Structural, optical and electrical properties of helium diluted a-Si1−xCx:H films deposited by PECVD

We present results on optical, structural and electrical properties of a-Si1−xCx:H films deposited by plasma enhanced chemical vapor deposition in the low power regime, with C fraction from 0 to 0.28. The absorption coefficient has been obtained in the region 0.73–4.5 eV by means of ellipsometry, reflectance–transmittance and photothermal deflection spectroscopy. The addition of carbon in the alloy increases the disorder and the density of defects: samples deposited with high carbon content have poorer optoelectronic properties. Two conduction regimes are observed: extended state conduction and hopping conduction in the conduction band tail. A visible PL peak that widens and shifts to higher energies as the carbon content increases has been observed.