A light emitting device such as a light emitting diode (LED) is a kind of a P-N junction diode and is a semiconductor device using an electroluminescence which is a monochromatic light emitting phenomenon when a voltage is applied to forward direction. The wavelength of the light emitted from the light emitting device is determined by the badgap energy (Eg) of a material used. At the beginning of the light emitting device technique, light emitting devices capable of emitting infrared and red light have been developed. Researches on a blue LED has begun in full-scale after founding that a blue light might be generated when using GaN by Nakamura at Nichia Chemistry in 1993. Since white light may be obtained through combining red, green and blue, the development on the GaN-based blue light emitting device along with already developed red and green light emitting devices, enabled the accomplishment of a while light emitting device.
Recently, as the demand on the blue wavelength light emitting device increases, the demand on a GaN thin film is also increased from day to day. In order to increase the efficiency of the light emitting device, various methods have been used.
Among the methods, an epitaxial lateral overgrowth (ELO) method is used to manufacture a nitride semiconductor thin film having high quality and determining inner quantum efficiency. However, the ELO method required complicated processes and a long processing time, including the growth of a buffer layer by an MOCVD method, etc., transferring the buffer layer to an SiO2 deposition apparatus to form an SiO2 thin film, forming an SiO2 pattern by a photolithographic etching process, and inserting into the MOCVD reacting apparatus again to grow a GaN layer.
In addition, since a substrate of the same kind as the GaN thin film is absent, a stress may be generated due to a lattice discrepancy between the GaN thin film and the substrate.