Dependence of RF performance of GaN/AlGaN HEMTs upon AlGaN barrier layer variation

The dependence of microwave performance of GaN/AlGaN high electron mobility transistors (HEMTs), namely the unity gain current cut-off frequency (f_T) and the maximum oscillation frequency (f_MAX), are reported as a function of the mole fraction of Al and the thickness of the barrier AlGaN layer. The parameters are computed using a physics-based model and compared to experimental results. Schrodinger and Poisson´s equations are solved self-consistently to relate the applied gate bias to the channel electron concentration. The contributions of both spontaneous and piezoelectric polarizations towards f_T are explored. Finally, because of interest in using this family of devices at elevated temperatures, each simulation was repeated between 300K and 500K for comparison.