Capacitance techniques for the evaluation of electronic properties and defects in disordered thin film semiconductors

The theoretical background of the Schottky barrier capacitance of disordered semiconductors is recalled and the temperature, frequency, and bias dependence of the capacitance is illustrated on hydrogenated amorphous silicon (a-Si:H), hydrogenated polymorphous silicon (pm-Si:H) and hydrogenated microcrystalline silicon (μc-Si:H). Both a-Si:H and pm-Si:H follow the same trends, with a lower defect density in pm-Si:H. Quite different features are observed in μc-Si:H, and are related to different defect levels and to the two-phase constitution of the material. Finally, the capacitance analysis is reviewed in the framework of the amphoteric dangling bond states, where the influence of both defect transitions is emphasized.