JPS59117287A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To block a current, which flows into the outside of a mesa region almost completely, by utilizing the increasing effect of a crystal growing speed in a grooves, providing a semiconductor layer in the vicinity of an active layer with good reproducibility, and making it possible to avoid the lamination of the semiconductor layer on the upper part of the mesa region. CONSTITUTION:On an N type GaAs substrate 1, an N type Al0.4Ga0.6As layer 2, an Al0.05Ga0.95As layer 3, which is to become an active layer, a P type Al0.4Ga0.6As-layer 4, and a P type GaAs layer 5 are formed. Mesa etching is performed so as to reach the substrate 1, and a stripe shaped mesa region having an active region is formed. Two grooves reaching the substrate 1 are provided. A P-type Al0.35Ga0.65As layer 6, an N type Al0.35Ga0.65As layer 7, and a P-type Al0.35Ga0.65As layer 12 are sequentially formed so as to surround the side surface of the mesa. Then the crystal growing speed in the grooves is expedited, and the crystal is not laminated on the upper part of the mesa. The crystal can be grown only on the side surface. Thereafter, a P-type GaAs layer 13 is formed on the entire surface of the crystal including the upper part of the mesa. Then, a P-type impurity diffused layer 8, a P-type ohmic electrode 10, and an N-type ohmic electrode 11 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a buried semiconductor laser with current confinement.

The structure shown in FIG. 1 has been considered as a structure of a buried semiconductor laser so far. That is, in FIG. 1, 1 is an n-type GaAs substrate, and 2 is an n-type Alo4Ga substrate.
O,6AB layer, 3 is Aloo5Ga6. g5As layer,
4 is pmAlo4Gao6AS layer, 5 is p-type GaAs layer, 6 is p''m A7 o, ss Ga o, eBAs layer X7 is n-type, e O, 35 Ga O, 65 As layer, 8
is a p-type impurity diffusion layer, 9 is 8i0. 6 represents an n-type ohmic electrode, and 11 represents an n-type ohmic electrode.

In this structure, a forward voltage is applied to the n-type ohmic electrode (to) and the n-type ohmic electrode (lυ), and AA!o
, o sGaO,95AS layer (3) by injecting current to cause emission recombination to enable laser operation,
The p-type A7o4Ga (1,6AS layer (6) blocks current flowing outside the mesa region, and efficiently injects current into the mesa region to increase the efficiency of laser oscillation.

However, in order to manufacture such a semiconductor laser, it is necessary to form a mesa part including the layer 2.3.4.5 by chemical etching or the like, and then surround this mesa part by a second crystal growth process. p-type AlO, 35GaO, 65AS
Ji 6 and n-type A7o, 35GaO, 65As layer 7
need to grow sequentially. However, in the second crystal growth process, p-type Al o35Ga o65As65A
As shown in Figure 1, the s-long surface is AlO,0, which becomes the active layer.
It is difficult to precisely match the position of the 5Ga0.95ASJ layer 3, and the layer 6 is often formed up to the upper part of the mesa side surface as shown in FIG. This is Al
In order to achieve a slow crystal growth rate and good buried growth on the GaAs mesa side surface, a highly supersaturated solution must be used. by.

Therefore, in the case of the structure shown in Figure 2, p-type A4 g
, 35 oao65As layer 6 and p-type GaAs layer 5 tend to be electrically at the same potential, and current easily flows to areas other than the mesa region, making laser oscillation impossible.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the conventional semiconductor laser described above and to construct a current confinement type buried structure semiconductor laser device with good reproducibility.

The semiconductor laser of the present invention includes a multilayer semiconductor layer having an active layer and a semiconductor layer sandwiching the active layer from above and below and having a larger forbidden band width than the active layer on a semiconductor substrate, and a multilayer semiconductor layer including the active layer. comprising a mesa region sandwiched between two band-shaped grooves penetrating to reach the semiconductor substrate, and not laminated on top of the mesa region including an active layer sandwiched by the band-shaped grooves,
At least one semiconductor layer having a forbidden band width larger than that of the semiconductor substrate is provided to be laminated on the side portions and other regions, and the same semiconductor layer as the previous semiconductor substrate is provided so as to cover the entire area including the upper part of the mesa region. It is characterized by having a semiconductor layer having a larger forbidden band width than that.

Embodiments according to the present invention will be described below with reference to the drawings. FIG. 3 shows an embodiment according to the present invention. In the diagram,
The same parts as those explained in connection with FIG. 1 are indicated by the same symbols.

First, in the first crystal growth step, n-type AX 6.4 Ga (1,6
As m (21, Alo, osGao, which becomes the active layer)
g5As layer (3), p-type AJ O, 4Ga g, 6As
A p-type GaAs layer (5) is formed. The thickness of each layer is 1.5 μm, 0.1 μm, and 1.5 μm, respectively.
m, 017 μm. Thereafter, when the conventional structure is formed, mesa etching is performed until the GaAs substrate (1) is reached by a similar etching process to form a band-shaped mesa region having an active region. The difference from the conventional structure is that two grooves reaching the GaAs substrate (1) are provided in the mesa etching. Here, the mesa width (Fig. 3 Wl
) is 1~3 ltm, groove width (W2) is 5~1
It was set to 0 μm.

Next, in a second crystal growth step, p-type AlO, 35Ga (1,65A
s layer (6) 1n type A4,350a (1,65AS hJ
AV)SJ) type A76.35GaO,65AS)@(
12) are sequentially formed. Here, the width is about 5-10μ
The crystal growth rate in the groove of m is about three times faster than the crystal growth rate in a flat surface because the crystal growth process from the sides of the groove is also added.

Therefore, in the conventional method, the side surfaces of the mesa are buried with a very high degree of supersaturation, resulting in poor controllability of the layer thickness, but with the present invention, buried growth can be easily achieved without increasing the degree of supersaturation to an extremely high degree. It has become possible. Again, the mesa width (
Wl) Since it is narrow at 1 to 3 μm, it is not laminated on top of it,
Crystal growth is possible only on the sides. This is because As in the growth solution is depleted in that direction due to the growth process on the mesa sides, and when the mesa width is 3 μm or less, the crystal growth on the mesa sides is always dominant, and there is no layering on the top of the mesa. was found experimentally.

Thereafter, a p-type GaAs layer (13) is formed on the entire surface of the crystal including the upper part of the mesa, and a p-type impurity diffusion layer 13), a p-type ohmic electrode (↓・, and an n-type ohmic electrode (1υ) are formed to form the present invention. Such a semiconductor laser is formed.

In this structure, the p-type Allo35Gao,t;sAs layer (
6) and n-type 'j' 0.3+Ga (1,65AS layer). p-type AA with high resistance to ?0,35()ao
, 65As layer (6) and n-type AA! oa5 oa O
, 65As layer (7) can be omitted.

Also, p-type AA located at the bottom of the side of the mesa! o35Ga(
The 1,65As layer (6) is a GaAs substrate (1)J:
Since the forbidden band width is large, the diffusion potential difference at this junction surface can be increased. Therefore, almost completely blocking current flowing to areas other than the mesa region can be easily achieved. Furthermore, because of the current blocking effect of this mesa side surface, there is no need to form a Sin film for current confinement as in the conventional structure, and the P
Room temperature oscillation threshold current lQ with only type ohmic electrodes
This enabled efficient laser oscillation at mA.

Furthermore, in this structure, n-type Alo, 35Ga (1,6
5AS layer (p-type GaAs layer α with higher thermal conductivity than power)
is formed over the entire surface, the heat dissipation characteristics are improved compared to the conventional structure, and laser oscillation can be performed even at an ambient temperature of 140°C.

Furthermore, since the element surface is formed flat, uniform fusion can be achieved when fixing it to the heat sink, and the application of stress due to thermal distortion can be avoided, making it possible to provide a highly reliable semiconductor laser. It is something.

As described above, the present invention eliminates the drawbacks of conventional semiconductor lasers, blocks current flowing outside the mesa region, enables efficient laser operation, and improves heat dissipation characteristics and reliability. Excellent semiconductor lasers can be formed with good reproducibility.

[Brief explanation of the drawing]

1 and 2 are structural cross-sectional views of a conventional buried semiconductor laser, and FIG. 3 is a structural cross-sectional view of an embodiment of the present invention. In each figure, 1: n-type GaAs substrate 2: n-type AJo, 4 GaO, 6AS f-3: A
-lO05Ga(,,g5As)i4:p type! 'J
(,4Ga (,,6As)g15:p-type GaAs layer 6:p-type AA!g,35Ga 0065AS layer 7:n
Type MO, 35Ga O, 65AS 48: p-type impurity diffusion layer 9: Sin2 layer 10: p-type ohmic electrode 11: n-type ohmic electrode 12: p-type 1' J as s Ga o, 65As layer 1
3: Each shows a p-type GaAs layer. Representative Patent Attorney Hei Tatsuyoshi

Claims (1)

[Claims] A multilayer structure having an active layer and a semiconductor layer sandwiching the active layer from above and below and having a larger forbidden band width than the active layer is provided on a semiconductor substrate, and the semiconductor layer is formed by penetrating the multilayer semiconductor layer including the active layer to the semiconductor substrate. The semiconductor is provided with a mesa region sandwiched between two band-shaped grooves that reach up to 100 cm, and the semiconductor is not stacked on the upper part of the mesa area including the active layer sandwiched by the band-shaped grooves, but is stacked on the side and other areas. At least one semiconductor layer having a forbidden band width larger than that of the substrate, and a semiconductor layer having a forbidden band width equal to or larger than the semiconductor substrate so as to cover the entire mesa region including the upper part thereof. A semiconductor laser characterized by: