KINETICS OF LIGHT-INDUCED METASTABLE DEFECT CREATION IN AMORPHOUS-SILICON - A DISPERSIVE EXCITONIC MODEL FOR THE WEAK BOND-DANGLING BOND CONVERSION

The Stutzmann, Jackson, and Tsai model [Phys. Rev. B 32, 23 (1985)] for the creation of metastable defects in illuminated a-Si:H by tail-to-tail recombination of electrons and holes and conversion of weak bonding and antibonding orbitals into dangling bonds has been extended to include the exponential nature of tail states and saturation of dangling bond density. A first-order approximation of the general result gives a stretched exponential formula similar to that of Redfield and Bube [Appl. Phys. Lett. 54, 1037 (1989)] removing an apparent contradiction between the two models. The theroy is also extended to include the thermal annealing process. This gives an apparent saturation of dangling bond density at a steady state equilibrium value N(m) which tends to the actual saturation value N(s) as the intensity of illumination is increased.