Hydrogenation of polycrystalline silicon thin films

Abstract

Polycrystalline silicon films for solar cells grown by atmospheric pressure chemical vapour deposition require hydrogenation to passivate defects at grain boundaries. Passivation by remote plasma hydrogenation of 12-μm-thick poly-Si films increased Hall effect carrier mobility from 3 to 20 cm 2/Vs, photoluminescence intensity at 0.98 eV band more than 2 times and decreased contrast of local electronic conductivity between grains, observed by combined AFM. However, excessive hydrogenation led to surface damage and defect creation evidenced by widths of Raman LO–TO peak at 520 cm − 1 and X-ray rocking curve of (220) diffraction line. Depth profile by repeated etching of the surface and following the signature of Si–H 2 and H 2 bonding in Raman spectra showed that the damage extended up to 100 nm from the surface.