Capacitance-voltage characterization of GaAs–Al2O3 interfaces

The authors apply the conductance method at 25 and 150°C to GaAs–Al2O3 metal-oxide-semiconductor devices in order to derive the interface state distribution (Dit) as a function of energy in the bandgap. The Dit is governed by two large interface state peaks at midgap energies, in agreement with the unified defect model. S-passivation and forming gas annealing reduce the Dit in large parts of the bandgap, mainly close to the valence band, reducing noticeably the room temperature frequency dispersion. However the midgap interface state peaks are not affected by these treatments, such that Fermi level pinning at midgap energies remains.