Electrical bias stress related degradation of AlGaN/GaN HEMTs

Effects of electrical bias stress applied for an extended period of time to unpassivated AlGaN/GaN HEMTs have been studied by surface potential and drain current transient measurements. The transient magnitudes were much increased after stress, indicating a larger accumulation of surface charge under the same measurement conditions. In correlation with the increase in transient magnitudes, a permanent reduction in microwave output power of the devices, following stress, was observed.