A platform for monolithic integration in GaN

The wide-bandgap semiconductor, Gallium Nitride (GaN), exhibits superior material characteristics which offer a promising solution to energy efficient power semiconductor applications. A high density polarization induced electron gas in a GaN based heterojunction with high mobility makes GaN field-effect-transistors (FETs) widespread in high frequency and high power technologies, to meet the requirements of massive data processing and continuously growing demand for energy. On-chip GaN complementary metal–oxide–semiconductor (CMOS) based logic by monolithic integration is a prospective way to eliminate degeneration of switching speed due to parasitic inductance and to realize the most energy efficiency topology with supressed static power dissipation, large noise immunity and improved scalability for the entire power switch system. However, the lack of a GaN p-channel device with high performance is a major obstruction to achieve this complementary technology. This thesis reveals a built-in potential barrier in a p-type Ohmic contact to a p-GaN/u-GaN/AlGaN/GaN based platform. A new composite back-to-back graded AlGaN barrier in GaN/AlGaN/GaN based epitaxial structure is utilized to provide a monolithic integration platform for simultaneously boosting the performance of both GaN n-FETs and p-FETs with normally-off operation. In addition, the characteristics of a power device in this platform are also improved by the back-to-back graded barrier compared to the counterpart in a conventional AlGaN barrier. Therefore, the back-to-back graded barrier is a strong candidate for power switching applications.