Electrical Characteristics of GaN and Si Based Metal-Oxide-Semiconductor (MOS) Capacitors

Abstract

We report on the electrical properties of Al2O3 and TiO2 dielectrics in three different MOS capacitors of Al2O3/n-Si, TiO2/n-Si, and Al2O3/n-GaN. Hysteresis analysis of capacitance-voltage data and shifts in flat band voltages showed that the interface electrical quality of TiO2/Si was superior compared to that of Al2O3/Si and Al2O3/GaN. The growth temperature during atomic layer deposition were varied and Al2O3 deposited at 300°C on GaN and TiO2 deposited at 200°C on Si had better electrical property. The dielectric constant of the unannealed TiO2 was low and only the brookite crystalline phase of TiO2 was detected by XRD. The variation in the capacitance on some MOS capacitors was related to nonuniformities of the TiO2 oxide surface, as found from AFM images. The leakage current densities were low, as obtained from current-voltage measurement of Al2O3 and TiO2 gate oxide.