Characterizations of Mg-doped GaN Thin Films Grown by MetalOrganic Chemical Vapor Deposition System

• Main Authors: Yi-Chun Lin, 林逸峻
• Other Authors: San-Mao Liao
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/57433801587685335505

碩士 === 中原大學 === 電子工程研究所 === 89 === Abstract Until now, GaN and its related materials are the key issue for developing the blue-green devices. In this thesis , the investigation magnesium doped GaN films with various Cp2Mg flow rate and growth temperature was conducted in atmospheric pressure metalorganic chemical vapor deposition(AP-MOCVD). The optical, electrical and physical characteristics were analyzed and measured using room temperature photolumiscence(PL), Hall-measurement and XRD, respectively. Experimental data indicate that the photoluminescence peak wavelength and carrier concentration varies in different Cp2Mg flow rate. The crossover from n-type to p-type conduction occurs approximately at 1.9% of [Mg]/[Ga] mole flow ratio . Below the critical value , the Mg-doped GaN thin films show n-type conductivity. In opposites , above the specified ratio of 1.9% reveals p-type conduction, which is intimately related to the Cp2Mg molar fraction. Photoluminescence data reveals that two dominant peaks appear with increasing Cp2Mg flow rate. At low Cp2Mg flow rate shows a conduction band to acceptor (eA) transition peaked at 382nm. While the more magnesium is doped, a broader blue feature of 430nm wavelength is eventually observed. It is suggested, that associated with a DAP transition involving with deep donors introduced by the high concentration of magnesium solid incorporation. The GaN growth rate becomes slow with increasing growth temperature, although Mg doping efficient is independent of the growth temperature. The highly added magnesium dopants are introduced into GaN film, leading to relative vacancies and crystalline defects, that consequently degrade the thin film quality and decrease hole concentration . As a whole, the incorporation of optical, electrical and physical properties will help us to improve the crystalline characterizations of GaN thin films and to enhance the performance of the relevant nitride-based devices.