Optical and electrical properties of undoped and oxygen-doped a-GeC:H films prepared by magnetron sputtering

Hydrogenated amorphous germanium carbon (a-GeC:H) alloy films have been prepared by magnetron sputtering of germanium in methane–neon gas mixtures. The dependence of structural, optical and electrical properties on the methane partial pressure (Rm) has been investigated. With increasing Rm, the concentration of hydrogen bonded to germanium and carbon, the optical band gap Eo, and the activation energy Ed of dark conductivity σd increase, while the Urbach energy Eu and σd decrease. On the basis of these results, we have made an attempt to add oxygen to a-GeC:H by introducing oxygen during deposition. It is found that σd shows a maximum and Ed shows a minimum as a function of the oxygen partial pressure, while Eo and Eu tend to increase slightly.