Recent Advances in GaN‐Based Power HEMT Devices

Abstract 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.