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

摘要

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 (Fh). Low deposition temperature of 95℃ 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 1.4×10~4 for the undoped films. The dark conductivity (σ_D) of the doped layers varied from 5.9×10~(-8) to 6.5×10~(-6) (Ω cm)~(-1) for different ratios F_(Ar_/FH. 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%.