Investigation of Electrical Characteristics and Trapping Effects in p-GaN Gate HEMTs Under Electron Irradiation

In this work, the variations of the electrical properties and trapping effects of p-GaN gate high-electron-mobility transistors (HEMTs) under 1-MeV electron irradiation were investigated systematically. When the irradiation fluence was increased, the drain-source current and the gate leakage current also uprose, but the threshold voltage shifted toward the negative direction. Specifically, after final irradiation, traps in these devices were identified via the current-transient method, and alteration of the trapping effects near the drain and gate could be observed, respectively, by applying different filling voltages. According to the time constant spectra (TCS) and differential amplitude spectra (DAS), six types of detrapping behaviors could be identified. When compared with the results during the pristine stage, the absolute amplitudes of the traps changed after irradiation, which indicated trap densities decreased near the drain and those increased near the gate. The observed changes in the trapping behaviors are consistent with the changes in the electrical properties. To identify the activation energies and locations of traps, the current-transient response was measured at various temperatures before and after electron irradiation. The possible reason for the increased activation energies is that electron irradiation turned the Ga vacancies that decorated the dislocations into pure dislocations and increased the barrier height.