Study of AlGaN/GaN Metal-Oxide-Heterostructure FET with a Liquid Phase Deposited Oxide as Gate Dielectric

• Main Authors: Shun-Kuan Lin, 林舜寬
• Other Authors: Yeong-Her Wang
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/98337952195127127988

碩士 === 國立成功大學 === 電機工程學系碩博士班 === 92 === 　　An efficient and low cost approach for depositing uniform silicon dioxide layers on GaN by liquid phase deposition (LPD) that is near room temperature will be described. The deposited rate of SiO2 is about 55nm/hr. at 40 ℃. Breakdown electric field as high as 7.3MV/cm and leakage current as low as 10-7A/cm2 at 0.9MV/cm for the deposited oxide layers can be achieved. The trap density of SiO2 on GaN or AlGaN is about 3×1011cm2eV-1. Auger Electron Spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) will be used to characterize the oxide properties. Self-align and self- passivation process of LPD can ease the device fabrication. AlGaN/GaN metal oxide semiconductor heterostructure field effect transistors (MOSHFETs) with liquid phase deposited SiO2 as the gate dielectric will be demonstrated. Ti/Al/Au (80nm /100nm/130nm) with a specific contact resistance of 2.17*10-5 Ω-cm2 can be achieved for source/drain ohmic contacts. Photo electrochemical wet etching with K2S2O8 (peroxydisulfate) as the oxidizing agent instead of the platinum electrode is used for device isolation. The best transconductance of AlGaN/GaN MOSHFET for gate length of 2um with 100um long in width is about 53 mS/mm at Vgs=-4V, Vds=12V and the maximum drain saturation current is 650 mA/mm. Comparison between the AlGaN/GaN MOSHFETs and heterostructure field effect transistors (HFETs) will also be made. Lower leakage current and larger gate swing voltage and flatter transconductances range can be seen in MOSHFETs.