Properties of a-Si:H films deposited by RF magnetron sputtering at 95°C

In this work we have investigated the dependence of optical and electrical properties of RF sputtered undoped a-Si:H films and B or P doped a-Si:H films on hydrogen flow rate (F-H). Low deposition temperature of 95 degrees C was used, a process compatible with low-cost plastic substrates. FTIR spectroscopy and ESR measurements were used for the investigation of Si-H-x bonding configurations, and concentrations of hydrogen and dangling bonds. We found that there is a strong correlation between the total hydrogen concentration, the dangling bonds density and the optoelectronic properties of the films. The best photosensitivity value was found to be 1.4x10(4) for the undoped films. The dark conductivity (sigma(D)) of the doped layers varied from 5.9x10(-8) to 6.5x10(-6) (Omega cm)(-1) for different ratios F-Ar/F-H. These variations are attributed to both the different B and P concentrations in the films (according to SIMS measurements) and the enhanced disorder of the films introduced by the large number of inactive impurities. The B doping efficiency is lower compared to the P one. A small photovoltaic effect is also observed in n-i-p solar cells fabricated on polyimide (PI) substrates having ITO as antireflective coating, with an efficiency of 1.54%. (C) 2010 Elsevier B.V. All rights reserved.