Stable Operation of AlGaN/GaN HEMTs for 25 h at 400C in air

Extreme environments such as the Venus atmosphere are among the emerging applications that demand electronics that can withstand high-temperature oxidizing conditions. While wide-bandgap technologies for integrated electronics have been developed so far, they either suffer from gate oxide and threshold voltage ($V_{th}$ ) degradation over temperature, large power supply requirements, or intrinsic base current. In this letter, AlGaN/GaN high electron mobility transistors (HEMTs) are suggested as an alternative platform for integrated sensors and analog circuits in extreme environments in oxidizing air atmosphere over a wide temperature range from 22C to 400C. An optimal biasing region, with a peak of transconductance ($g_{m,peak}$ ) at 2.3 V with a negligible shift over the temperature range was observed. Moreover, remarkably low $V_{th}$ variation of 0.9 was observed, enabling the design of analog circuits that can operate over the entire temperature range. Finally, the operation of the devices at 400C and 500C over 25 hours was experimentally studied, demonstrating the stability of the DC characteristics after the 5 hours of burn-in, at 400C.