METHOD OF FABRICATING SEMICONDUCTOR LIGHT EMITTING DEVICE SUBSTRATE
A method of fabricating a substrate for semiconductor light emitting devices is provided. The method includes forming a nanocrystal structure on a surface of the substrate which is a single crystal material, wherein the nanocrystal structure has an etched region and an unetched region. Next, a nitride semiconductor material is grown on the surface of the single crystal material with an epitaxial process, so as to form a substrate. Due to the periodicity of the nanocrystal structure, the semiconductor material grown on the substrate has fewer defects, and the material stress is reduced. Besides, the nanocrystal structure is capable of diffracting an electromagnetic wave, such that a higher light emitting efficiency and a higher output power may be obtained accordingly.
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This application is a divisional of an application Ser. No. 11/470,620, filed on Sep. 6, 2006, now allowed, which claims the priority benefit of Taiwan application serial no. 95121557, filed on Jun. 16, 2006. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor light emitting device. More particularly, the present invention relates to a method of fabricating a semiconductor light emitting device having a nanocrystal structure.
2. Description of Related Art
Distinct from the light emitting theory of regular fluorescent lamps or incandescent lamps generating heat to emit light, semiconductor light emitting devices such as light emitting diodes takes advantage of the specific property of semiconductor to emit light, and thus the light emitted by light emitting diodes is referred to as cold luminescence. The light emitting diodes have advantages of long service life, light weight, and low power consumption, and being free of harmful substance such as mercury, so the light emitting diodes used instead to illuminate can save a large amount of energy.
Currently, a nanocrystal light emitting diode is proposed to improve the light emitting diode. Researchers found that like the frequency band structure in the state of electromagnetic wave being transmitted in periodic dielectric, a photonic band substance can be achieved by the periodic changing of more than two kinds of materials with different refraction index (or dielectric constant), thereby paving a way for developing the above nanocrystal light emitting diode.
Referring to
The nanocrystal mainly functions as changing the refraction of light, such that the light emitted from the active light emitting layer can be successfully sent out, and is not totally reflected inside the light emitting diode. Therefore, the nanocrystal light emitting diode has higher extraction efficiency than the conventional light emitting diode.
However, the pattern 104a (i.e., the nanocrystal structure) of the P-type GaN layer 104 is usually fabricated in manner of etching, such that the defect density at the etched portions increases, leading to the increase of resistance, thus influencing the electrical property of the light emitting diode.
SUMMARY OF THE INVENTIONThe present invention is related to a method of fabricating a semiconductor light emitting device substrate. By the use of the semiconductor light emitting device substrate, a light emitting device formed thereon can obtain a higher light emitting efficiency and a higher output power accordingly.
Furthermore, the present invention is related to a method of fabricating a semiconductor light emitting device substrate, which can decrease the defect and stress of the semiconductor light emitting device grown on the substrate.
With the foregoing advantages that the semiconductor light emitting device substrate can achieve according to the present invention, there is provided a method of fabricating a semiconductor light emitting device substrate, which comprises providing a single crystal material. Next, a nanocrystal structure is formed on a surface of the single crystal material, wherein the nanocrystal structure has an etched region and an unetched region. Next, a nitride semiconductor material is grown on the surface of the single crystal material with an epitaxial process, so as to form a substrate.
Because to the periodic nanocrystal structure is disposed on the surface of the substrate, the structure formed according to the present invention has the following advantages. (1) The semiconductor material grown on the substrate has fewer defects. (2) The semiconductor light emitting device grown on the substrate has higher light emitting efficiency. (3) The semiconductor light emitting device grown on the substrate has higher optical output power. (4) The material stress of the semiconductor light emitting device grown on the substrate is reduced.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Referring to
Referring to
The geometric pattern as shown in
Referring to
The substrate of the first embodiment can be directly applied in all commonly-used blue, green, and white light emitting diodes. A semiconductor light emitting device fabricated by the use of the substrate of the first embodiment of the present invention is illustrated with reference to an embodiment below. However, it is not intended to limit the application scope of the present invention.
Referring to
Referring to
The substrate 200 has the nanocrystal structure 210, so the semiconductor light emitting device fabricated by the use of the substrate 200 has higher optical output power and higher light emitting efficiency. Particularly, when the semiconductor light emitting device is applied in a flip-chip process, the extraction efficiency can be further improved.
Referring to
A semiconductor light emitting device fabricated by using the substrate of the second embodiment of the present invention is illustrated with reference to the embodiment below. However, it is not intended to limit the application scope of the present invention.
Referring to
The substrate 800 has a periodic nanocrystal structure 810, so with the lateral overgrowth property in the epitaxial growth, the grown undoped nitride semiconductor layer 806 has fewer defects. In addition, due to the nanocrystal structure 810, the semiconductor light emitting device fabricated on the substrate 800 has higher optical output power and higher light emitting efficiency. Particularly, when the semiconductor light emitting device is applied in the flip-chip process, the extraction efficiency can be further improved.
To sum up, the substrate of the present invention has a periodic nanocrystal structure on the surface, so the defect of the semiconductor material grown on the substrate may be reduced during the epitaxial process, and the material stress of the semiconductor light emitting device grown on the substrate can also be reduced. In addition, due to the inherent advantages of the nanocrystal, the semiconductor light emitting device fabricated on the substrate has higher optical output power and higher light emitting efficiency. Furthermore, the light emitting diode formed on the substrate of the present invention does not have the pattern 104a (i.e., the nanocrystal structure) as shown in
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.
Claims
1. A method of fabricating a semiconductor light emitting device substrate, comprising:
- preparing a single crystal material;
- forming a nanocrystal structure on a surface of the single crystal material, the nanocrystal structure having an etched region and an unetched region, wherein the etched region has a depth of 10-200 nm, and
- growing a nitride semiconductor material on a surface of the single crystal material by performing an epitaxial process to form a substrate.
2. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein a material of the substrate is transmissive and does not absorb light in the wavelength range of visible light and infrared light.
3. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein the single crystal material comprises Al2O3, LiAlO2, LiGaO2, SiC, GaN, AlN, or AlGaN.
4. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein the step of forming the nanocrystal structure comprises:
- defining a pattern on the surface of the single crystal material by performing a lithographic process; and
- performing an etching process on the surface of the single crystal material to form the nanocrystal structure.
5. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 4, wherein the etching process comprises dry etching or wet etching.
6. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 4, wherein the lithographic process comprises laser interference lithography, holography-lithography, E-beam lithography, X-ray lithography, nano lithography, or nano imprinting.
7. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 4, wherein the pattern is a periodically arranged geometric pattern, the periodic structure has a plurality of crystals with a size of 100-900 nm, and each of the crystals has a quadrilateral-shape, a pentagon-shape, a hexagon-shape, or a polygon-shape.
8. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein the geometric pattern comprises at least a periodic pattern of tetragonal lattice or hexagonal lattice.
9. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein the epitaxial process comprises MBE, MOCVD, OMVPE, HVPE, PECVD, or sputter.
10. The method of fabricating the semiconductor light emitting device substrate as claimed in claim 1, wherein the nitride semiconductor material comprises In, Al, or Ga.
Type: Application
Filed: Jul 30, 2008
Publication Date: Dec 11, 2008
Applicant: INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE (Hsinchu)
Inventors: Chang-Cheng Chuo (Hsinchu County), Chih-Ming Lai (Pingtung County)
Application Number: 12/183,058
International Classification: H01L 33/00 (20060101);