| Over the last decade, significant and rapid advances in epitaxial growth of gallium nitride (GaN) and related wide bandgap materials have yielded exciting developments. Both optical and electronic devices have been demonstrated. Light-emitting and laser diodes operating at various short wavelengths have been shown to be very reliable and are now commercialized. Also, due to excellent electronic properties such as high critical breakdown field, high saturation and overshoot electron velocities, and good thermal conductivity GaN-based transistors are ideal for high-power and high-temperature applications. Transistors based on nitride materials can operate at high speeds, at high power levels, at high temperatures (300--600°C), and also in very harsh (i.e., corrosive or high radiation) environments. AlGaN/GaN high electron mobility transistors (HEMTS) producing high bandwidth and record microwave powers have been demonstrated. GaN-based electronic devices for microwave, high-power, and high-temperature applications are expected to be commercialized soon.; In this work, the development of fabrication process and transistor designs for high-performance AlGaN/GaN HEMTS required for high-power applications are presented. Three transistor designs under study are a gate-recessed HEMT, asymmetric HEMT with varying gate-drain spacing, and field-plate HEMT. Each transistor design offers a trade-off between microwave and DC characteristics as the key design parameter is varied. The knowledge of this trade-off is crucial in the design of AlGaN/GaN HEMTS. Dependence of DC, microwave and large signal performance on design parameters is presented so that the trade-off between DC and microwave characteristics can be established, which will facilitate the optimization of AlGaN/GaN HEMT design for high-power applications. This work contributes to the developmental research in the field of GaN-based FETs. |
