Role of Deposition Pressure on Properties of Phosphorus Doped Hydrogenated Nano-Crystalline Silicon (nc-Si:H) Thin Films Prepared by the Cat-CVD Method

Objective: Phosphorus doped hydrogenated nano-crystalline silicon (nc-Si:H) thin films were synthesized by catalytic chemical vapor deposition (Cat-CVD) method. Methods: The effect of deposition pressure on opto-electronic and structural properties was studied using various analysis techniques such as low angle XRD analysis, FTIR spectroscopy, Raman spectroscopy, UV-Visible spectroscopy, dark conductivity, etc. Results: From low angle XRD and Raman spectroscopy analysis, it is observed that an increase in deposition pressure causes Si:H films to transform and transit from amorphous to the crystalline phase. At optimized deposition pressure (300 mTorr), phosphorous doped nc- Si:H films having a crystallite size of ~29 nm and crystalline volume fraction of ~58% along with high deposition rate (~29.7 Å/s) have been obtained. The band gap was found to be ~1.98 eV and hydrogen content was as low as (~1.72 at.%) for these films. Conclusion: The deposited films can be useful as an n-type layer for Si:H based p-i-n, tandem and c-Si hetero-junction solar cells.