Charge redistribution among defects in heavily damaged silicon

We have studied trapping kinetics of defects during carrier capture in heavily damaged silicon, where damage was induced by MeV heavy ions at doses near but below the amorphization threshold. Using spectroscopic junction transient measurements, we provide unambiguous evidence of charge redistribution between defects. These results imply that changes in the occupancy of gap states are responsible for the deepening of emission energies with filling time, as is commonly observed in transient experiments in disordered silicon. This is in contrast to its usual explanation in terms of deepening of energy states due to hierarchical defect relaxation.