Device-quality wide-gap hydrogenated amorphous silicon films deposited by plasma chemical vapor deposition at low substrate temperatures.

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Abstract
Hydrogenated amorphous silicon (a‐Si:H) films have been fabricated by a plasma chemical vapor deposition (plasma‐CVD) method at low substrate temperatures (Ts : 80 or 50 °C) to obtain wide‐gap films. Device‐quality wide‐gap films (photoconductivity under AM‐1.5, 100 mW/cm2 illumination ∼10−5 Ω−1 cm−1, ratio of photoconductivity and dark conductivity ∼106, and Tanc’s gap ∼2 eV) are obtained at low Ts, by optimizing the plasma parameters or by diluting the material gas (SiH4) with H2. Experimental results suggest that lowering the deposition rate of a‐Si:H films is an important factor in obtaining high‐quality films at low Ts using a plasma‐CVD method.