INFLUENCE OF SILICON ON THE PROPERTIES OF REACTIVELY SPUTTERED HYDROGENATED AMORPHOUS-GERMANIUM

Hydrogenated amorphous germanium-silicon films (a-Ge1-xSix:H, 10(-3)<x<10(-1)) were prepared by reactive dc-magnetron sputtering from a germanium target in an Ar/H-2/SiH4 atmosphere. Silicon incorporation leads to a decrease of the dark conductivity sigma(D) (mainly independent of the hydrogen pressure) and a weaker decrease of the photoconductivity sigma(ph) (strongly dependent on the hydrogen pressure) and has no influence on the gap state density detected by photothermal deflection spectroscopy. The best photoconductivity corresponding to mu-tau = 10(-5) cm2/V was obtained under the highest hydrogen pressure and is not influenced by silicon up to x=0.01. The ratio of sigma(ph)/sigma(D) under monochromatic excitation (632 nm, 9 mW/cm2) increases from 0.25 in a-Ge:H to more than 1 in a-Ge0.99Si0.01:H.