Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With housing or contact structure
Reexamination Certificate
1998-03-24
2001-03-13
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With housing or contact structure
C257S773000
Reexamination Certificate
active
06201265
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a group III-V type nitride compound semiconductor device and a method of manufacturing the same, and in particular to a group III-V type nitride compound semiconductor device which has a characteristic in its electrode structure and a method of manufacturing the same.
2. Description of the Background Art
Group III-V type nitride compound semiconductor devices have been conventionally fabricated by using sapphire and spinel as the substrate material. It is also necessary to form a cavity by cleaving in fabricating semiconductor devices, particularly semiconductor lasers. This requires use of a substrate material which has cleavage. However, neither sapphire nor spinel have cleavage. Accordingly, semiconductor lasers are fabricated by using an oxide material, such as LiAlO
2
, LiGaO
2
, as substrate material.
Such a substrate material as sapphire, spinel, LiAlO
2
, LiGaO
2
and the like are, however, insulators. Accordingly, in forming an electrode in a proximity of a substrate (i.e., a lower electrode), various techniques are required as described below.
As one example of technique for forming an electrode in a proximity of a substrate, Japanese Patent Laying-Open No. 8-17803 discloses that a grown film of a group III-V type nitride compound semiconductor is partially removed by dry etching or the like to form an electrode in a proximity of a substrate.
FIG. 34
is a perspective view of a light-emitting diode device as one example of a conventional group III-V type nitride compound semiconductor device, with application of the technique of etching a grown film to form an electrode in a proximity of a substrate.
Referring to
FIG. 34
, the light-emitting diode device has an n-type contact layer
3
, an n-type clad layer
4
, a light-emitting layer
5
, a p-type clad layer
6
and a p-type contact layer
7
successively deposited on an insulating substrate
1
, and also has a p-type electrode
9
formed on the deposited layers. The grown film is partially etched away through to a portion of n-type contact layer
3
and an n-type electrode
68
is formed thereon.
FIG. 35
is a perspective view of a laser diode device as another example of conventional group III-V type nitride compound semiconductor devices, with application of the technique of etching a grown film to form an electrode in a proximity of a substrate.
The laser diode device shown in
FIG. 35
has n-type contact layer
3
, n-type clad layer
4
, an active layer
35
with a quantum well structure, p-type clad layer
6
and p-type contact layer
7
successively deposited on insulating substrate
1
, and also has p-type electrode
9
formed on the deposited layers. The grown film is partially etched away through to a portion of n-type contact layer
3
, and an n-type electrode
78
is formed thereon.
FIG. 36
schematically shows a flow of current when current flows in a conventional semiconductor device in such a structure.
The semiconductor device shown in
FIG. 36
has substrate
1
, n-type contact layer
3
, n-type clad layer
4
, an active layer
5
, p-type clad layer
6
, p-type contact layer
7
, an n-type electrode
88
and p-type electrode
9
. As shown in
FIG. 36
, the flow of current in the conventional semiconductor device thus structured is biased to n-type electrode
88
. Accordingly, when the device is particularly applied as a light emitting device, the luminous efficiency is degraded. The semiconductor device shown in
FIG. 36
also has two electrodes
88
and
9
at a same side with respect to substrate
1
and thus the chip size is disadvantageously increased.
As another example of the technique of forming an electrode in a proximity of a substrate, Japanese Patent Laying-Open No. 7-221347 discloses that a substrate is partially removed to expose a surface of a gallium nitride based compound semiconductor layer and an electrode closer to the substrate is formed on the exposed, gallium nitride based compound semiconductor layer.
FIG. 37
is a cross section of a light emitting diode device as still another example of conventional group III-V type nitride compound semiconductor devices, with application of the technique of partially removing a substrate to expose a gallium nitride based compound semiconductor layer and forming an electrode in a proximity of the substrate on the exposed semiconductor layer.
The light emitting diode device shown in
FIG. 37
has an n-type gallium nitride based compound semiconductor layer
94
and a p-type gallium nitride based compound semiconductor layer
96
successively deposited on sapphire substrate
1
, and also has a positive electrode
99
on the deposited layers. Sapphire substrate
1
is partially removed so that the removal reaches n-type gallium nitride based compound semiconductor layer
94
, to expose n-type gallium nitride based compound semiconductor layer
94
. A negative electrode
98
is formed in contact with the exposed n-type gallium nitride based compound semiconductor layer
94
.
A semiconductor device thus structured can solve the disadvantageous increase in chip size as with application of the technique disclosed in Japanese Patent Laying-Open No. 8-17803.
For the technique of partially etching a substrate away to form an electrode, however, the electrode closer to the substrate has a reduced area. Accordingly, current is not uniformly injected into the light emitting layer. While the area of the portion to be etched away can be increased to increase the area of the electrode, the mechanical strength of the substrate material is practically degraded and thus the area of the electrode closer to the substrate cannot be so increased. As a result, the operating voltage of the semiconductor device is disadvantageously increased.
SUMMARY OF THE INVENTION
One object of the present invention is to solve the aforementioned disadvantages and provide a group III-V type nitride compound semiconductor device superior in characteristics and a method of simply manufacturing the same.
A group III-V type nitride compound semiconductor device in one aspect of the present invention has an insulating substrate, a metal nitride layer of a conductivity formed on a first surface of the insulating substrate, and a group III-V type nitride compound semiconductor layer formed on the metal nitride layer. The insulating substrate has an opening at a portion thereof, and also has a first electrode formed in contact with the metal nitride layer at the opening, and a second electrode formed on the group III-V type nitride compound semiconductor layer.
In one aspect of the present invention, the metal nitride layer preferably consists of any of nitrides of any element which belongs to the groups
3
A,
4
A,
5
A and
6
A in the periodic table.
More specifically, the metal nitride layer contains at least one material selected from the group consisting of CeN, CrN, DyN, ErN, EuN, GdN, HoN, LaN, LuN, NbN, NdN, PrN, PuN, ScN, SmN, TbN, ThN, TiN, TmN, UN, VN, YN, YbN and ZrN.
In one aspect of the present invention, the insulating substrate is preferably of an oxide material selected from the group consisting of MgO, LiGaO
2
, LiAlO
2
, ZnO, LiMgO
3
and Al
2
O
3
.
In one aspect of the present invention, the group III-V type nitride compound semiconductor layer preferably includes a first contact layer of a first conductivity formed on the metal nitride layer, a first clad layer of the first conductivity formed on the first contact layer, a light emitting layer formed on the first clad layer, a second clad layer of a second conductivity formed on the light emitting layer, and a second contact layer of the second conductivity formed on the second clad layer.
In one aspect of the present invention, preferably the group III-V type nitride compound semiconductor device is applied as a light emitting diode device and the metal nitride layer is formed to cover the entirety of a first surface of the insulating substrate.
More preferably, the device is also provided with a second metal nitride layer formed
Baumeister B. W.
Jackson, Jr. Jerome
Morrison & Foerster / LLP
Sharp Kabushiki Kaisha
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