Oservations were made of light-induced electron capture in O-contaminated (about 5 x 1020/cm3) hydrogenated amorphous Si–Ge alloys grown by hot-wire chemical vapor deposition. By examining the time evolution of dark capacitance after 1.2eV photo-excitation, it was possible to estimate the free energy barrier (greater than 0.8eV) for the release of electrons into the conduction band. Such a large thermal barrier, for a defect whose optical threshold was centered (about 1.35eV) so close to the band-gap (1.5eV), indicates significant configurational relaxation once the O impurity state was occupied with photo-excited electrons.

Junction Capacitance Study of an Oxygen Impurity Defect Exhibiting Configuration Relaxation in Amorphous Silicon–Germanium Alloys Deposited by Hot-Wire CVD. S.Datta, J.D.Cohen, Y.Xu, A.H.Mahan, H.M.Branz: Journal of Non-Crystalline Solids, 2008, 354[19-25], 2126-30