Substrate Bias Stress Induced Kink Effect in GaN-on-Silicon High-Electron-Mobility Transistor

In this paper, kink effect observed in the output characteristics of the AlInN/GaN-on-Si high electron mobility transistor (HEMT) after subjecting the Si-substrate to positive/negative bias stress has been studied. The charge distribution in the different buffer layers of the wafer in the presence of different substrate-bias stress has been discussed in detail. It is concluded that the induced kink is due to the trapping/de-trapping of charge carriers through acceptor-like deep levels present in the GaN buffer layer. TCAD simulations have been performed to understand the electric-field distribution within the device layers, which is strongly related to the observed kink phenomenon. Two types of traps, acceptor-like (Ea1 = 0.52 eV) and donor-like (Ea2 = 0.44 eV), were extracted from temperature-dependent drain current transient analysis using back-gating experiment. It is concluded that a carbon-induced deep acceptor-like trap is responsible for the observed kink effect.