Current instability in power HEMTs

We present an experimental and theoretical study of current instability in an Al0.23Ga0.77As/In0.23Ga77As n-channel delta-doped pseudomorphic high electron-mobility transistor (HEMT). Monte Carlo simulations of the device Indicated that it was vulnerable to the formation of unusual 'transverse' Gunn dipoles which caused sudden reductions in the drain current. These dipoles were also responsible for a significant number of impact ionization events at higher drain potentials causing a subsequent upturn in the drain current, Our experimental observations of a similar device are in excellent qualitative and good quantitative agreement with our theoretical predictions and so provide compelling evidence for the existence of Gunn instabilities in HEMTs.