High temperature annealing of enhancement-mode AlGaN/GaN high-electron-mobility transistors

The high temperature annealing effect of DC characteristics of the different enhancement-mode AlGaN/GaN high-electron-mobility transistors (HEMTs) were investigated. The threshold voltage shifted from 0.12 V to 0.57 V and the gate leakage current was reduced one order after the recessed-gate enhancement-mode AlGaN/GaN HEMTs were annealed at 500 degrees C for 5 min in N-2 atmosphere. The threshold voltage shifted from 0.23 V to -0.69 V and the gate leakage current increased after the F-implantation enhancement-mode AlGaN/GaN HEMTs were annealed at 400 degrees C for 2 min in N-2 atmosphere. The height of Schottky barrier increased in annealing process that enhanced the depletion of gate to channel electrons, so that the threshold voltage shifted in the positive direction of x axis, the gate leakage current was reduced and the device can work at higher gate voltage. The depletion of F ions and the increased barrier height of F ions were weakened after annealing, so that the threshold voltage shifted in negative direction of x axis and the gate leakage current increased. The channel electron mobility of F-implantation enhancement-mode AlGaN/GaN HEMTs increased obviously after annealing process.