Modelling of Hot Electron Effects in GaN/AlGaN HEMT

Physics-based numerical simulation of an AlGaN/GaN HEMT with additional AlN interlayer (IL) is carried out using both the drift-diffusion (DD) and hydrodynamic (HD) transport models. Assuming that free electrons are supplied by donor-like surface traps (STs) at the top of the AlGaN layer, we show that the AlN IL increases the 2D electron gas density and reduces the ST occupation. The HD model correctly describes ST recharging due to heating of the channel electrons and subsequent thermionic emission into the AlGaN layer. This recharging has a strong effect on channel transport, leading to the creation of a depletion domain, which expands towards the drain with increasing drain bias. The DD model does not include this effect and the depletion region remains unchanged as the drain bias increases.