Structural, optical and electrical properties of helium diluted a-Si1−C :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. (c) 2006 Elsevier B.V. All rights reserved.