Charge control and mobility studies for an AlGaN/GaN high electron mobility transistor

A charge control model and a mobility model are developed for the Al–GaN/GaN high electron mobility transistor (HEMT) device. The model addresses issues of how piezoelectric effect and interface roughness influence device properties. We find that even small amount of interface roughness has very strong effect on the two-dimensional electron gas properties. Low-lying electronic states are strongly localized and transport through these states is not described by Born approximation but by phonon-assisted hopping. At low temperature the effects of localization are quite important and we use the Kubo formula to study this transport. Results for charge control and mobility are presented as a function of Al composition in the AlGaN/GaN HEMT.