Recent Advances in GaN-Based Power HEMT Devices

The ever-increasing power density and operation frequency in electrical power conversion systems require the development of power devices that can outperform conventional Si-based devices. Gallium nitride (GaN) has been regarded as the candidate for next-generation power devices to improve the conversion efficiency in high-power electric systems. GaN-based high electron mobility transistors (HEMTs) with normally-off operation is an important device structure for different application scenarios. In this review, an overview of a series of effective approaches to improve the performance of GaN-based power HEMT devices is given. Modified epistructures are presented to suppress defects and current leakage, and low-damage recess-free processes are discussed in fabricating normally-off HEMTs. Possible effects of dielectrics on a metal-insulator-semiconductor (MIS) structure are also intensively introduced. Metal/semiconductor contact engineering is investigated, and fabrication of Au-free ohmic contact and graphene insertion layer to enhance the device performance is emphasized. Finally, the effects of field plates are studied through the use of simulated and fabricated devices.