ROLE OF HYDROGEN DILUTION AND DIBORANE DOPING ON THE GROWTH-MECHANISM OF P-TYPE MICROCRYSTALLINE SILICON FILMS PREPARED BY PHOTOCHEMICAL VAPOR-DEPOSITION

Boron-doped microcrystalline hydrogenated silicon (mu-c-Si:H) films were grown from a gas mixture of silane, diborane, and hydrogen employing mercury sensitized photochemcial vapor deposition. At a low diborane doping ratio (1.1 x 10(-3)) hydrogen dilution of source gases resulted in films exhibiting a maximum conductivity of 7.4 S cm-1. For a higher doping ratio (10(-2)) the value of conductivity remained almost unchanged (10(-5)-10(-6) S cm-1) with hydrogen dilution indicating nonexistence of microcrystallinity under such conditions. Transmission electron microscopy of B-doped mu-c-Si:H films revealed formation of crystallites possessing different crystallographic orientations, e.g., (111), (220), and (311) along with other planes. X-ray spectra confirmed a large number of crystallites with (220) orientations.