Abstract
GaN-based semiconductor materials play an important role for high power and high speed device and circuit applications. Compared with Si, GaN has higher breakdown field and electron drift velocity, which make GaN-based devices an excellent candidate for such applications. This dissertation focuses on the design and fabrication of high performance GaN-based devices with high breakdown voltage, high operation speed and low on resistance. In this study, we realize high voltage AlGaN/GaN HEMTs with low on-resistance and over 600 V breakdown voltage. We also demonstrate 700-V AlGaN/GaN Schottky diodes which show a fast reverse recovery of only 15 ns. In addition, we propose a new process flow for GaN HEMTs to minimize the off-state leakage. The oxide-filled isolation followed by post-gate treatment reduces the off-state leakage by more than three orders of magnitude compared with conventional devices. An off-state drain leakage current smaller than 1e-9 A/mm and an excellent ON/OFF current ratio up to 1.5e8 can be achieved. We also demonstrate the first InN/AlN HFET with gate-controllable characteristics. Owning to the high sheet carrier density, a high current density up to ~530 mA/mm is achieved in a device with a 5-um gate length and a width of 100um, which is much higher than that in conventional GaN-based devices.