The H-collision model for light-induced metastability in hydrogenated amorphous samples was described. The recombination of photo-generated carriers was supposed to excite mobile H from Si-H bonds, leaving threefold-coordinated Si dangling-bond defects. When 2 mobile H atoms collided, and associated in a metastable two-H complex, the 2 dangling bonds from which H was emitted also became metastable. This proposed mechanism was consistent with electron spin resonance data. Detailed rate equations for the dangling-bond and mobile-H densities were presented, which included light-induced creation and annealing. The model provided explanations for both the t1/3 time-dependence of the increase in defect density during continuous illumination, and the t1/2 time-dependence during intense laser-pulse illumination.

Hydrogen collision model H.M.Branz: Physical Review B, 1999, 59[8], 5498-512