High Temperature RF Characterisation of SiN Passivated and Unpassivated AlGaN/GaN HFETs

Abstract

AlGaN/GaN heterojunction field effect transistors were tested at elevated temperatures, up to +180°C, to determine the effect on the device performance. Ageing of the device during these measurements was also studied. A comparison between devices fabricated with and without silicon nitride surface passivation was made. For devices with surface passivation, both f T and f max reduce with increasing temperature. This is different from the behaviour of the devices without surface passivation. In these devices, there is an initial increase in both f T and f max . Above 70°C, any further increase in temperature causes a reduction in both f T and f max . When devices are allowed to cool to room temperature and are subsequently re-measured, they show an increase in f T and f max from the values initially recorded; thus indicating some form of device anneal.