Inadequacy of the Mott–Schottky equation in strongly pinned double Schottky barriers with no deep donors

The capacitive behaviour of an intergranular double Schottky barrier in a polycrystalline semiconductor was evaluated. We found that the widely applied version of the Mott–Schottky equation can lead to significant errors. Even though we considered strong Fermi level pinning at the interface and no deep levels, the Mott–Schottky equation can be inadequate leading to huge errors due to voltage splitting at double Schottky barriers. Experiments carried out on ZnO varistors corroborated the main trends of our analysis.