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In this study, the device characteristics of dual-gate GaN high-electron-mobility transistors (HEMTs) were determined. The research investigated an enhancement-mode (E-mode) GaN HEMT with a second gate connected to the source and located between the main gate and drain. Two dual-gate GaN HEMTs with different second-gate designs, using Schottky or metal–insulator–semiconductor (MIS) contacts, were simulated and fabricated, and the direct current of the devices was investigated. In device simulation, p-GaN gates were used to achieve E-mode operation in HEMTs. Technology computer-aided design (TCAD) simulation indicated that the saturation drain current (ID, sat) of devices with Schottky and MIS second gates was 88% and 38% lower than that of a single gate structure, while increasing on resistance (Ron) by 31% and 8%, respectively. In device fabrication, a Schottky and MIS second gate were respectively added to an E-mode p-GaN gate HEMT and an E-mode recesses-gate GaN MIS-HEMT. Compared with single-gate structures, the devices with a Schottky and MIS second gates reduced ID, sat by 75% and 32%, respectively, while increasing Ron by 25% and 6%, respectively. The measured electrical characteristics indicate the same trend obtained from TCAD simulation: The dual-gate design can improve the short-circuit capability of GaN HEMTs by reducing the ID, sat under on-state and high-current conditions. [ABSTRACT FROM AUTHOR]

A new Pd|HfO2|AlGaN|GaN metal-oxide-semiconductor (MOS) enhancement-mode high electron mobility transistor (HEMT) is fabricated with low-temperature sensitization, activation, electroless-plating, and two-step gate-recess approaches. Experimentally, a high positive threshold voltage Vth of 1.96 V, a very low gate leakage IG of 6.3 × 10–8 mA/mm, a high maximum extrinsic transconductance gm, max of 75.3 mS/mm, a high maximum drain saturation current ID, max of 266.9 mA/mm, and a high ON/OFF current ratio of 7.6 × 107 are obtained at 300 K. Moreover, the related temperature-dependent characteristics, over temperature ranges from 300 to 500 K, are comprehensively studied. The very low temperature coefficients on gate current, drain saturation current, transconductance, and threshold voltage confirm the thermal-stable capability of the studied device. Therefore, based on these advantages, the studied Pd|HfO2|AlGaN|GaN MOS structure is suitable for the development of high-performance HEMTs. [ABSTRACT FROM AUTHOR]