The lowest-energy defects in tetrahedrally bonded amorphous semiconductors, in particular silane-decomposed films, are analyzed semiquantitatively. The creation energy and effective correlation energy of each defect center are estimated. It is concluded that twofold-coordinated atoms play an important role in these films. The lowest-energy center yielding an EPR signal is not a dangling bond but a positively charged twofold-coordinated atom. The results explain the observed peaks in the density of localized states and the mechanism for the doping of these materials by P and As.

• Received 10 July 1978

DOI:https://doi.org/10.1103/PhysRevLett.41.1755