Capacitance-Voltage Characteristics of AI-2O-3/AIGaN/GaN Structures and State Density Distribution at AI-2O-3/AIGaN Interface

摘要

The potential modulation and interface states of Al-2O-3/Al-0.25Ga-0.75N/GaN structures prepared by atomic layer deposition (ALD) were characterized by capacitance-voltage (C-V) measurements. We observed the peculiar C-V characteristics with two capacitance steps in forward and reverse bias regions, corresponding to the electron accumulation or depletion behavior at the Al-2O-3/AIGaN and AIGaN/GaN interfaces. From the experimental and calculated C-V characteristics, it was found that the charging and discharging of interface states near the AIGaN conduction-band edge mainly caused the stretch-out and hysteresis of the C-V curve at the forward bias. On the other hand, it is likely that the interface states near the midgap or deeper in energies act as fixed charges. From the bias-dependent hysteresis voltage in the forward bias region and the photo-induced voltage shift at the reverse bias, we estimated the interface state density distribution at the AI-2O-3/AIGaN interface for the first time. The present ALD-Al-2O-3/AlGaN/GaN structure showed relatively high interface state densities with a minimum density of 1 × 10~12cm~-2eV~-1 or higher.