JPS62196874A - Semiconductor light emitting element and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the yield of a product by absorbing the oozed impurity from a substrate by a buffer layer to effectively obtain the desired thickness of a current barrier layer. CONSTITUTION:An impurity Ge-doped P-type GaAs buffer layer 6 is formed on an impurity Zn-dped P-type GaAS substrate 1. Then, Te is doped in the layer 6 to form an n-type GaAs current barrier layer 2. Then, the impurity Zn is selectively diffused in the layer 2 to form a P-type current constriction region 3. Then, a GaAlAs double hetero junction layer 4 is formed on the region 3 and the layer 2. Then, a first ohmic electrode 5a is formed on the bottom of the substrate 1, and a second ohmic electrode 5b is formed on the upper surface of the layer 4.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a high-output semiconductor light emitting device used in, for example, a light emitting device for 0.8 μm band optical communication and a light source for autofocus of a camera, and its construction. It is about the method.

[Conventional technology]

There is a semiconductor light emitting device shown in FIG. 2 that requires narrow directivity and is used as a high output light source.

It is formed near its center by selective diffusion: a
'! ! ! An n-type current barrier layer 2 having a region (p-type current confinement region) 3 is formed on a p-type GaAs substrate l.

Moreover, a GaAjAs double heterojunction layer 4 is formed on the electrical barrier layer 2 and the current-carrying region 3.

Note that this double heterojunction layer 4 has p-type Aj in order from the bottom.
It has three layers: a GaAs cladding 4a, a p-type AA) aAs layer 4b, and an n-type AJGaAs cladding layer 4C.

A p-side ohmic electrode 5a is formed on the bottom surface of the substrate 1, and an n-type ohmic electrode 5a is formed on the periphery of the top surface of the n-type A phantom aAs/il 4c.
A side ohmic current 5b is formed.

According to the light emitting device as described above, by applying a positive voltage to the p-side electrode 5a and a negative voltage to the n-side electrode 5b, the current focused by the aforementioned current-carrying region 3 is transferred to the double heterojunction layer 4i. high output light with narrow directivity is obtained.

[Problem that the invention seeks to solve]

In the manufacturing process of the conventional light emitting device as described above, impurity Zn is added to the p-type GaAs substrate 1 at a depth of approximately 10"cm-3-
It is doped with a carrier concentration of about

Then, to the n-type current barrier layer 2 on this substrate 1.

When the conductive region 3 is formed by selective diffusion, the above-mentioned impurity Zn in the substrate 1 seeps into the n-type barrier layer 2. For this reason, the n-type barrier layer 2 becomes p-type and disappears, resulting in the production of devices (defective products) in which the current confinement effect cannot be obtained.

Furthermore, even if this n-type barrier layer 2 does not completely disappear,
A device is produced in which this barrier layer 2 is thinner than the desired thickness. The characteristics of such an element deteriorate rapidly during operation.

This is considered to be due to the fact that the barrier layer 2 is thin and a leakage current occurs in a certain portion of the barrier layer 2.

For example, when the current was applied for 5 hours under the conditions of 300 mA and 1/2 duty, the number of elements with this characteristic deterioration was 3.
oa/.

It also reached

One possible solution to this problem is to form the barrier layer 2 thick in advance, but in this case, the conditions for selective Zn diffusion must also be strengthened when forming the p-type current confinement layer 3. Therefore, the seepage of Zn from the substrate 1 also increases, and this is not a fundamental solution.

[Means to solve the problem]

In the present invention, in order to solve the above conventional problems,
A p-type buffer layer is provided between the substrate and the barrier layer so that the impurity Zn seeping out from the p-type substrate cannot reach the current barrier layer, and the impurities in the parenthetical buffer layer have a higher diffusion coefficient than the impurities in the p-type substrate. This also controls impurity seepage from this buffer layer.

[Effect]

According to the present invention, in order to form a buffer layer doped with an impurity having a lower diffusion coefficient than the impurity of the substrate between the substrate and the current barrier layer, this buffer layer absorbs impurity seepage from the substrate. .

Therefore, adverse effects on the current barrier layer due to seepage of impurities can be avoided.

〔Example〕

An embodiment of the present invention will be described with reference to FIG.

First, the manufacturing process will be explained.

(1) LPE method (liquid phase epitaxial method) on p-type GaAs substrate 1 doped with impurity Zn (first impurity)
As a result, a p-type GaAs buffer layer 6 doped with impurity Ge (second impurity) is formed to a thickness of about 10 μm. The carrier concentration (doping amount) of this Ge is
When this element is in operation (when energized).

The higher the concentration, the better in order to reduce the voltage drop, but if the concentration is too high, crystallinity will deteriorate. Therefore, in this embodiment, the angle was set to about 2xlO"cm-'i degrees.

(2) Next, continuously apply T to the buffer layer 6 by LPE method.
A doped n-type GaAs current barrier layer 2 is formed to a thickness of 5 μm.

(3) Next, a p-type conductive region (current confinement region) 3 is formed by selectively diffusing impurity Zn into this current barrier layer 2. This selective diffusion.

A SiN film (not shown) is formed on the current barrier layer 2, and an opening of 60 to 120 μΦ is formed near the center of the SiN film by photolithography.
This is done by diffusing n.

(4) After removing the SiN film pattern, GaAl is deposited on the current barrier layer 2 and current confinement region 3 by LPB method.
As double heterojunction layer 4. In other words, from the bottom, the p-type
o, pt, A'o, st As clad 4a, p-type Ga
o,@.

A.J. , As active layer 4b, n-type Ga0. ．．
Three layers of AL (1,3As cladding layer 4C) are formed.

(5) Next, AuBe is deposited on the bottom surface of the p-type GaAs substrate 1.
(gold beryllium) alloy electrode (first open electrode)
An AuGe (gold germanium) alloy electrode (second Au Z electrode) is formed on the upper surface of the n-type cladding layer 4C. Then, in the portion of the AuGe electrode on the n-type cladding layer 4C located above the aforementioned current confinement region 3, an opening for light extraction is formed with a size of about 150 μmφ.

The light emitting element formed by the above steps is diced into approximately 600 μm square pieces, and a transparent glass ball lens with a size of approximately 300 μΦ is placed in the opening of the AuGe electrode, and is fixed onto this element with a transparent resin.

A light emitting device manufactured by such a process.

The seepage of impurity Zn from the substrate 1 does not reach the current #wall layer 2, and the seepage from the buffer NJ6 is extremely small, so that the desired current barrier layer 2 can be reliably formed. In fact, the product yield (yield of non-defective products) was approximately 100''A.

In actual use of this device, by applying a positive voltage to the first ohmic electrode 5a and a negative voltage to the second ohmic electrode I, the current focused by the constriction region 3 is transferred to the double heterojunction layer. 4, high-output light emission can be obtained, but the device reliability test (applied current 30
When electricity was applied for 5 hours under the conditions of 0 mA and 1/2 duty, there were almost no elements whose optical output deteriorated.

Therefore, a highly reliable element can be reliably obtained.

In addition, there is almost no deterioration in device performance due to the formation of the buffer layer 6, and high output light emission with narrow directivity can be obtained.

〔Effect of the invention〕

According to the present invention, by absorbing impurity seepage from the substrate by the buffer layer, it is possible to reliably obtain a current barrier layer with a desired thickness, thereby significantly improving product yield. Furthermore, the reliability of the element itself is improved, and characteristic deterioration hardly occurs.

There is an effect.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a light emitting device according to an embodiment of the present invention. FIG. 2 is a sectional view of a conventional light emitting device. 1... P-type GaAs-based substrate 2... N-type current barrier layer 3... P-type current confinement region 4... AJaAs double heterojunction layer 5a, 5b...
・Ohmic electrode 6...buffer layer Figure 1 Figure 2

Claims (5)

[Claims] (1) First conductivity type GaAs doped with first impurity
forming a first conductivity type buffer layer doped with a second impurity having a smaller diffusion coefficient than the first impurity on the system substrate; and forming a second conductivity type current barrier layer on the buffer layer. forming a current confinement region of the first conductivity type in the current barrier layer by selective diffusion; forming a GaAlAs double heterojunction layer on the current confinement region and the current barrier layer; A method for manufacturing a semiconductor light emitting device, comprising the steps of forming a first ohmic electrode on the bottom surface of the substrate and forming a second ohmic electrode on the top surface of the double heterojunction layer. (2) Claim 1, characterized in that the first impurity is Zn and the second impurity is Ge.
) The method for manufacturing a semiconductor light emitting device according to item 1. (3) The method for manufacturing a semiconductor light emitting device according to claim (1), wherein the buffer layer is formed to have a thickness of approximately 10 μm, and the current barrier layer is formed to have a thickness of approximately 5 μm. (4) The second impurity is approximately 2×10^1^8cm^-
3. The method of manufacturing a semiconductor light emitting device according to claim 1, wherein the buffer layer is doped with a concentration of ^3. (5) a GaAs-based substrate having a first conductivity type; a buffer layer of the first conductivity type formed on one principal surface of the substrate;
A current barrier layer having a second conductivity type formed on this buffer layer, a current confinement region formed in this barrier layer, and a GaAlAs double hetero layer formed on this current confinement region and the current barrier layer. A semiconductor light emitting device comprising a bonding layer, a first electrode formed on the other main surface of the substrate, and a second electrode formed on the double heterojunction layer.