Method for manufacturing a semiconductor light emitting device

Details Method for manufacturing a semiconductor light emitting device Method for manufacturing a semiconductor light emitting device

1999-01-04

2001-03-13

Bowers, Charles (Department: 2813)

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Compound semiconductor

Reexamination Certificate

active

06200827

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a light emitting device.
Recently, the semiconductor light emitting device using gallium nitride and related compound semiconductors (hereinafter called III-V nitride semiconductors) has attracted a lot of attention. Accordingly, the device structure suitable for the III-V nitride semiconductor has been studied.
Here, III-V nitride semiconductor is defined as the semiconductor of the compound of GaN of III group atom with N of V group atom, the compound of Ga of III group atom with another III group atom such as Al, In and others which is substituted for a part of Ga, and the compound of N of V group atom with another V group atom such as P, As and others which is substituted for a part of N.
Heretofore, various types of element structure have been proposed in order to improve the characteristics of the semiconductor light emitting device. As a method for improving a basic characteristic such as the threshold of oscillation, there is a method for providing structure to restrict the path for electric current.
As one of the methods to restrict the electric current path, there is a method of removing an area around the path in a p-type layer of the surface of the semiconductor by wet etching or dry etching.
However, the method has following problems.
The method of wet etching can not be used, because an etching solution suitable for the semiconductor of the GaN related compound has not been discovered.
In the method by the dry etching, an active layer may be damaged by the etching of the p-type layer, thereby reducing the light emitting characteristic.
Therefore, at the present time, a method by annealing process is devised as shown in
FIGS. 3
a
and
3
b.
A semiconductor light emitting device of
FIG. 3
a
has a layer structure comprising a III-V nitride semiconductor on a substrate
21
, which comprises an n-type buffer layer
22
, n-type GaN clad layer
23
, n-type AlGaN clad layer
24
, InGaN active layer
25
, p-type clad layer
26
, and p-type GaN contact layer
27
.
In the method, the entire semiconductor layer is annealing-processed, thereby activating the p-type layers. Thereafter, a mask
28
of insulation material is mounted on the surface of the p-type contact layer
27
, and the semiconductor is annealing-processed in an ambient of hydrogen. As a result, p-type layers
29
not covered by the mask
28
are made high resistance to form a narrow electric current path as shown in
FIG. 3
a.
Next, the mask
28
is removed and a p-electrode
30
of Au is mounted on a current injection area of the p-type contact layer
27
as shown in
FIG. 3
b.
On the other hand, the n-type clad layer
23
is exposed by etching a part of the semiconductor layer (
FIG. 3
a
), and an n-electrode
31
of Au is mounted on the surface of the n-type clad layer
23
, thereby forming a semiconductor light emitting device (
FIG. 3
b
).
However, in the method, the mask
28
of insulation material must be removed, and the removed portion is exposed in the atmosphere. The exposed portion is oxidized to form an oxidation film on the portion. Furthermore, in order to reduce the contact resistance of the electrode
31
, the semiconductor layer is annealing-processed again. As a result, hydrogen diffuses from the high resistance portion to the low resistance portion of the narrow path, thereby increasing the resistance of the narrow path.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for making a semiconductor light emitting device which may easily form an electric current injection area, easily manufacture the light emitting device using mass production, and reduce the contact resistance with the electrode.
According to the present invention, there is provided a method for manufacturing a semiconductor light emitting device having a stack structure which consists of at least an n-type III-V nitride semiconductor layer, an active layer, and a p-type III-V nitride semiconductor layer on a substrate.
The method comprises the steps of a first annealing process for the purpose of activating the p-type III-V nitride semiconductor layer, forming a metal mask on the area of the III-V nitride semiconductor area where electric current is to be injected, a second annealing process for inactivating the p-type III-V nitride semiconductor layer except for the masked area.
The first annealing process is performed in an ambient of nitrogen, and the second annealing process is performed in an ambient including hydrogen or hydrides.
The method further comprises forming a p-electrode that covers the mask on the surface of the p-type and forming an n-electrode on the n-type III-V nitride semiconductor layer after the second annealing process.
The metal of the mask is one of Ni, Pt, Pd and Au.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.


REFERENCES:
patent: 08115880 (1996-05-01), None
S. Nakamura et al., “Thermal Annealing Effects on P-Type Mg-Doped GaN Films”, Jpn. J. Appl. Phys., vol. 31, pp. L139-L142, Feb. 1992.
W. Gotz et al., “Hydrogen passivation of Mg acceptors in GaN grown by metalorganic chemical vapor deposition”, Appl. Phys. Lett., vol. 67, pp. 2666-2668, Feb. 1992.

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