Optimization of GaN and AlN epilayer for HEMT application

• Main Authors: Lee, Yuan-Jyun, 李元鈞
• Other Authors: Chou, Wu-Ching
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/m3an56

碩士 === 國立交通大學 === 電子物理系所 === 106 === GaN, Al1-xGaxN, and AlN epilayers were grown by molecular beam epitaxy system (MBE). The in situ reflection high-energy electron diffraction (RHEED) measurements were used to find the best growth conditions of substrate temperature and element flux ratio. The optical properties and surface morphology were analyzed by photoluminescence (PL), cathodoluminescence (CL), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, the electrical properties of two dimensional electron gas (2DEG) of AlN/GaN heterostructure were investigated by the Hall measurements. By the control of substrate temperature and Ga/N ratio, the luminescence signal from Ga vacancy could be suppressed and a better surface roughness about 0.4 nm for GaN was achieved. In the case of Al1-xGaxN growth, the substrate temperature was fixed at 740 oC for high Al composition samples. By using the migration enhanced epitaxy (MEE) for the interface expitaxy of AlN/GaN heterostructure, the decomposition of GaN channel layer can be significantly suppressed. The raising substrate temperature to 740 oC enhances migration of the AlN to fill the surface pits. It improves the electron mobility up to 988 (cm2/V•s) in 2DEG.