The hydrogen collision model: theory and experiment

The H collision model of the Staebler-Wronski effect in hydrogenated amorph ous silicon attributes light- and carrier-induced metastability to the asso ciation in pairs of mobile H that have diffused long distances after excita tion from Si-H bonds. This microscopic model is consistent with the constra ints imposed by electron spin resonance and other experiments. Mobile H den sity is the key variable of the quantitative theory describing metastable d angling-bond creation. As predicted, pulsed illumination experiments show t hat there is an intermediate precursor between electron-hole recombination and metastable dangling-bond (DB) creation. I suggest this precursor is mob ile H: whose density normally requires about a millisecond to respond to ch anges in illumination. The numerical constants describing H emission and tr apping within the H collision model are estimated from recent pulsed-illumi nation experiments. A representative numerical solution of the model is sho wn. (C) 2000 Elsevier Science B.V. All rights reserved.