Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With housing or contact structure
Reexamination Certificate
1998-05-29
2001-02-20
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With housing or contact structure
C257S448000, C257S088000, C257S090000, C257S093000
Reexamination Certificate
active
06191438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light emitting diode array, and in particular to a light emitting diode array usable for data-back units of, for example, printer heads and cameras.
2. Description of the Related Art
A conventional light emitting diode array and a method for producing the same are disclosed in, for example, Japanese Laid-Open Publication No. 8-64864 filed by Sharp Kabushiki Kaisha and entitled “Light-Emitting Diode Array and Method for Fabricating the Same” (corresponding U.S. patent application Ser. No. 08/516,409). The light emitting diode array disclosed in the above-mentioned publication is shown in
FIGS. 7 through 10
.
FIG. 7
is a plan view of the conventional light emitting diode array. The light emitting diode array has seven light emitting elements
100
.
FIG. 8
is a plan view of one of the light emitting elements
100
, and
FIG. 9
is a cross-sectional view of the light emitting element
100
taken along lines IX—IX in FIG.
8
.
FIG. 10
is a partial isometric view of the light emitting diode array shown in
FIGS. 7 through 9
.
As best shown in
FIG. 9
, the light emitting element
100
includes an n-type GaAs substrate
50
, an n-type GaAs buffer layer
51
, an n-type Al
0.5
In
0.5
P cladding layer
52
, an undoped (Al
0.3
Ga
0.7
)
0.5
In
0.5
P active layer
53
, a p-type Al
0.5
In
0.5
P cladding layer
54
, and an Al
0.7
Ga
0.3
As current diffusion layer
55
. The layers
51
through
55
are sequentially provided on the n-type GaAs substrate
50
in this order and formed by MOCVD.
The light emitting element
100
further includes an insulative layer
56
provided on the current diffusion layer
55
. The insulative layer
56
is formed by forming an SiN
x
layer by plasma CVD on the current diffusion layer
55
and then performing photolithography and etching using buffered hydrogen fluoride. The insulative layer
56
is provided for preventing an electric current from being injected below a bonding pad
59
described below.
The light emitting element
100
further includes a p-side electrode
57
formed of a Ti/AuZn material and provided on the current diffusion layer
55
so as to cover the insulative layer
56
, an n-side electrode
58
formed of an AuGe/Ni material and provided on a rear surface of the substrate
50
, and the bonding pad
59
provided on the p-side electrode
57
preferably by sputtering Ti/Au. Red light mainly comes out from an area
155
of the current diffusion layer
55
on which the insulative layer
56
is not formed.
The conventional light emitting diode shown in
FIGS. 7 through 10
includes the current diffusion layer
55
in an area where it is not desirable to cause light to pass, namely, an area other than the area
155
. Accordingly, a light emission driving current expands through the current diffusion layer, and thus light passes an area where light passage is not desired. That is, the current diffusion layer acts as a light guide, thus causing light to pass an area where light passage is not desired. As a result, the light emitting point of each light emitting element is blurred.
SUMMARY OF THE INVENTION
A light emitting diode array according to the present invention includes a plurality of light emitting elements, provided on a substrate having a first conductivity type, for causing light to pass through a first area thereof. Each of the plurality of light emitting elements comprises an active layer; a first cladding layer having the first conductivity type and a second cladding layer having a second conductivity type provided so as to interpose the active layer therebetween; and a current diffusion layer having the second conductivity type. The current diffusion layers respectively included in the plurality of light emitting elements are isolated from one another, and an area including the current diffusion layer is included in the first area.
In one embodiment of the invention, each of the plurality of light emitting elements further comprises an insulative layer provided in contact with one of the active layer and the second cladding layer; an electrode provided on the insulative layer and electrically connected to the current diffusion layer; and an electrode pad provided on the electrode.
In one embodiment of the invention, the current diffusion layer has a mesa-shaped cross-section, and the electrode is provided so as to cover the entirety of a side surface of the current diffusion layer, the side surface facing the electrode pad.
In one embodiment of the invention, the active layer is formed of (Al
x
Ga
1−x
)
y
In
1−y
P (0≦x≦1, 0≦y≦1).
In one embodiment of the invention, the current diffusion layers of the plurality of light emitting elements are arranged substantially linearly.
Thus, the invention described herein makes possible the advantage of providing a light emitting diode array for improving the light emitting efficiency and offering a clear and sharp light emitting point by preventing light from propagating to an undesired area.
This and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.
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patent: 5744829 (1998-04-01), Murasato et al.
patent: 5753941 (1998-05-01), Shin et al.
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patent: 4-100278 (1992-02-01), None
patent: 5-327015 (1993-12-01), None
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patent: 8-64864 (1996-03-01), None
Ikehara Masahiro
Obana Takahiro
Jackson, Jr. Jerome
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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