Electronic and optical properties of p-type amorphous silicon and wide band-gap amorphous silicon carbide films prepared by photochemical vapor deposition

Abstract

p-type hydrogenated amorphous silicon (a-Si:H) films were prepared by the mercury photosensitized decomposition of a disilane-diborane gas mixture. With increased gaseous impurity ratio (diborane/disilane), the dark conductivity was enhanced. However, the optical band gap was reduced with increasing boron concentration as generally observed in glow discharge produced boron-doped a-Si:H films. Wide optical gap (2.0–2.5 eV) hydrogenated amorphous silicon carbide (a-SiC:H) films were also prepared by the photochemical vapor deposition technique. Acetylene and dimethylsilane were used as the carbon source instead of methane which is usually used in glow discharge system. Moreover, wide optical-gap, p-type a-SiC:H films were photochemically prepared by adding diborane as an impurity to these gas mixtures. A dark conductivity of 3×10−7 (Ω cm)−1 was obtained for p-type a-SiC:H films with an optical band-gap energy of about 2.0 eV.