Epitaxial growth of nitride semiconductor device

Details Epitaxial growth of nitride semiconductor device Epitaxial growth of nitride semiconductor device

2002-11-13

2004-08-10

Jackson, Jerome (Department: 2815)

Active solid-state devices (e.g., transistors, solid-state diode

Heterojunction device

With lattice constant mismatch

C257S013000, C257S097000, C257S103000, C372S043010

Reexamination Certificate

active

06774410

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a light emitting semiconductor device with reducing dislocation density of epitaxial growth.
2. Description of the Related Art
AlInGaN-based compound semiconductor materials are frequently applied to produce light emitting devices such as blue-green light emitting diodes and laser diodes. Theses materials are usually grown on aluminum oxide (Al
2
O
3
) or silicon carbide (SiC) substrates.
The semiconductor materials are difficult to directly grow on the substrates because of lattice constant differences. For example, a GaN crystal layer (a=3.189 Å) is hard to directly grow on an aluminum oxide substrate (a=4.758 Å) since the difference of their lattice constants exceeds 16%.
Akasaki et al., in U.S. Pat. No. 4,855,249, first disclosed to grow at a low temperature an amorphous AlN buffer layer on an Al
2
O
3
substrate so as to reduce problems of the lattice constant differences between the Al
2
O
3
substrate and a GaN layer. Nakamuraet al., in U.S. Pat. No. 5,290,393, disclosed to use GaN or AlGaN as a buffer layer. An amorphous GaN buffer layer was first grown at a temperature between 400 and 900° C. on an Al
2
O
3
substrate. A GaN epitaxy layer was then grown at a temperature between 1000 and 1200° C. on the GaN buffer layer. The quality and performance of the GaN epitaxy layer were better than those of a GaN epitaxy layer produced by using AlN as a buffer layer.
Conventionally, nucleuses with one single species are grown between a substrate and a buffer layer so as to balance the lattice constant differences. However, the single-species nucleuses on the substrate still exhibit more occurrence chances of dislocation defects. Please refer to
FIGS. 1
a
to
1
d
in describing how the dislocation defects tend to occur according to prior art. In
FIG. 1
a
, nucleuses
101
are grown on a substrate
1
. Next, a buffer layer
103
is gradually grown on the substrate
1
and the nucleuses
101
as shown in
FIG. 1
b
. After completion of the buffer layer
103
, which is shown in
FIG. 1
c
, dislocation defects
104
mostly occur along sides of two nucleuses
101
. In
FIG. 1
d
, after growing an epitaxy layer
105
, the dislocation defects
104
further extend within the epitaxy layer
105
. The dislocation defects
104
reduce both electronic and optical performance of a light emitting device.
There always exists a need to reduce the lattice constant differences between an epitaxy layer and a substrate, ex. between a GaN-based epitaxy layer and an aluminum oxide substrate, since the differences result in dislocation defects of the epitaxy layer and even reduce performance of a semiconductor device thus produced.
SUMMARY OF THE INVENTION
The present invention provides a semiconductor device which comprises a monocrystalline substrate, multiple nucleuses on the monocrystalline substrate, a dislocation inhibition layer on the multiple nucleuses, and an epitaxy layer on the dislocation inhibition layer. The multiple nucleuses are made of at least two materials having different crystal constants. The multiple nucleuses are respectively isolated. Preferably, the multiple nucleuses are 10 Å to 100 Å thick.


REFERENCES:
patent: 5909040 (1999-06-01), Ohba et al.
patent: 6051847 (2000-04-01), Oku et al.
patent: 6555846 (2003-04-01), Watanabe et al.
patent: 6580098 (2003-06-01), Koide
patent: 6664560 (2003-12-01), Emerson et al.

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