JPS61281561A - Manufacture of semiconductor-surface light-emitting element - Google Patents

Abstract

PURPOSE:To grow each layer constituting double hetero-junctions easily by growing an AlGaAs first clad layer, an AlGaAs active layer and an AlGaAs second clad layer forming the double hetero-junctions in a liquid-phase epitaxial manner in succession after a meltback process. CONSTITUTION:A P-type AlGaAs layer 11 is grown on an N-type GaAs spare substrate 10, and the back side of the spare substrate 10 is thinned up to thickness of approximately 10mum, and used as a current block layer 12. A circular hole 14 for a current path in depth reaching the AlGaAs substrate 11 is formed, and a circular groove 16 is further shaped through etching. A P-type AlGaAs first clad layer 20, a P-type AlGaAs active layer 22 and an N-type AlGaAs second clad layer 24 constituting double hetero-junctions are grown on the exposed surface through the formation of the hole 14 of the AlGaAs substrate 11 and the residual current block layer 12 in a LPE manner in succession. Accordingly, liquid-phase epitaxial growth can be conducted without difficulty onto the AlGaAs substrate, thus improving the crystallizability of each layer being grown.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Applications) This invention relates to a method of manufacturing a semiconductor surface emitting device for optical communication or information processing.

(Prior art) An example of this type of semiconductor surface emitting device is disclosed in Japanese Patent Application No. 59-176.
It is proposed in No. 3. The device structure proposed there is A
When applied to an IGaAs/GaAs type light emitting diode, the manufacturing method thereof is as follows.

First, a p-type GaAs substrate, and second, an n-type GaAs substrate for current confinement.
The aAS current blocking layer is grown by liquid phase epitaxial growth (hereinafter sometimes referred to as LPE growth) for the first time. Next, a circular hole for a current path is etched in the current blocking layer, and then a second LPE formation is performed to form a p-type AC
aAs cladding layer, p-type AJIGaAs active layer, n-type A
A JLG aAs cladding layer and an n-type GaAs cap layer are successively formed. Here, "continuously" means that wafers are not taken in and out of the growth furnace during the second LPE growth process.

(Problem that the invention seeks to solve).

When the device having the above structure is applied to a light emitting device with an emission peak of 870 nm or less, there is a problem that about 50% of the total power of light emitted from the active layer is absorbed by the GaAs substrate.

In order to reduce this absorption, AMG aA, which has a larger energy camp than the active layer, should be used instead of the GaAs substrate.
It is necessary to use an S substrate. However, AfLG
Since the surface of aAs is easily oxidized, if a hole for a current path is formed in the current blocking layer using ordinary wet I etching, the AuGaAs substrate will come into contact with the outside air and an oxidized layer will be formed on the surface.

Therefore, there was a problem in that the second liquid phase epitaxial growth on the AJLGaAs substrate 2 after the holes were formed was extremely difficult.

It is an object of the present invention to make it possible to make holes for current passage in a current blocking layer without forming an oxide layer on the surface of an AlGaAs substrate, and to continuously form holes in each layer constituting a double heterojunction after making the holes. An object of the present invention is to provide a method for manufacturing a semiconductor surface emitting device that can be grown without difficulty.

(Means for Solving the Problem) In order to achieve this object, according to the present invention, first, an AlGaAs layer of the first conductivity type is added to the GaAs preliminary substrate-1 of the second conductivity type serving as a current blocking layer. grow. In this case, the AlGaAs layer can be grown not only by liquid phase epitaxial growth but also by any other suitable method. Further, the energy gap of this AlGaAs layer is set to be larger than the energy gap corresponding to the emission wavelength of the active layer.

Next, the GaAs preliminary substrate is etched halfway through its thickness to form a circular groove, and then the wafer is placed in a growth furnace.
Using meltback during liquid phase epitaxial growth, G
A hole for a current path reaching the underlying AJI GaAs layer is formed in the aAs preliminary substrate. The spare substrate portion remaining after forming the hole for the current path acts as a current blocking layer.

The AuGaAs layer underlying the GaAs current blocking layer thus formed is used as the original substrate of this surface emitting device. In the following explanation, this AlGaAs layer will be referred to as Al
Sometimes referred to as a GaAs substrate.

Next, without taking the wafer out of the growth reactor, Al was applied to form a double heterojunction following the meltback process on the wafer in which the holes for current paths were formed.
A first GaAs cladding layer, an AJI GaAs active layer, and a second AJLGaAs cladding layer are then grown by liquid phase epitaxial growth.

Subsequently, after growing a layer such as a cap layer directly on the second cladding layer or by liquid phase epitaxial growth as required,
The n-side and p-side electrodes are respectively formed using a normal semiconductor technique such as vapor deposition or sputtering to complete a semiconductor surface emitting device.

(Function) As described above, according to the present invention, during the same liquid phase epitaxial growth process, meltback for forming a hole for a current path in a GaAs preliminary substrate and a double heterojunction following this meltback process are performed. Since each of the constituent layers is grown, the AlGaAs group that is to become the substrate is not exposed to the outside air during this liquid phase epitaxial growth process. Therefore, no oxide layer is formed on the surface of this AJI GaAs layer. Therefore, LPE growth of a double heterojunction layer can be performed without difficulty.

Furthermore, since the AJLGaAs substrate of the device does not absorb light, the light emitting output is about twice that of a conventional case using a GaAs layer as a substrate.

(Example) Examples of the semiconductor surface emitting device of the present invention will be described below with reference to the drawings.

This will be explained with reference to the manufacturing process diagrams shown in FIGS. 1(A) to 1(H). Each figure is a sectional view showing the state of the sea urchin /\ at the main manufacturing stage, and the /\ latching that represents the cross section is omitted except for a part. The dimensions, shapes, and arrangement relationships of each component are merely shown schematically to the extent that the present invention can be understood. Further, in the following embodiments, the first conductivity type is assumed to be a p-type, and the second conductivity type is assumed to be an n-type.

In this invention, first, an n-type GaAs preliminary substrate lO
' - p-type AlGaAs layer! 1 is grown in a first liquid phase epitaxial growth process to obtain a wafer as shown in FIG. 1(A). In this case, the thickness of the preliminary substrate IO is approximately 3504 m, and the layer thickness of the p-type AlGaAs layer 11 is approximately 300 pm. Further, this preliminary substrate IO is processed into a current blocking layer in a later process. Also, p-type AuG
The energy cap of the aAs layer 11 is set larger than the energy gap corresponding to the emission wavelength of the active layer for light emission, which will be described later.

Next, the back side of this GaAs preliminary substrate 1o is made to have a thickness of about 10 ILm by mechanical polishing and/or chemical etching with, for example, an ammonia-based etching solution, as shown in FIG.
The wafer is made into a state as shown in B). Hereinafter, this thinned GaAs preliminary substrate will be referred to as the current blocking layer 12, and the p-type A GaAs layer 11 will be referred to as the original substrate, that is, the current blocking layer 12.
This becomes a uGaAs substrate.

Next, in the vicinity of the current blocking layer 12 including the center of the surface emitting element, a circular current passage hole 14 with a depth of 9 reaching the AI Ga, A, s substrate 11 is formed (No.

lUi! J(D)). For this reason, as shown in FIG.
A circular groove 16 is etched to a depth of, for example, approximately 51 Lm (approximately 51 Lm deep). In this case, the etching solution is a sulfuric acid-based solution, for example, sulfur: hydrogen peroxide: water = 4:1.
:1 solution. Subsequently, this GaAs current blocking layer 12 is melted back.

For this reason, the grooved wafer is placed inside the liquid phase epitaxial, f&long ellipse for the second liquid phase epitaxial growth. As shown in FIG. 1 ([1), this LP
During E growth, the surface of the n-type GaAs current blocking layer 12 in which the grooves 16 are formed is brought into contact with a Ga solution 18 containing unsaturated GaAs as a solute to etch the current blocking layer 12, thereby forming a p-type AJI GaAS substrate. 11 surface is exposed. The LPE growth conditions for performing this meltback are, for example, a temperature of about 800° C. and a duration of about 5 minutes in an H 2 atmosphere.

Following this meltback, in the same LPE growth process in the same growth furnace, holes 14 are formed and exposed I11.
A first cladding layer 20 of p-type AJIGaAs constituting a double heterojunction (DH) on the surface of the AJIGaAs substrate 11 and the remaining current blocking layer 12-F;
A p-type AlGaAs active layer 22 and an n-type AuGaAs second cladding layer 24 are sequentially grown by LPE (see FIG.
G)).

In this case, the first cladding layer 20 of p-type AJIGaAs is grown to a thickness of about 2 pm by bringing the surface of the underlying p-type AJIGaAs substrate 11 into contact with a supersaturated Ga solution, as shown in FIG. 1(E). obtain a suitable wafer condition. L at this time
The PE growth conditions are an H2 atmosphere, a temperature of about 795° C., and a duration of about 2 minutes.

, Incidentally, the first cladding layer 2 of this pffiAlGaAs
0 acts to confine carriers injected into the pn junction in the active layer 22.

Subsequently, the surface of the first cladding layer 20 of p-type AIGaAS is brought into contact with a supersaturated Ga solution to form the active layer 2 of p-type A n Ga A,s for light emission.
2 to a thickness of about 17 zm to obtain a wafer state as shown in FIG. 1(F). The PE growth conditions at this time are:
In an H2 atmosphere, the temperature is set to about 794° C. for about 1 minute.

Next, following this, the surface of this p-type AJI GaAS active layer 22 is brought into contact with a supersaturated Ga solution to form an n-type AJI GaAS active layer 22.
A second cladding layer 24 of JIGaAs is grown to a thickness of about 51 Lm to obtain a wafer state as shown in FIG. 1(G). The LPE growth conditions at this time are an H2 atmosphere, a temperature of about 793° C., and a duration of about 5 minutes. The second cladding layer 24 of n-type AuGaAs functions to confine carriers injected into the pn junction in the active layer 22.

Thereafter, an electrode metal layer, such as a Cr-A, U layer, is deposited on the p-type A1GaAs substrate 11. Thereafter, the p-side electrode 2B and the light extraction window 3o are formed in the Cr--Au layer by selective etching or a lift-off process. Furthermore, n
An electrode metal layer such as an Au-Ge-Ni alloy layer is deposited on the second cladding layer 24-1- of type AJI GaAs to form the n-side electrode 28, and a semiconductor surface emitting device as shown in FIG. complete.

This invention is not limited to the embodiments described above. For example, the layer structure of the light emitting device of the present invention is not limited to the above layer structure as long as it has an internal current blocking layer.

Moreover, the numerical examples explained in the embodiments described above are not limited to these, and may be changed to arbitrary suitable values according to the design.

Further, the first conductivity type is an n conductivity type, and the second conductivity type is a p conductivity type.
conductivity type, and necessary changes can be made accordingly.

(Effects of the Invention) As is clear from the above description, according to the method for manufacturing a semiconductor surface emitting device of the present invention, G
Since the melt-back process for forming holes for current paths in the aAs current blocking layer and the liquid phase epitaxial growth of each layer constituting the double heterojunction are performed in succession, G
The surface of the A-type GaAs substrate underlying the aAs current blocking layer is not oxidized. Therefore, two consecutive liquid phase epitaxial growths can be carried out on this AuGaAs substrate 1- without difficulty, and each layer grown has excellent crystallinity.

Further, according to the present invention, the manufacturing process is simplified because the G a As f @ substrate is used as the current blocking layer.

In addition, since the AJljGaAs substrate of the fabricated device does not absorb light, the light reflected by the n-side electrode can also be extracted as output, and the light emitting output is therefore increased to about twice that of the conventional device. Therefore, this element can be applied not only to optical communications but also to the field of optical information processing.

Incidentally, the surface emitting device manufactured by the method of the present invention produces a lens effect due to the curvature of the active layer, so that the light output has directionality and the coupling efficiency with the optical fiber is increased.

[Brief explanation of drawings]

FIGS. 1A to 1H are manufacturing process diagrams for explaining the manufacturing method of the semiconductor surface emitting device of the present invention. lO...GaAs preliminary substrate 11...-AuGaAs layer (or AlGaAs substrate) 1
2...GaAs current blocking layer I4...hole for current passage, ! 8...Circular groove 18
...Ga solution, 20...first cladding layer 2
DESCRIPTION OF SYMBOLS 2...Active layer, 24...Second layer, second layer 2B...p-side electrode, 28...n-side electrode 30...light extraction window. Patent applicant Oki Electric Industry Co., Ltd.

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Claims (1)

[Claims] (1) Second conductivity type GaA used as current blocking layer
a step of growing an AlGaAs layer of the first conductivity type on the preliminary substrate; a meltback step of liquid phase epitaxial growth for forming a hole for a current path in the preliminary substrate; and subsequent to the meltback step, A method for manufacturing a semiconductor surface emitting device, comprising the step of sequentially growing a first cladding layer, an active layer, and a second cladding layer forming a double heterojunction by liquid phase epitaxial growth on a current blocking layer with holes.