AlGaN/GaN high electron mobility transistors(HEMTs)with high performance were fabricated and characterized.A variety of techniques were used to improve device performance,such as AlN interlayer,silicon nitride passivation,high aspect ratio T-shaped gate,low resistance ohmic contact and short drain-source distance. DC and RF performances of as-fabricated HEMTs were characterized by utilizing a semiconductor characterization system and a vector network analyzer,respectively.As-fabricated devices exhibited a maximum drain current density of 1.41 A/mm and a maximum peak extrinsic transconductance of 317 mS/mm.The obtained current density is larger than those reported in the literature to date,implemented with a domestic wafer and processes.Furthermore, a unity current gain cut-off frequency of 74.3 GHz and a maximum oscillation frequency of 112.4 GHz were obtained on a device with an 80 nm gate length. A variety of techniques were used to improve device performance, such as AlN interlayer, silicon nitride passivation, high aspect ratio T-shaped gate, low resistance ohmic contact DC and RF performances of as-fabricated HEMTs were characterized by utilizing a semiconductor characterization system and a vector network analyzer, respectively. As-fabricated devices exhibited a maximum drain current density of 1.41 A / mm and a maximum Peak extrinsic transconductance of 317 mS / mm. The resulting current density is larger than those reported in the literature to date, implemented with a domestic wafer and processes. Future plus, a unity current gain cut-off frequency of 74.3 GHz and a maximum oscillation frequency of 112.4 GHz were obtained on a device with an 80 nm gate length.