,
Cap layers 28 made of Te-doped n-GaAs are deposited one after another to a thickness of 2 μm (FIG. 4(C)).
o Next, after forming the p-type electrode 29 and the n-type electrode 30 by vapor deposition, the wafer is divided into 300i, A semiconductor laser device as shown in FIG. 5 is a block diagram of a semiconductor laser device showing another embodiment of the present invention. Also, Figure 6 (AXBXC) (D) is the 5th
FIG. 3 is a manufacturing process diagram of the semiconductor laser device shown in the figure.

In the semiconductor laser device of this example, the thickness of the buffer layer is increased in order to further improve the effect of crystallinity recovery. By increasing the thickness of the n-GaAs buffer layer, the depth of the channel groove exceeds 1 μm,
Therefore, the layer thickness of the p-GaAtAs first cladding layer is set to 0.2
When the thickness is set to about 5 μm, it becomes impossible to completely fill the groove with this cladding layer. It is not possible to increase the cladding layer thickness from the viewpoint of single mode oscillation, so 1
By further interposing one p-GaAs buffer layer on the 1-GaA^ buffer layer and partially filling the groove with this p-GaAs buffer layer, the top of the cladding layer deposited thereon is flattened. - If such a structure is used, the current confinement effect will be slightly inferior, but the original C8P effect will not change, and even longer life is expected.

The manufacturing process will be explained below.

On a Zn-doped p-GaAs substrate 31 having a carrier concentration of 1XlO193, a current blocking layer 32 made of Te-doped n"'-GaAs having a carrier concentration of 5X10183 and 0η is formed with a thickness of 0 by the liquid phase epitaxy growth method. .7 μm1 additionally undoped GaAs or Si doped n with carrier concentration lXl0173
- A first buffer layer 33 made of GaAs is grown to a thickness of 0.4 μm. After that, from the buffer layer 33, QaAs
The striped grooves 34 reaching the substrate 31 have a depth of 1.5 μm.
Processed using photoetching technology. The reason why the depth of the groove 34 is made as deep as 1.5 μm is to eliminate non-conductivity in the channel due to variations in layer thickness during liquid phase growth, and also because of the p-GaAs buffer layer 33 introduced in the subsequent second growth. This is to ensure that the channels (grooves) are filled appropriately.

After forming this striped groove 34 with a pinch of 300 μm, Zn-doped p-Ga is grown again by epitaxial growth.
The second buffer layer 35 made of As has a layer thickness of 0.1 μm (
At this time, the layer thickness at the center of the channel is 0.7 to 08 μm.
), Zn h' -n p Ga
. , 2 A t o, the first cladding/1i36 made of sAs is undoped with a layer thickness o of 25 μm.
Ga P As is 0.38 0.6
2 0.78 0.22 with a layer thickness o of 1 μm, Te-doped n-Gao, 2A7c), B
The second cladding layer 38 made of As has a layer thickness of 1 μm and is made of Te.
The cab layer 39 made of doped n+-GaAs has a layer thickness of 2μ.
m, and each is grown sequentially. Next, a P-type electrode 4o and an n-type electrode 41 are formed by vapor deposition, and the wafer is divided into 300 μm wide pieces centering on the stripe groove 34, and resonator end faces are formed by the arm-opening method to produce a semiconductor laser device. In this embodiment, the buffer layer thickness is approximately 0.7 μm, which is approximately twice that of the embodiment shown in FIG.

<Effects of the Invention> According to the present invention, even when a Te-doped n-type layer is interposed around the channel trench as a current blocking layer, the Te-doped layer does not have an adverse effect on the active layer. An active layer with good crystallinity can be formed, and device characteristics and lifetime characteristics can be maintained well.

[Brief explanation of the drawing]

FIG. 4 is a block diagram of a conventional C8P structure semiconductor laser device. FIG. 2 is a block diagram of a C5IS structure semiconductor laser device, which is the basis of the present invention. FIG. 3 is a configuration diagram of a semiconductor laser device showing one embodiment of the present invention. 4(A), (B), (C), and (D) are manufacturing process diagrams of the semiconductor laser device shown in FIG. 3. FIG. 5 is a configuration diagram of a semiconductor laser device showing another embodiment of the present invention. 6(A), 6(B), 6(C), and 6(D) are manufacturing process diagrams of the semiconductor laser device shown in FIG. 5. 21.31...p+-GaAs substrate 22.32-current blocking layer 23.33...n-GaAs buffer layer 26, . 37-...Active layer 35...p-G
aAs buffer 7 layers ′ Agent Patent attorney Aihiko Fukushi (and 2 others) Figure 5

Claims (1)

[Claims] 1. Depositing a Te-doped n-type current blocking layer on a P-type substrate,
1. A semiconductor laser device in which a striped channel trench is opened as a current path, and a buffer layer for restoring crystallinity is superimposed on the current blocking layer.