JPH0818155A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To prevent strain from being relaxed on the edge intersecting the laser discharging direction perpendicularly by forming a semiconductor, while matching the lattice with a substrate, on the edge intersecting the laser discharging direction perpendicularly. CONSTITUTION:A resist film 9 3mum wide is formed in a region corresponding to a stripe formed perpendicularly to a cleavage plane. The upper part of a cap layer 8 and an upper clad layer 7 is then removed by etching from the region formed with no resist film 9 using the resist trim 9 as a mask and an insulating film 10 of SiO2 is formed in that region. The used resist film 9 is then removed. An InGaP layer formed on the edge of a resonator has a lattice matching with those of a substrate 1 of GaAs, a buffer layer 2 of GaAs, the upper and lower clad layers 3, 7 of AlGaAs, and carrier confinement layers 4, 6 of GaAs, the semiconductor laser is provided with a function for preventing the compression strain in a strained quantum well layer 5 from being relaxed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in semiconductor laser devices. In particular, it relates to an improvement in improving the emission efficiency and reliability of a semiconductor laser device having a strained quantum well layer as an active layer.

[0002]

2. Description of the Related Art In a quantum well in which a band gap of a semiconductor forming an active layer is made smaller than a band gap of a layer surrounding the active layer and carriers are confined in the active layer to activate recombination, The lattice constant of the semiconductor forming the active layer is slightly different from that of the layer surrounding the active layer, and the
In a strained quantum well in which strain is applied, degeneration of the valence band is released, the band gap is increased, the effective mass of carriers is reduced, and the density of states of the valence band is reduced. Are known. Therefore, in the semiconductor laser device having such a strained quantum well layer as an active layer, the threshold current is reduced and the absorption between valence bands is reduced, so that the light emission efficiency is improved.

[0003]

However, in the semiconductor laser device using the strained quantum well layer as the active layer, the strain is released at the end face orthogonal to the laser emission direction, the absorption increases, and the desired luminous efficiency is obtained. Cannot be obtained, or the deterioration of the end face is promoted, and the reliability tends to decrease.

An object of the present invention is to eliminate these drawbacks, and in a semiconductor laser device having a strained quantum well layer as an active layer, strain is not released at the end face orthogonal to the laser emission direction, and luminous efficiency is improved. To provide a highly reliable semiconductor laser device.

[0005]

The above object is to provide a semiconductor laser device having a strained quantum well layer as an active layer, in which a semiconductor layer is formed on an end face orthogonal to a laser emission direction in lattice matching with a substrate. Is achieved by a semiconductor laser device.

[0006]

In the semiconductor laser device having the strained quantum well layer as the active layer according to the present invention, the semiconductor layer is formed on the end face orthogonal to the laser emission direction in lattice matching with the substrate. The strain is not released even on the end face orthogonal to the above, and therefore the absorption is not increased, the threshold current is low, and the light emission efficiency is high.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A manufacturing process of a semiconductor laser device according to an embodiment of the present invention and effects peculiar to the present invention will be described below with reference to the drawings.

See FIG. 2. An n-type G is formed by using a low pressure metal organic vapor phase epitaxy method (hereinafter referred to as a low pressure MOCVD method) performed at a growth temperature of 700 ° C.
A buffer layer 2 made of an n-type GaAs layer having a thickness of 500 nm and an n-type AlGaAs having a thickness of 2 μm are formed on an aAs substrate 1.
Lower clad layer 3 consisting of layers and GaA having a thickness of 50 nm
Carrier confinement layer 4 consisting of s layer and I with a thickness of 9 nm
Strained quantum well layer 5 made of nGaAs layer and having a thickness of 50 nm
Carrier confinement layer 6 made of a GaAs layer and having a thickness of 2
Upper clad layer 7 made of p-type AlGaAs layer of μm
And a cap layer 8 made of a p-type GaAs layer having a thickness of 500 nm are successively formed. A compressive strain of 1.5% is applied to the strained quantum well layer 5 manufactured by this process.

Referring to FIG. 3, a resist film 9 having a width of 3 μm is formed in a region corresponding to a stripe formed orthogonal to the cleavage plane, and the resist film 9 is formed.
Using as a mask, the cap layer 8 and the upper portion of the upper cladding layer 7 are removed by etching from the region where the resist film 9 is not formed. Then, the insulating film 10 made of SiO ₂ is formed in the removed region. The used resist film 9 is removed.

FIG. 4 shows a cross section taken along the line AA shown in FIG.

A resonator is formed by cleavage at 1 mm intervals in a direction orthogonal to the stripe.

An InGaP layer 11 having a thickness of 150 nm is formed on the end face of the resonator by using a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method) performed at a growth temperature of 600 ° C. The InGaP layer 11 includes the substrate 1 made of GaAs and the buffer layer 2 made of GaAs.
The upper and lower cladding layers 3 and 7 made of As and the carrier confinement layers 4 and 6 made of GaAs are lattice-matched with each other, so that the strain quantum well layer 5 has a strain release preventing function for preventing release of compressive strain. .

Referring to FIG. 1, a positive electrode 12 made of a Ti / Pt / Au layer is formed on the upper surface and the side surface of the cap layer 8 and on the side surface and the upper surface of the upper cladding layer 7.

After polishing the substrate 1 to a thickness of about 100 μm, the negative electrode 1 made of AuGeNi / Au layer is formed on the lower surface of the substrate 1.
3 is formed.

On the laser emitting end face, SiN having a reflectance of 5% is used.
A laminated body 15 of amorphous silicon having a reflectance of 95% and SiO ₂ is formed on the film 14 on the laser reflecting surface.

The semiconductor laser device manufactured through the above steps was oscillated at 60 ° C. by supplying electric power of 200 mW. 2 by the time the drive current increases by 50%
Since it took 0,000 hours, the life was satisfactory. As a comparative example, a semiconductor laser device having no InGaP layer 12 was subjected to a life test under the same conditions, and it was 120,000 hours.

In the above embodiment, the InGaP layer is used as the layer having the strain release preventing function.
When the substrate is a GaAs substrate, in addition to the InGaP layer,
AlGaAs layer, AlGaInP layer, GaAs layer, etc.
It can be used as a layer having a strain release preventing function.

In addition, the InGaP layer, I
It can be used also in the case of a visible light laser in which the nGaAlP layer is formed as a compressive strain quantum well layer, but it is necessary to use at least a semiconductor transparent to the oscillation wavelength as a layer having a strain release preventing function. So in this case
The Al composition is higher than that of the semiconductor of the strained quantum well layer, and
InGaAlP having a mixed crystal ratio that lattice-matches GaAs
Need to use.

[0019]

As described above, in the semiconductor laser device according to the present invention, in the semiconductor laser device having the strained quantum well layer as the active layer, the end face orthogonal to the laser emission direction is
Since the semiconductor layer is formed by lattice matching with the substrate,
The strain is not released at the end surface orthogonal to the laser emission direction, the threshold current is low, the light emission efficiency is high, and the life is long.

[Brief description of drawings]

FIG. 1 is a layer configuration diagram of a semiconductor laser device according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of a semiconductor laser device according to an embodiment of the present invention (epitaxial layer formation).

FIG. 3 is a manufacturing process diagram of a semiconductor laser device according to one embodiment of the present invention (stripe and insulating layer formation).

FIG. 4 is a manufacturing process diagram of a semiconductor laser device according to an embodiment of the present invention (formation of a layer having a strain release preventing function).

[Explanation of symbols]

1 n-type GaAs substrate 2 buffer layer made of n-type GaAs 3 lower clad layer made of n-type AlGaAs 4 carrier confinement layer made of GaAs 5 strained quantum well layer made of InGaAs 6 carrier confinement layer made of GaAs 7 made of p-type AlGaAs Upper clad layer 8 Cap layer made of p-type GaAs 9 Resist film 10 Insulating film made of SiO ₂ 11 Layer having a strain relief preventing function made of InGaP 12 Positive electrode made of Ti / Pt / Au 13 Negative electrode made of AuGeNi / Au 14 SiN film 15 Laminated body of amorphous silicon and SiO ₂

Claims (1)

[Claims] 1. A semiconductor laser device having a strained quantum well layer as an active layer, wherein a semiconductor layer is formed on an end face orthogonal to a laser emission direction in lattice matching with a substrate. .