JPH04237182A - Manufacture of distorted quantum well laser - Google Patents

Abstract

PURPOSE:To enable a distorted quantum well laser to be sharply shortened in manufacturing time and lessened in oscillation threshold current, temperature dependence, and emission beam width by a method wherein the distorted quan tum well laser structure provided with a current constriction mechanism and a refractive index waveguide mechanism is formed through the growth of crys tal. CONSTITUTION:An N-AlGaAs clad layer 12 and a GaAs light guide layer are formed on an N-GaAs substrate 11 through a molecular beam epitaxial growth method, and a process through which a stripe-like mask 14 is set above the substrate and another process through which the diffusion of atoms is controlled in the growth of a distorted quantum well which serves as an active layer to form a GaAs buried layer 16 where an InGaAs quantum well active layer 15 is buried are provided.

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. In other words, it is 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 serving as the active layer has a different lattice constant from the substrate and is distorted. The present invention relates to a manufacturing method.

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. 3 shows such conventional molecular beam epitaxial growth InGaAs/GaAs/AlGaAs GRI.
FIG. 4, 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 above-mentioned method for manufacturing a strained quantum well laser, it is difficult to precisely produce the ridge structure for fundamental transverse mode oscillation by chemical etching, and by dry etching, There was a drawback that the active layer was damaged. In addition, since InGaAs, which is not lattice matched to the substrate, is grown on the entire surface,
There is a drawback that defects occur due to stress during high-output oscillation, and the laser element deteriorates.

The present invention eliminates the above-mentioned problems when fabricating a ridge structure by etching and stress applied to the entire surface of the substrate, and creates a strained quantum well laser with improved characteristics and high reliability. The purpose is to provide a manufacturing method.

[0006]

[Means for Solving the Problems] According to the present invention, in order to achieve the above object, a step of forming a substrate portion on which a cladding layer and an optical waveguide layer are formed by molecular beam epitaxial growth on a substrate; A step in which a striped mask is set above the active layer and a molecular beam epitaxial growth method is used to control the diffusion of atoms during growth of the strained quantum well that will become the active layer, forming a buried layer that buries the strained quantum well active layer. The process is as follows.

[0007] Furthermore, the step of embedding the strained quantum well active layer involves growing the strained quantum well active layer in a minute region,
This is done by feeding Group II and V raw materials alternately and simultaneously. Furthermore, the strained quantum well active layer is made of InGaA
The buried layer is made of GaAs.

[0008]

[Operation] According to the present invention, as described above, a strained quantum well active layer is grown in a minute region by molecular beam epitaxial growth using a striped mask, and
, V group raw materials are supplied alternately and simultaneously to embed the active layer. Therefore, since a strained quantum well laser structure having a current confinement mechanism and a refractive index waveguide mechanism can be formed by crystal growth, the time for manufacturing a laser device can be significantly shortened.

Furthermore, by manufacturing a semiconductor laser in which the active layer is a strained quantum well formed only in the fabrication stripe region, it is possible to reduce the oscillation threshold current, temperature dependence, and emission line width. , it is possible to obtain an increased modulation frequency and a highly reliable laser.

0010

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 Figure 1(a), n-GaA
On the s(001) substrate 11, an n-AlGaAs cladding layer 12 (approximately 1 μm) and a GaAs optical waveguide layer 13 (approximately 20 nm) are formed.
m) is laminated. In other words, a substrate portion is formed.

Next, as shown in FIG. 1(b), the width is 3 μm.
Cover with a striped mask 14 of about 100 mL. Therefore,
As shown in Figure 2, the shutter is closed for a few seconds, all raw material supply is stopped, and the Ga shutter is opened (t1). After irradiating a Ga beam of approximately one atomic layer, the shutter is closed and the Ga beam is
Facilitates surface diffusion of atoms. Next, the As shutter is opened (t2), followed by the In shutter (t3), and after irradiating the In beam of one atomic layer or less, the I
Close the n shutter, then close the As shutter, and then
Suppresses surface diffusion of atoms. After a few seconds, the Ga shutter is opened (t4) and irradiation with about one atomic layer of Ga is repeated until the InGaAs quantum well active layer 15 and the GaA
An s-buried layer 16 is simultaneously formed in the stripe region. The amount of In beam supplied is set to be one atomic layer or less so that the oscillation wavelength and threshold current are minimized. The thickness of the InGaAs quantum well active layer 15 is also determined by this condition. Furthermore, G
The aAs optical waveguide layer 17 (about 20 nm) is also formed by a growth method in which Ga and As beams are alternately supplied in layers of about one atomic layer.

[0012] Next, p-AlGaA is grown using a normal growth method.
An s-cladding layer 18 (approximately 1 μm) and a p-GaAs contact layer 19 (approximately 0.5 μm) are formed in the stripe region. On the mask 14, InGaAs polycrystal 23, GaA
S polycrystal 24, AlGaAs polycrystal 25, and GaAs polycrystal 26 are stacked. Next, as shown in FIG. 1C, an insulating film 20 is formed, and the insulating film on the p-GaAs contact layer 19 is removed using a normal lithography technique to form a p-side electrode 21. Next, the n-side electrode 2 is placed on the back side.
2 is formed, and a laser end face is formed by dry etching or cleavage.

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, GaS
It can also be applied to the formation of an InGaSb quantum well laser on a b substrate, a GaInP quantum well laser on a GaP substrate, etc. Note that the present invention is not limited to the above-mentioned 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.

[0014]

[Effects of the Invention] As explained in detail above, according to the present invention, a strained quantum well laser structure having a current confinement mechanism and a refractive index waveguide mechanism can be formed by crystal growth, so that the manufacturing time of a laser device can be significantly reduced. Can be shortened. In addition, by manufacturing a semiconductor laser in which the active layer is a strained quantum well formed only in the fabricated stripe region, it is possible to reduce the oscillation threshold current, reduce temperature dependence, and reduce the emission line width.
It is possible to increase the modulation frequency and obtain a highly reliable laser. 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] Ga, In, A during fabrication of strained quantum wells of the present invention
5 is a flowchart for opening and closing the s-shutter.

[Figure 3] 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. 4 is a cross-sectional view of a conventional strained quantum well laser.

[Explanation of symbols]

11 n-GaAs (001) substrate 12
n-AlGaAs cladding layer 13 GaAs optical waveguide layer 14 mask 15 InGaAs quantum well active layer 16
GaAs buried layer 17 GaAs optical waveguide layer 18 p-AlGaAs cladding layer 19
p-GaAs contact layer 20 insulating film 21 p-side electrode 22 n-side electrode 23 InGaAs polycrystal 24 GaAs polycrystal 25 AlGaAs polycrystal 26 GaAs polycrystal

Claims (3)

[Claims] 1. (a) forming a substrate portion on which a cladding layer and an optical waveguide layer are formed by molecular beam epitaxial growth, and (b) setting a striped mask above the substrate portion. (c) controlling the diffusion of atoms during growth of the strained quantum well that will become the active layer using a molecular beam epitaxial growth method to form a buried layer that buries the strained quantum well active layer. A method for manufacturing strained quantum well lasers. 2. In the step of embedding the strained quantum well active layer, the strained quantum well active layer is grown in a micro region, and
2. The method of manufacturing a strained quantum well laser according to claim 1, wherein the I and V group raw materials are supplied alternately and simultaneously. 3. The strained quantum well active layer is made of InGaA.
2. The method of manufacturing a strained quantum well laser according to claim 1, wherein the buried layer is made of GaAs.