Interaction between arsenic, hydrogen, and silicon matrix in doping of sputtered amorphous hydrogenated silicon

Simultaneous variations of the concentrations of As, Si, and H in As doped and undoped sputtered a-Si:H structures are reported. The As is substitutional for Si, but most of the As atoms are also connected with an additional hydrogen and so inefficient for doping. The As doping also decreases significantly the material density. These results are shown to reject the usual assumption according to which doping atoms just supply carriers in the otherwise unchanged distribution of states of undoped a-Si:H.