Surface passivation of n-GaN by nitrided-thin-Ga₂O₃/SiO₂ and Si₃N₄ films

The electrical characteristics of n-GaN/nitrided-thin-Ga₂O₃/SiO₂ and n-GaN/Si₃N₄ metal-insulator-semiconductor (MIS) capacitors have been compared, and the work-function difference Φ_ms and effective dielectric-fixed charge density Q_f,eff have been determined. Oxide samples showed lower interface trap level density D_it, lower leakage current, and better reproducibility compared to the nitride samples. The superior properties of the oxide samples are partially attributed to the nitrided-thin-Ga₂O₃ layer (∼0.6-nm-thick). Φ_ms and Q_f,eff were determined, respectively, as 0.13 V and 1.0×10¹² q cm^-2 in oxide and 0.27 V and -3.6×10¹¹ q cm^-2 in nitride samples using flatband voltage versus dielectric thickness data. True dielectric-fixed charge density and location of the major amount of fixed charge are discussed based on Q_f,eff, D_it, and spontaneous polarization of n-GaN.