ENERGY-LEVEL DYNAMICS OF DEEP GAP STATES IN HYDROGENATED AMORPHOUS-SILICON UNDER ILLUMINATION

Relaxation dynamics of deep defects, recently observed in modulated ph otocurrent and electron drift measurements, are explained in terms of random temporal fluctuations of localized-state energies. The fluctuat ions can be caused by a randomly changing microscopic configuration of excess charge carriers or by carrier annihilation processes. A model is developed which leads to dependences of the thermal emission energy upon temperature and optical bias, in good agreement with existing ex perimental data.