Growth and optoelectronic characterizations of ultrananocrystalline diamond thin film on Ⅲ-nitride based light-emitting diode

• Main Authors: Chia-Yu Liao, 廖家鈺
• Other Authors: Wen-Cheng Ke
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/j22x82

碩士 === 國立臺灣科技大學 === 材料科學與工程系 === 107 === LED devices are moving toward thin, small size and high brightness. If you want to achieve high brightness by injecting high current into the wafer, the operating temperature will increase. The high operating temperature decreases the life time of LED devices. In this study, ultrananocrystalline diamond (UNCD) thin films, which are thermal stable, are grown on gallium nitride (GaN) as an electrode and study its growth and photoelectronic properties. The un-doped UNCD and N-doped UNCD growth parameters are optimized respectively. The optical emission spectroscopy (OES) indicates that the characteristic peaks at 472, 516 and 563 nm for C2 radical generated in CH4/Ar plasma. The Raman spetrum indicates the two step deposition of UNCD, which the graphite buffer layer should be deposited on GaN thin films first and then UNCD grows on that. The UNCD could be deposited when the chamber pressure might be higher than 80 torr. The OES of CH4/N2/Ar plasma indicates additional CN characteristic peak at 387 nm and 421 nm. The N-doped UNCD thin films are analyzed by Raman spectroscopy and the result indicates that adding N2 in CH4/Ar plasma could increase the concentration of sp2 carbon atoms in the thin films. The resistivity of N-doped UNCD thin films could be decreased to about 2× 106 Ω·cm by adding 15 sccm N2. Then, N-doped UNCD thin films are directly deposited on LED as an electrode. The electroluminescence (EL) spectrum of LED are finished with applying 30-90 mA, and the highest luminance of LED are found with applying 80 mA. The wavelength of luminance is 458.4 nm and FWHM is 20.94 nm. The EL spectrum of LED confirms the emissivet layer in LED is not be damaged during the process of growth N-doped UNCD.