| AlGaN/GaN heterostructure field-effect transistors (HFETs) have been an exciting area for high temperature, high frequency, and high power applications beyond that of silicon and GaAs based devices. However, the gate leakage current of the HFET is too high and reduces its potential in many applications. GaN metal-oxide semiconductor field-effect transistors (MOSFET), on the other hand, can amazingly decrease the gate leakage current, but the device saturation current and power performance are too poor for practical applications.; The purpose of this study is to fabricate a novel AlGaN/GaN MOS-HFET device to significantly reduce the gate leakage current. It is also aimed at increasing the MOS-HFET DC and microwave performance to values similar to that of the best HFETs. This dissertation reports the first high performance AlGaN/GaN MOS-HFET in the world with SiO2 as the gate insulator. It is also the first to report an AlGaN/GaN multi-finger MOS-HFET with SiO 2 as the dielectric bridge material. The MOS-HFET devices, with SiO 2 as the gate insulator, demonstrate high performance comparable or even better than that of HFETs at temperatures up to 300°C. The gate leakage current of the MOS-HFET is six orders lower than that of an HFET. To increase the device output power, multi-finger HFET and MOS-HFET devices are designed and fabricated. With the thick SiO2 passivation, the AlGaN/GaN MOS-HFET breakdown voltage was increased from 500V to 600V. The device performance of the AlGaN/GaN MOS-HFET is also improved with Si3N4 as the gate insulator, compared with that of the MOS-HFET with SiO2 as the gate insulator. The MOS-HFET device performance is greatly improved with the submicron gate technology.; The results of this study demonstrate the high performance of the novel AlGaN/GaN MOS-HFET, combining the advantages of the MOSFET and the HFET. |
