EFFECT OF DEPOSITION PARAMETERS ON THE PROPERTIES OF AMORPHOUS-SILICON GERMANIUM ALLOY-FILMS GROWN BY THE PHOTO-CVD METHOD

A significant improvement in structural, optical and electrical proper ties of a-SiGe:H films grown by the photochemical vapour deposition me thod has been achieved through a selection of chamber pressure, substr ate temperature and hydrogen dilution. By varying these process parame ters, a-SiGe:H films having dominant silicon and germanium monohydride bonds were produced (from IR analysis) which have less microstructure related disorder, sharp valence band tail width (E0) and low dangling -bond density (N(s)). As a consequence the magnitude of the photogener ated carrier (generation efficiency-mobility-lifetime product, etamuta u) improved by two orders of magnitude. This resulted in a photoconduc tivity (sigma(Ph)) of 10(-5) S cm-1 along with a dark conductivity (si gma(D)) of 10(-10) S cm-1 for a-SiG:H film having a band gap of 1.5 eV .