Measured and calculated distributions of deep defect states in hydrogenated amorphous silicon: Verification of deep defect relaxation dynamics

The density of states in the upper half of the mobility gap of both intrinsic and n-type a-Si:H samples was determined by the modulated photocurrent (MPC) and junction capacitance methods. We conclude that the narrow defect band revealed by the MPC measurements reflects the distribution of relaxed D⁰ states, while the broader and deeper defect band obtained by capacitance measurements corresponds to relaxed D^- states. Both distributions are correctly predicted by a calculation that takes into account the relaxation dynamics of deep defects in these different charge states.