Abstract
Electrical trap states in the AlGaN-based high-electron-mobility transistor (HEMT) structures limit the performances of devices. In this study, we present a comprehensive study of the electrical trap states in AlGaN/GaN HEMT structures and examine their influence on the device performance. We performed capacitance-frequency and conductance-frequency measurements to determine the time constant and the density of the interface states. The density of the interface states was calculated to be 2 X 10(10) cm(-2) eV(-1), and the time constant of the interface states was 1 mu s. Deep-level transient spectroscopy showed the presence of one electron trap E1 (negative peak) and three hole-like traps P1, P2, and P3 (positive peaks). The thermal activation energies for E1, P1, P2, and P3 traps were calculated to be 1.19, 0.64, 0.95, and 1.32 eV, respectively. The electron trap E1 and the hole-like traps P1, P2 and P3 were observed to originate from the point defects or their complexes in the material. The hole-like traps reflected the changes created in the population of the surface states owing to the capture of the surface states; these traps originated from the point defects related to the nitrogen vacancy.