JPH04237183A - Distorted quantum well laser - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser where a distorted quantum well large in tolerance to stress induced in a manufacturing process and laser oscilla tion is made to serve as an active layer by a method wherein the active layer is made to grow on a stepped substrate of inverted mesa structure, whereby it grows discontinuous. CONSTITUTION:A distorted quantum well laser is provided with an N-GaAs (100) stepped substrate 11 of inverted mesa structure and an InvGa1-vAs quantum well active layer 15 formed on the stepped substrate 11 through a molecular beam epitaxial growth method, where the active layer 15 is severed through the stepped part of the substrate 11 and in result enhanced in tolerance to stress which acts on it near a light emitting region.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a strained quantum well laser, which greatly contributes to improving the performance of compound semiconductor opto-electronic devices. Concerning a strained quantum well laser that is composed of two types of semiconductors with different band gaps, in which the other semiconductor is surrounded by the semiconductor with a large energy gap, and the quantum well that serves as the active layer has a different lattice constant from the substrate and is distorted. It is.

0002

[Prior Art] Conventionally, technologies in this field include:
For example, A. Lasson, S. Forouhar, J. Cod
y and R. J. Lang: "High-power operation of a highly reliable narrow stripe pushed morphic single quantum well laser oscillating at 980 nm" (High-Po
Were Operation of High
y Reliable Narrow Stri
pePseudomorphic Single
Quantum Well Lasers Emit
ting at 980 nm) IEEE P
HOTONICS TECHNOLOGY LET
TERS VOL. 2, No. 5, MAY, 1990
Year P. There was one described in 307-309.

FIG. 2 shows such conventional molecular beam epitaxial growth InGaAs/GaAs/AlGaAs GRI.
FIG. 3, which is a diagram showing the composition profile and layer thickness of N-SCH SQW, is a cross-sectional view of such a strained quantum well laser. As shown in these figures, the method for manufacturing this type of strained quantum well laser is to form an n-AlGaAs cladding layer 2 and an AlGaAs GRIN-SCH (Grate) on an n-GaAs substrate 1 by molecular beam epitaxial growth.
dIndexSeparate Confine
ment Heterostructure)+In
GaAs SQW (Single Quantum
Well) layer 3, p-AlGaAs cladding layer 4,
After laminating the p-GaAs contact layer 5, the p-GaAs contact layer 5 and the p-AlGa are deposited by dry etching or chemical etching to the vicinity of the active layer, leaving a stripe region of about 3 μm and forming a refractive index waveguide mechanism.
Most of the As cladding layer 4 was removed to form a ridge structure, and then an insulating film 6 was used to perform current confinement.

0004

[Problems to be Solved by the Invention] However, in the conventional strained quantum well laser manufacturing method described above, InGaAs, which is not lattice-matched to the substrate, is grown on the entire surface, and when the oscillation wavelength is lengthened, it is difficult to generate dislocations. Since it requires an active layer with a thickness close to the growth limit, it has the disadvantage that defects due to stress are likely to occur during the manufacturing process or during high-output oscillation, and the laser device deteriorates.

The present invention aims to eliminate the above-mentioned problem that stress applied to the entire surface of the active layer deteriorates the device, improve the characteristics, and provide a highly reliable strained quantum well laser. The purpose is

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a strained quantum well laser that includes a stepped substrate having an inverted mesa structure and a structure formed on the stepped substrate by molecular beam epitaxial growth. The active layer is separated from the active layer by the step of the substrate, thereby increasing the tolerance of stress applied to the active layer near the light emitting region.

[0007]

[Operation] As described above, the present invention uses a molecular beam epitaxial growth apparatus to form a semiconductor laser structure on a substrate with an inverted mesa step, and the step breaks the connection between the active layers and causes stress in the vicinity of the oscillation region. Tolerance can be increased. Therefore, unlike in the prior art, stress applied to the entire surface of the active layer does not cause deterioration of the device, and a highly reliable strained quantum well laser can be obtained.

[0008]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view showing the manufacturing process of a strained quantum well laser according to an embodiment of the present invention. First, as shown in FIG. 1(a), by molecular beam epitaxial growth, ordinary lithography technology and chemical etching, a stripe with a width of about 10 μm is formed in the <011> direction with an inverted mesa step.
- On a GaAs (100) substrate 11, an n-GaAs buffer layer 12 (about 0.5 μm), an n-AlX Ga1-
X As cladding layer 13 (approximately 1 μm), AlY Ga1
-Y As optical waveguide layer 14 (about 100 nm), InV G
a1-V As quantum well active layer 15, AlY Ga1-
YAs optical waveguide layer 16 (about 100 nm), p-AlX
Ga1-X As cladding layer 17 (approximately 1 μm), p-G
An aAs contact layer 18 (approximately 0.5 μm) is laminated.

The thickness and composition of the InV Ga1-V As quantum well active layer 15 are determined on the condition that the threshold current is minimized at the set oscillation wavelength. AlYGa1-Y
The composition of the As optical waveguide layers 14 and 16 is Y~0.
2, and Y in the AlX Ga1-X As cladding layer.
=X. Next, Figure 1(b
), a stripe with a width of about 3 μm is formed in the <011> direction at the center of the inverted mesa using normal lithography and dry etching techniques, and the area other than the stripe area is etched. Forms a ridge structure. This etching depth is AlYGa1-YAs
The optical waveguide layer 14 is not reached and a refractive index waveguide mechanism is built. An insulating film 19 is formed, and a p-GaAs contact layer 1 is formed using a normal lithography technique.
The insulating film on 8 is removed, and p-side electrode 20 is formed. Next, an n-side electrode 21 is formed on the back surface, and a laser end face is formed by dry etching or cleaving.

In the above embodiments, growth on an n-GaAs substrate was explained, but growth on a p-GaAs substrate may be used depending on the selection of impurities. Furthermore, the epitaxial growth regions other than those on the inverted mesa may also be removed by etching. Furthermore, InGaS on GaSb substrate
It can also be applied to the formation of b-quantum well lasers, GaInP quantum well lasers on GaP substrates, etc.

It should be noted that the present invention is not limited to the above embodiments, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

0012

Effects of the Invention According to the present invention, by growing an active layer on a substrate with steps having an inverted mesa structure, the connection between the active layers is severed by the steps, and the tolerance to stress generated during the manufacturing process and laser oscillation is improved. A highly reliable strained quantum well semiconductor laser can be obtained by manufacturing a semiconductor laser having a strained quantum well as an active layer with a large strained quantum well. The present invention can be applied to a wide range of fields such as ultra-high speed optical information processing and communication.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the manufacturing process of a strained quantum well laser according to an embodiment of the present invention.

[Figure 2] Conventional molecular beam epitaxial growth InGaAs
/GaAs/AlGaAs GRIN-SCH S
It is a figure which shows the composition profile and layer thickness of QW.

FIG. 3 is a cross-sectional view of a conventional strained quantum well laser.

[Explanation of symbols]

11 Inverted mesa stepped n-GaAs (100)
Substrate 12 n-GaAs buffer layer 13 n-AlX Ga1-X As cladding layer 14 AlY Ga1-Y As optical waveguide layer 15
InV Ga1-V As quantum well active layer 16
AlY Ga1-Y As optical waveguide layer 17
p-AlX Ga1-X As cladding layer 18
p-GaAs contact layer 19 insulating film 20 p-side electrode 21 n-side electrode

Claims (1)

[Claims] Claim 1: (a) A substrate with steps having an inverted mesa structure; (b)
) an active layer formed by molecular beam epitaxial growth on the stepped substrate; (c) the active layer is disconnected by the stepped substrate;
A strained quantum well laser characterized by increasing the tolerance of stress applied to the active layer near the light emitting region.