Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With heterojunction
Reexamination Certificate
2000-10-06
2003-04-22
Thomas, Tom (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With heterojunction
C257S095000, C257S096000, C257S097000, C438S022000, C438S048000
Reexamination Certificate
active
06552367
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Technical Field of the Invention
The present invention relates to a light emitting diode, and in particular, to a high brightness light emitting diode.
b) Description of the Related Art
In the U.S. Pat. No. 5,789,768 issued to Biing-Jye LEE et al. and having the same assignee as the present application, a light emitting diode as shown in
FIG. 1
is disclosed. In the light emitting diode, an n-type GaAs semiconductor substrate
12
is formed on an n-type back electrode
10
. A distributed Bragg reflector (DBR) layer
30
is formed on the semiconductor substrate
12
. The distributed Bragg reflector layer
30
preferably comprises a material chosen from the group consisting of AlGaInP and AlGaAs. A stacked structure
14
is formed on the reflector layer
30
and includes a bottom cladding layer of n-type AlGaInP
140
, an active layer of AlGaInP
142
, and a top cladding layer of p-type AlGaInP
144
. A p-type window layer
16
is formed on the top cladding layer
144
. The window layer
16
preferably comprises a material chosen from the group consisting of GaP, GaAsP, GaInP, and AlGaAs. A p-type contact layer
17
is formed on the window layer
16
. The contact layer
17
preferably comprises a material chosen from the group consisting of GaAsP, GaP, GaInP, and GaAs. A transparent conductive layer
19
is formed on the contact layer
17
, extends through the central hollow of the contact layer
17
, and contacts with the window layer
16
by forming a Shottky barrier therebetween. The transparent conductive layer
19
preferably comprises a material chosen from the group consisting of indium oxide, tin oxide, indium tin oxide, and the like transparent materials. A p-type front electrode
20
is formed on the conductive layer
19
.
The above mentioned prior art light emitting diode is characterized in that the contact surface between the conductive layer
19
and the contact layer
17
is formed into an ohmic contact and the contact surface between the conductive layer
19
and the window layer
17
is formed into a Shottky barrier. Therefore, after the current from the front electrode
20
is spread in the conductive layer
19
, it flows into the active layer through the ohmic contact and not through the Shottky barrier before it encounters the current from the back electrode
10
to generate light.
In the prior art light emitting diode, the current portion and the light emitting action directly under the front electrode
20
can be reduced because the current from the front electrode
20
can be controlled to flow through the ohmic contact and not through the Shottky barrier so that the undesired effect of blocking light by the front electrode
20
can be avoided. However, the light generated in the active layer
142
has to pass through the contact layer
17
to emit and the contact layer absorbs about 15% to 20% of the light passing therethrough. Besides, the interface between the contact layer
17
and the window layer
16
also causes an undesired effect of absorbing light. Consequently, if the area on which the contact layer
17
is located over the window layer
16
can reduced, the undesired effect of light absorbing by the contact layer
17
and by the interface between the contact layer
17
and the window layer can be reduced. Thereby, the brightness of the light emitting diode can be increased.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide a high brightness light emitting diode having a distributed contact area to reduce the undesired effect of light absorbing by the contact layer and by the interface between the contact layer and the window layer so that an improved efficacy of increasing the brightness of the light emitting diode can be achieved.
To achieve this object, a high brightness light emitting diode having a distributed contact area comprises a first electrode; a semiconductor substrate formed on the first electrode; a first cladding layer of a first conductivity type formed on the semiconductor substrate; an active layer formed on the first cladding layer; a second cladding layer of a second conductivity type formed on the active layer; a window layer of a second conductivity type formed on the second cladding layer; a distributed contact area in a predetermined pattern formed on the window layer; a transparent conductive layer formed over the distributed contact area and the window layer, the transparent conductive layer being in ohmic contact with the distributed contact area and a Shottky barrier being formed between the transparent conductive layer and the window layer; and a second electrode formed on the transparent conductive layer.
REFERENCES:
patent: 3889286 (1975-06-01), Debesis
patent: 5789768 (1998-08-01), Lee et al.
patent: 5814839 (1998-09-01), Hosoba
patent: 6057562 (2000-05-01), Lee et al.
patent: 49-137458 (1974-11-01), None
patent: 50-98796 (1975-08-01), None
patent: 57084188 (1982-05-01), None
patent: 10796602 (1998-09-01), None
Hsieh Min-Hsun
Jou Ming-Jiunn
Lee Biing-Jye
Epistar Corporation
Hsu Winston
Kang Donghee
Thomas Tom
LandOfFree
High brightness light emitting diode having a layer of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High brightness light emitting diode having a layer of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High brightness light emitting diode having a layer of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3053604