Defect creation and removal in hydrogenated amorphous silicon predicted by the defect-pool model and revealed by the quasistatic capacitance of metal-insulator-semiconductor structures

The quasistatic capacitance of metal-insulator-semiconductor structures is shown to be a powerful tool to study the defect formation in hydrogenated amorphous silicon (a-Si:H), and it is used to test the defect-pool model. Numerical calculations demonstrate that, in the framework of this model, the changes in the density of dangling bond stares induced by thermal bias annealing are reflected in the shape of the capacitance Versus the gate bias (C-V) curve. Though some details of experimental C-V curves obtained on aluminum/silicon dioxide/a-Si:H structures are not explained by this model, the major model characteristics are clearly observed. In particular, it is confirmed that a bump of dangling bond states is created below or above midgap, depending on whether the Fermi level is moved towards the conduction or the valence band during thermal bias annealing.