The Influence of Charge Trapping Effects on GIT GaN-Based HEMTs

In this work, we investigate the degradation behavior of gate injection transistor (GIT) GaN-based high-electron-mobility transistors (HEMTs) under gate overdrive stress and the evolution of the deep traps by using capacitance mode deep-level transient spectroscopy (C-DLTS). With increasing the aging time, a negative shift of the threshold voltage (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}$</tex-math> </inline-formula>) was observed with increased gate leakage current. Before the stress, three trap signals were detected in GaN-based HEMTs, including one electron trap (at 150 K) and two hole traps (at 250 and 450 K). After the stress, two electron traps appeared at 90 and 350 K, while for intrinsic hole traps at 250 K, there was no obvious change after the stress. The DLTS peak intensity of the hole trap located at 450 K has a logarithmic dependence on the filling pulse width, indicating it is related to the dislocations. Furthermore, HRTEM results show that threading dislocations (TDs) pass through the p-GaN/AlGaN/GaN after the stress, which may facilitate the new interfacial state electron trap at 350 K. The dominant mechanism for the leakage currents changed from Poole–Frenkel (PF) emission to trap-assisted tunneling (TAT) after the stress. This study helps to further understand the charge trapping effect in the GaN-based HEMTs.