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

Abstract

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 depend crucially on the concentration of magnesium (Mg) dopants in GaN layers. Although the surface potential of a conventional SiO2/p-GaN MOS devices is severely pinned by hole trapping, hole accumulation and very low interface state densities below 1011 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.

Separate evaluation of interface and oxide hole traps in SiO2/GaN MOS structures with below- and above-gap light excitation

“…These hole traps could impair the switching performance and threshold voltage stability of MOS devices and thus have to be eliminated. While low hole trap density has recently been demonstrated for SiO 2 /GaN samples with very high magnesium doping concentration (10 18 -10 19 cm −3 ), 22,23) the mechanism of defect passivation remains unclear. To gain better control over the hole traps in SiO 2 /GaN structures, having insight into their origin is crucial.…”