Light-induced metastable defects in amorphous hydrogenated material were suggested to be Si dangling bonds that were associated with pairs of H atoms which broke a Si bond so as to form a complex with two Si-H bonds. This supported the Branz model. These defects were analogous to the H2* defect in crystalline Si, and their energy was related to the bond-angle strain. Several features of the annealing behavior were explained by the existence of this defect complex.

R.Biswas, B.C.Pan: Applied Physics Letters, 1998, 72[3], 371-3