Active solid-state devices (e.g. – transistors – solid-state diode – Incoherent light emitter structure – With reflector – opaque mask – or optical element integral...
Reexamination Certificate
2000-01-10
2004-02-24
Flynn, Nathan J. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Incoherent light emitter structure
With reflector, opaque mask, or optical element integral...
C257S079000, C257S094000, C257S099000, C257S100000, C257S103000
Reexamination Certificate
active
06696704
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a composite light-emitting device including a light-emitting element such as light-emitting diode or laser diode, which is implemented as multiple semiconductor layers stacked on a transparent substrate, and a resin member. The resin member may contain a photofluorescent compound that shifts the wavelength of the radiation emitted from the light-emitting element or a filtering compound that partially absorbs the radiation. The present invention also relates to a semiconductor light-emitting unit including the composite light-emitting device and to a method for fabricating the same.
A technique of shifting the wavelength of radiation emitted from a light-emitting element using some phosphor has been well known in the art. For example, according to a technique, the inner wall of a glass neon tube is coated with a phosphor, thereby changing orange light into green one. As an alternative, a photofluorescent compound is added into a molding resin compound for a gallium arsenide (GaAs) light-emitting diode (LED) to convert red emission into green one. Recently, a white LED lamp, which emits white light by coating a blue-light-emitting diode of a Group III nitride semiconductor like gallium nitride (GaN) with a photofluorescent compound, was put on the market. In this specification, such an LED will be simply referred to as a “GaN LED”.
Hereinafter, a prior art white LED lamp will be described with reference to the accompanying drawings.
FIG. 14
illustrates a cross-sectional structure of a conventional white LED lamp. As shown in
FIG. 14
, the lamp includes: a first leadframe
100
A, which is provided with a reflective cup
100
a
at the end; and a second leadframe
100
B, the end of which is spaced apart from that of the reflective cup
100
a
. A GaN LED
110
is bonded onto the bottom of the reflective cup
100
a
with an insulating adhesive
101
. One of the electrodes of the GaN LED
110
is connected to the first leadframe
100
A with a first wire
102
A, while the other electrode thereof is connected to the second leadframe
100
B with a second wire
102
B. The reflective cup
100
a
is filled in with a wavelength-shifting resin medium
104
, which contains a photofluorescent compound that shifts the wavelength of the radiation emitted from the GaN LED
110
, so as to cover the GaN LED
110
. The upper ends of the first and second leadframes
100
A and
100
B, as well as the reflective cup
100
a
, are molded together within a spherical resin encapsulant
105
such as transparent epoxy resin to form the white LED lamp.
Although not shown in any drawing, a chip LED may also be formed without using the reflective cup
100
a
or the spherical resin encapsulant
105
. In the chip LED, the GaN LED
110
is mounted onto a concave receptacle within a casing and then the gap between the LED
110
and the receptacle is filled in with a resin encapsulant containing a photofluorescent compound to secure them together.
Next, a detailed construction of the known GaN LED
110
will be described.
FIGS.
15
(
a
) and
15
(
b
) illustrate the GaN LED for use in the conventional white LED lamp: FIG.
15
(
a
) illustrates a planar layout thereof; and FIG.
15
(
b
) illustrates a cross-sectional structure thereof taken along the line XVb—XVb in FIG.
15
(
a
). As shown in FIG.
15
(
b
), the GaN LED
110
includes n-type GaN contact layer
112
, quantum well structure and p-type GaN contact layer
116
, which are stacked in this order over a sapphire substrate
111
. The quantum well structure is formed on part of the upper surface of the n-type contact layer
112
and includes n-type AlGaN first barrier layer
113
, InGaN single quantum well (SQW) layer
114
and p-type AlGaN second barrier layer
115
.
Also, as shown in FIG.
15
(
a
), an n-side electrode
117
is formed on the exposed part of the upper surface of the n-type contact layer
112
. A current-diffusing transparent electrode
118
is formed on the p-type contact layer
116
. And a p-side electrode
119
is formed on the transparent electrode
118
to be located farthest from the n-side electrode
117
.
Since the conventional GaN LED
110
is formed on the insulating sapphire substrate
111
, both the n- and p-side electrodes
117
and
119
are provided on the same side of the substrate
111
as that including the LED thereon.
The conventional white LED lamp shown in
FIG. 14
or the chip LED (not shown) covers the GaN LED
110
by filling in the reflective cup
100
a
or the receptacle of the casing with the wavelength-shifting resin medium
104
containing the photofluorescent compound
103
. Thus, the prior art construction is not applicable to a light-emitting unit including no such reflective cup
100
a
or receptacle.
Also, if the reflective cup
100
a
or receptacle should be filled in with the wavelength-shifting resin medium
104
, it is difficult to precisely control the amount of the resin medium to be filled in or the variation in concentration of the photofluorescent compound
103
. Thus, the chromaticity changes significantly. As a result, the yield of good light-emitting units with a desired chromaticity decreases.
Furthermore, the GaN LED
110
included in the white LED lamp or chip LED is the same as that included in a blue LED lamp. The blue-light-emitting diode is poorly resistant to static electricity due to the physical constants (like the relative dielectric constant ∈) of the constituent materials thereof or the structure thereof.
SUMMARY OF THE INVENTION
A first object of the present invention is getting a composite light-emitting device always covered with a wavelength-shifting resin medium irrespective the shapes of leadframes or casings.
A second object of the present invention is improving the resistance of a composite light-emitting device or semiconductor light-emitting unit to an overvoltage caused by static electricity.
A third object of the present invention is making the chromaticity of the emission finely adjustable while at the same time suppressing the variation in chromaticity.
To achieve the first object, an inventive composite light-emitting device includes a light-emitting element and a submount member. The light-emitting element with an active region defined on a transparent substrate is mounted facedown on the submount member with the active region of the light-emitting element facing the principal surface of the submount member. The submount member is electrically connected to the light-emitting element. And the light-emitting element is covered with a wavelength-shifting resin medium on the principal surface of the submount member.
To accomplish the second object, the submount member is implemented as an overvoltage protector.
To attain the third object, the light-emitting face of the substrate for the light-emitting element on the opposite side to its circuitry side and/or the outer surface of the wavelength-shifting resin medium above the light-emitting face are/is made parallel to the back surface of the submount member.
Specifically, a composite light-emitting device according to the present invention includes a light-emitting element including a transparent substrate and a multilayer structure formed on the substrate. The multilayer structure includes first and second semiconductor layers of first and second conductivity types, respectively. The device further includes a submount member for mounting the light-emitting element thereon. The principal surface of the submount member faces the multilayer structure. The submount member is electrically connected to the light-emitting element. The device further includes a wavelength-shifting resin member, which is provided on the principal surface of the submount member to cover the light-emitting element. The wavelength-shifting resin member contains a photofluorescent or filtering compound. The photofluorescent compound shifts the wavelength of radiation that has been emitted from the light-emitting element. The filtering compound partially absorbs the radiation.
In the c
Inoue Tomio
Maeda Toshihide
Obara Kunihiko
Flynn Nathan J.
Matsushita Electric - Industrial Co., Ltd.
Mondt Johannes
Nixon & Peabody LLP
Studebaker Donald R.
LandOfFree
Composite light-emitting device, semiconductor... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite light-emitting device, semiconductor..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite light-emitting device, semiconductor... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3339337