Role of hydrogen dilution and diborane doping on the growth mechanism of p-type microcrystalline silicon films prepared by photochemical vapor deposition

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Abstract
Boron‐doped microcrystalline hydrogenated silicon (μc‐Si:H) films were grown from a gas mixture of silane, diborane, and hydrogen employing mercury sensitized photochemicalvapor deposition. At a low diborane doping ratio (1.1×10−3) 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 μc‐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.