HYDROGEN REBONDING AND DEFECT FORMATION IN A-SI-H

The effect of short-range hydrogen rebonding in creating metastable defects in a-Si:H is studied with a tight-binding molecular-dynamics model that takes into account both electronic and structural energies. The formation energy of defects created by transferring hydrogen from Si-H sites to weak Si-Si bond sites is found to scale linearly with the Si-Si bond length. This H rebonding mechanism can account for several features of thermally generated and light-induced defects. This suggests that the bond-length disorder may be the dominant factor in controlling the defect density in a-Si:H.