Photocarrier dynamics in compensated hydrogenated amorphous silicon

The photocarrier dynamics in compensated a-Si:H is studied using the time-dependent photomodulation technique in the subpicosecond-to-millisecond time range. We find that photocarriers are quickly trapped in shallow impurity levels for t < 10 psec, similar to the behavior in singly doped materials. However, their recombination kinetics for t > 10 nsec and their steady-state properties are not substantially different from those in undoped materials. This behavior is explained by fast trapping in donor and acceptor states and thermalization into deeper band-tail states which are similar to those in undoped materials.