Projects

Study of hot wire chemical vapour deposited a-si:H and its alloys

The primary goal of my Ph.D. project was to explore the potential of the Hot Wire CVD process for the deposition of various a-Si:H based alloy thin films. Thus the work consists of deposition, characterization and integration of the different individual layers of a-Si:H based thin films such as a-Si:H, mc-Si:H, poly-Si, a-SiN:H and a-SiC:H in Solar cells, MOS capacitors and Thin Film Light Emitting Diodes. Gas phase chemistry analysis during the deposition process to deduce a correlation between gas phase chemistry and film properties, is another important aspect of this work. By using low H2 dilution of SiH4, a-Si:H films with H content less than 5 at % and photoconductivity gain ~106 have been deposited. More than 90 % recovery in photoconductivity is observed after annealing of the degraded a-SiH films. Doped p-type and n-type mc-Si:H films (thickness ~ 4000 u with highest ever conductivity of 107 (W-cm)-1 and 226(W-cm)-1 respectively have been achieved. Grain size of these films increases from ~ 2 nm to ~ 11 nm with increase in substrate temperature from 150oC to 350oC. More Info

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