Passivation of hole traps in SiO₂/GaN metal-oxide-semiconductor devices by high-density magnesium doping

A major challenge in GaN-based metal-oxide-semiconductor (MOS) devices is significant hole trapping near the oxide/GaN interface. In this study, we show that the density and energy level of the hole traps depends crucially on the concentration of magnesium (Mg) dopants in GaN layers. Although the surface potential of a conventional SiO2/p-GaN MOS device is severely pinned by hole trapping, hole accumulation and very low interface state densities below 10(11) cm(-2) eV(-1) are demonstrated for MOS capacitors on heavily Mg-doped GaN epilayers regardless of the degree of dopant activation. These findings indicate the decisive role of Mg atoms in defect passivation.