Monte Carlo simulations of AlGaN/GaN heterojunction field-effect transistors (HFETs)

Self-consistent Monte Carlo simulations are reported for AlGaN/GaN HFETs. Hot-carrier scattering rates are determined by fitting experimental ionization coefficients and the doping character of the GaN is obtained from substrate bias measurements. Preliminary simulations for a simple model of the AlGaN surface are described and results are found to be consistent with experimental data. The high-frequency response of short-gate-length transistors is found to be sensitive to the charge state of the free AlGaN surface and it is proposed that current-slump phenomena may also be related to deep levels at this surface. Breakdown calculations show interesting two-dimensional effects close to the drain contact.