DEVICE-QUALITY WIDE-GAP HYDROGENATED AMORPHOUS-SILICON FILMS DEPOSITED BY PLASMA CHEMICAL VAPOR-DEPOSITION AT LOW SUBSTRATE TEMPERATURES

Hydrogenated amorphous silicon (alpha-Si:H) films have been fabricated by a plasma chemical vapor deposition (plasma-CVD) method at low substrate temperatures (T(s): 80 or 50-degrees-C) to obtain wide-gap films. Device-quality wide-gap films (photoconductivity under AM-1.5, 100 mW/cm2 illumination approximately 10(-5) OMEGA-1 cm-1, ratio of photoconductivity and dark conductivity approximately 10(6), and Tanc's gap approximately 2 eV) are obtained at low T(s), by optimizing the plasma parameters or by diluting the material gas (SiH4) with H-2. Experimental results suggest that lowering the deposition rate of alpha-SI:H films is an important factor in obtaining high-quality films at low T(s) using a plasma-CVD method.