Displacement damage effects on the p-GaN HEMT induced by neutrons at Back-n in the China Spallation Neutron Source

Irradiation experiments on p-GaN gate high-electron-mobility transistors (HEMTs) were conducted using neutrons at Back-streaming White Neutron (Back-n) facility at the China Spallation Neutron Source (CSNS). Two groups of devices were float-biased, while one group was ON-biased. Post-irradiation analysis revealed that the electrical performance of the devices exhibited progressive degradation with increasing Back-n fluence, with the ON-biased group demonstrating the most pronounced deterioration. This degradation was primarily characterized by a negative shift in the threshold voltage, a significant increase in reverse gate leakage current, and a slight reduction in forward gate leakage. Further analysis of the gate leakage current and capacitance-voltage characteristics indicated an elevated concentration of two-dimensional electron gas (2DEG), attributed to donor-type defects introduced within the barrier layer by Back-n irradiation. These defects act as hole traps, converting into fixed positive charges that deepen the quantum-well conduction band, thereby enhancing the 2DEG density. Additionally, through the trap-assisted tunneling mechanism, these defects serve as tunneling centers, increasing the probability of electron tunneling and consequently elevating the reverse gate leakage current.