Safe hole traps—a source of metastable light-induced dangling bonds in a-Si:H

Abstract

We apply a newly developed technique to determine ‘safe hole trap’ distributions in a-Si:H from secondary photocurrent transients. Because of changes of the safe hole trap distributions caused by light-soaking and subsequent anneals, we suggest that hole traps located 0·4–0·5 eV above the valence-band edge are the source of metastable dangling bonds induced by light-soaking at room temperature. At 163 K, four times as many safe hole traps are lost as for the light-soaking at room temperature. During annealing experiments, recovery of safe hole traps converted at 163 K is much faster than the recovery of safe hole traps converted at room temperature. We conclude that the exact configuration for lattice-relaxed metastable defects originating from safe hole traps depends on the temperature at which they are formed.