| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系所 === 104 === The integration of GaN-based High Electron Mobility Transistors (HEMTs) and a large diameter Si substrate are promising candidates for next-generation high power device applications owing to the high current, high breakdown, and low fabrication cost. This thesis focuses GaN-based HEMTs on Si with low current collapse by high quality gate insulator and development of gold free gate structure with high thermal stability. First of all, the stable electrical properties of Al2O3/AlN/AlGaN/GaN metal-insulator-semiconductor (MIS-HEMTs) by using an Al2O3/AlN stack layer as the gate insulator layer were investigated. The device exhibits a small threshold voltage hysteresis of ~200mV. Additionally, no obvious changes in the drain current were observed for the device during the drain voltage stress of 100V for 15 h. Secondly, a gate recessed normally-OFF Al2O3/AlN/AlGaN/GaN MIS-HEMT with low threshold voltage hysteresis is demonstrated. The device exhibits a threshold voltage of +1.5 V, with current density of 420mA/mm, an OFF-state breakdown voltage of 600V and high ON/OFF drain current ratio of ~109. Finally, a GaN HEMT with WNX/Cu gate for high power application is developed. The direct current (DC) characteristics of the device are comparable to a conventional Ni/Au gated GaN HEMT. The results of a high voltage stress test indicated that the device was stable after 200 V stress was applied for 42 hours. Additionally, the WNX/Cu gated GaN HEMTs exhibits no obvious change for DC characteristics and Schottky barrier height before and after 2500C annealing for 1 hour.
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