HIGH-QUALITY WIDE-GAP HYDROGENATED AMORPHOUS-SILICON FABRICATED USING HYDROGEN PLASMA POSTTREATMENT

The hydrogen plasma post-treatment of hydrogenated amorphous silicon (a-Si:H) has been investigated to obtain high-quality wide-gap films. The hydrogen plasma treatment after film deposition substantially increases the hydrogen content and the optical gap of a-Si films without deteriorating their optoelectric properties within the range of treatment conditions in this study, where no microcrystallization of the films is observed. A photoconductivity of approximately 10(-5) OMEGA-1 cm-1 and a photosensitivity (the ratio of photoconductivity to dark conductivity) of > 10(6) are obtained for a-Si:H films with an optical gap of > 1.7 eV from the (alphahnu)1/3 plot (> 2.0 eV from Tauc's plot) under AM-1, 100 mW/cm2 illumination. An extremely high open circuit voltage of > 1 V is obtained for an a-Si single-junction cell whose i-layer was fabricated using the hydrogen plasma treatment.