DEFECT CREATION AND REMOVAL IN HYDROGENATED AMORPHOUS-SILICON PREDICTED BY THE DEFECT-POOL MODEL AND REVEALED BY THE QUASI-STATIC CAPACITANCE OF METAL-INSULATOR-SEMICONDUCTOR STRUCTURES

The quasistatic capacitance of metal-insulator-semiconductor structure s is shown to be a powerful tool to study the defect formation in hydr ogenated 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 ind uced by thermal bias annealing are reflected in the shape of the capac itance Versus the gate bias (C-V) curve. Though some details of experi mental C-V curves obtained on aluminum/silicon dioxide/a-Si:H structur es are not explained by this model, the major model characteristics ar e clearly observed. In particular, it is confirmed that a bump of dang ling bond states is created below or above midgap, depending on whethe r the Fermi level is moved towards the conduction or the valence band during thermal bias annealing.