Capacitance behavior of InAlN Schottky diodes in presence of large concentrations of shallow and deep states related to oxygen

The capacitance-voltage-temperature characteristics of nonintentionally doped In0.16Al0.84 N/n+-GaN Schottky diodes were measured at 1 MHz and in the 90–400 K range. They are discussed in the framework of existing theories, which properly treat the Poisson's equation, especially near the edge of the space-charge region, the so-called transition region. The concentration of a shallow donor and of a deep DX-like center, previously reported, is properly determined. The key parameter to discuss the temperature dependence of the capacitance is the ratio between the frequency of the small ac modulating signal and the temperature-dependent emission rate associated to each level. The capacitance-voltage C-Va curves were successfully fitted using a three parameters expression over the full range of temperatures. The concentration of both shallow and deep levels exceeds a few 1018 cm−3. Based on secondary ion mass spectrometry profiling, we assign both levels to the dominant oxygen impurity. This result supports ou...