Temperature dependence of the threshold voltage of AlGaN/GaN/SiC high electron mobility transistors
Shifts in the threshold voltage V T subject to temperature in AlGaN/GaN-based high-electron-mobility transistors (HEMTs) grown on silicon carbide substrate are reported. Variation of V T with drain–source voltage and temperature is investigated, including experimental characterization, modelling and analysis. Possible parameters that affect V T are Schottky barrier height of the device, along with trap-assisted phenomena, aluminium concentration and polarization fields depending on the dielectric, were studied. The threshold voltage and Schottky barrier height shift positively with temperature, and a zero temperature coefficient point in the transfer curve was found before the threshold voltage. An analytical model for threshold voltage V T based on lattice-mismatched Al x Ga1−x N/GaN HEMTs is presented based on aluminium mole concentration, and it is found that V T shifts towards more negative values with increasing aluminium concentration. The model correctly predicts device performance and is found to be consistent with the measured results. These results are valuable for understanding the underlying physics of GaN/SiC HEMTs and their optimization with temperature.