Semiconductor device manufacturing: process – Making device or circuit emissive of nonelectrical signal – Including integrally formed optical element
Reexamination Certificate
2001-09-19
2002-10-01
Thompson, Craig (Department: 2813)
Semiconductor device manufacturing: process
Making device or circuit emissive of nonelectrical signal
Including integrally formed optical element
Reexamination Certificate
active
06458612
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for forming high efficiency light-emitting diode (LED), and more particularly, to a method for fabricating high efficiency light-emitting diode adhered to a transparent substrate, such as the material of glass.
BACKGROUND OF THE INVENTION
A light-emitting diode (LED) is an important optoelectronic device which is widely used in various products such as electronic devices, advertising signs and electrical appliance to indicate the related messages or to sharpen the beauty of a product. Additionally, the utilization of the LEDs has been gradually expanding to all kinds of application. The high brightness becomes a significant index level of the superior quality LEDs besides true color and duration of the LEDs.
Referring to
FIG. 1A
, GaAs is used as a semiconductor substrate for the LEDs. To begin with, a double heterostructure
110
is formed on a GaAs substrate
10
wherein the double heterostructure
110
comprises a N-type cladding layer of AlGaInP
11
, an active layer of AlGaInP
12
and a P-type cladding layer of AlGaInP
13
, and a transparent layer
14
on the P-type cladding layer of AlGaInP
13
. Since the energy band gap of the GaAs substrate
10
is less than that of the active layer of AlGaInP
12
, the energy band gap of the GaAs substrate
10
lies in the range of the visible light. Consequently, the specific wavelengths of visible light, induced from the double heterostructure
110
, may be absorbed by the GaAs substrate
10
which results in brightness degradation of the LED.
Referring to
FIG. 1B
, GaP is used as a semiconductor substrate for the LEDs. A double heterostructure
110
is formed on a GaP substrate
15
wherein the double heterostructure
110
comprises a N-type cladding layer of AlGaInP
11
, an active layer of AlGaInP
12
and a P-type cladding layer of AlGaInP
13
, and a transparent layer
14
on the P-type cladding layer of AlGaInP
13
. Since the GaP may induce a light-emitting absorption in the range of spectrum (yellow and green), the conventional material is no more than applied to the use of some particular wavelength of LED.
Referring to
FIG. 2
, a Bragg reflector is applied on a GaAs semiconductor substrate. A Bragg reflector
21
formed on the GaAs substrate
10
and the double heterostructure
110
is formed on a GaAs substrate
20
wherein the double heterostructure
110
comprises an N-type cladding layer of AlGaInP
11
, an active layer of AlGaInP
12
and a P-type cladding layer of AlGaInP
13
, and a transparent layer
14
. The material of the Bragg reflector
21
is GaAs/AIAs having a coefficient 3.4 Although the Bragg reflector
21
can partially eliminate the absorption of the light emitted from the double heterostructure
110
to prevent the light-emitting from being absorbed by the GaAs substrate
10
. Unfortunately, the Bragg reflector
21
may increase the complexity of the process and thus largely spend a great of epitaxy time during manufacture process. Also, the sufficient thickness of the Bragg reflector
21
is needed, even so, the Bragg reflector
21
can not completely solve the light-emitting absorption problem by the GaAs substrate
10
.
Consequently, a conventional method for fabricating a LED according to the above involves some disadvantages as follows: (a) the visible light, emitted from the double heterostructure, will be absorbed by the GaAs substrate and result in a great deal of the light-emitting efficiency reduction; (b) a conventional material, GaP compound material, for a transparent layer may incur the absorption of some specific wavelength band (yellow or green) so that the transparent layer is only used in the particular range of the spectrum; and (c) the Bragg reflector may obviouly increase the manufacturing time and the production cost, especially, when multiple Bragg reflector layers are used.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a new method of fabricating high efficiency light-emitting diode (LED) adhered to a transparent substrate, preferably a glass adhered thereon by heat and to overcome the drawback of the lower light-emitting efficiency regarding the conventional LED.
In the preferred embodiment of the present invention, to begin with, providing a semiconductor substrate is followed by forming an etching stopper, a first type ohmic contact layer, a double heterostructure and then a second ohmic contact layer. The double heterostructure comprises a N-type cladding layer of AlGaInP, an active layer of AlGaInP and a P-type cladding layer of AlGaInP. Afterwards, a transparent substrate, such as preferably glass, which is visible in the range of visible light, is adhered to the second ohmic contact layer and then the GaAs substrate is removed away. The first type cladding layer and the undoped active layer are etched, wherein the second type ohmic contact layer is used as the etching stopper. The first electrode is formed on the first type ohmic contact layer and the second electrode is formed on the second type ohmic contact layer, respectively.
As a result, the present invention utilizes some features, for example, high transmittance and lower absorptivity, of the glass adhered to the second ohmic contact layer to visible light for increasing luminous intensity of the LED. Taking advantage of glass in strength and machining, the surface of the glass is easily roughed so that the total reflection inside the glass is entirely blocked while the photons are transmitted from the LED therethrough. Moreover, the absorption of the GaAs substrate for the visible light is significantly improved by appropriately decreasing the use of the GaAs material.
REFERENCES:
patent: 4442402 (1984-04-01), Besomi et al.
Chang Chih-Sung
Chen Tzer-Perng
Chiou Shu-Woei
Thompson Craig
United Epitaxy Company, Inc.
LandOfFree
Method of fabricating high efficiency light-emitting diode... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of fabricating high efficiency light-emitting diode..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of fabricating high efficiency light-emitting diode... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2928136