Back-barrier design of N-polar GaN-channel HEMTs with high-resistivity AlGaN buffer on C-face SiC substrate

Abstract We investigated the impact of the aluminum (Al) content in the back barrier (BB) and doping concentration in the compositionally graded aluminum gallium nitride (AlGaN) transition layer on the electrical properties of N-polar high-electron-mobility transistors (HEMTs). A higher Al content in the BB leads to hole accumulation beneath it, which degrades sheet carrier mobility. By introducing appropriate silicon doping into the graded AlGaN layer, hole accumulation can be effectively suppressed. We thus achieved one of the highest reported sheet carrier mobility of 1500 cm 2 V −1 s −1 at a sheet carrier density of 10 13 cm −2 in N-polar GaN-channel HEMTs with an AlGaN BB.