The effect of the surface fixed charge and donor traps on the C(V) and transfer characteristics of a GaN MISFET — Experiment and TCAD simulations

Fixed charge and surface traps at the passivation/semiconductor interface play a major role in both the on-state and off-state performance as well as reliability of AlGaN/GaN high-voltage transistors. This paper reports a comprehensive analysis of these fixed charges and donor traps using C(V) measurements of a Metal-Insulator-Semiconductor Field-Effect Transistor (MISFET) fabricated alongside a highvoltage HEMT. For the first time, we have correlated the C(V) measurements with the Id-Vg characteristics of the MISFET and have carefully matched them with corresponding TCAD simulations for detailed explanations of the phenomena involved. We have also carried out capacitance measurements at different frequencies and investigated the formation of an inversion layer at the passivation/semiconductor interface and its dependence on the surface charge and donor traps as well as frequency.