Subthreshold and turn-on characteristics in Schottky-type p-GaN Gate HEMTs: impact of partially and fully depleted p-GaN layer

In this work, the impact of partially depleted and fully depleted p-GaN (PDP-GaN and FDP-GaN) layers on the gate characteristics of Schottky-type p-GaN Gate HEMTs is investigated. Four wafers are fabricated via different annealing temperatures to achieve the PDP-GaN and FDP-GaN layers. Devices with PDP-GaN show nearly identical SS/VTH, while Gm,max enhances with increased activated Mg concentration. Meanwhile, the device with FDP-GaN demonstrates higher SS, lower VTH, and specific Gm,max compared to the others. It turns out that subthreshold and turn-on characteristics are attributed to the position of the Fermi level in p-GaN and the Schottky tunneling leakage current, respectively.