High photoconductivity in dual magnetron sputtered amorphous hydrogenated silicon and germanium alloy films

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Abstract
Thin-film alloys of amorphous hydrogenated silicon and germanium have been grown by dual magnetron sputtering in a chamber with an ultrahigh vacuum base pressure. Photoconductivities greater than 10−7 (Ω cm)−1 with a light flux of 1015 photons/(cm2 s) were obtained for approximately equal concentrations of Si and Ge in near-intrinsic films with optical gaps near 1.4 eV. The intrinsic nature of these films is established by an activation energy of approximately 0.63 eV. Infrared measurements indicate that the maximum photoconductivity is obtained when sufficient hydrogen has been incorporated to result in a small amount of dihydride bonding on both the Si and Ge alloy constitituents.