HYDROGENATED AMORPHOUS-SILICON SULFUR ALLOY DEPOSITED WITH HYDROGEN DILUTION

Device quality hydrogenated amorphous silicon sulfur alloy films were prepared by plasma-enhanced chemical vapor deposition with hydrogen dilution. The optical absorption, elemental composition, photoresponse and density of defect states of the alloy films were investigated. The alloy exhibited a wider optical bandgap with increasing sulfur concentration in the films. The photo-conductivity of the alloy film was about 10(-4) S/cm, and of the same order of magnitude as for amorphous silicon. The light to dark conductivity ratio of the sulfur alloy film deposited with hydrogen dilution is approximately 10(4), higher than that of film prepared without hydrogen dilution. The presence of hydrogen in the rf discharge plasma may sputter off the weakly bonded clusters on the growing surface, lead to a dense network, and consequently improve the film quality.