Photoconductivity in the amorphous Ge-rich Gex Te1—x system

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Abstract
Experimental results on photoconductivity, Δσ, in as‐deposited and annealed vacuum‐evaporated amorphous films of Gex Te1—x, in the composition range 0.5≤x≤0.7, and of Ge are reported and compared with published photoconductivity data for GeTe2 and Te. Whereas Δσ(T) of Te, GeTe2, and GeTe between 100 and 300°K is characterized by only a single maximum typical of multicomponent chalcogenide glasses, Δσ(T) of the as‐deposited Ge‐rich samples and of as‐deposited and annealed amorphous Ge was found to exhibit a minimum as well as a shallow maximum in this temperature range. A comparison of the present data with those for Te and GeTe2 further shows that amorphous Te is the most sensitive photoconductor in this group of amorphous semiconductors and that the photosensitivity decreases monotonically with increasing Ge content. It is suggested that both the new structure in Δσ(T) and the quenching effect of added Ge are results of increasing densities of localized states—in particular, of midgap states—in compositions with increasing Ge content. Possible correlations between localized‐densities‐of‐states distributions and recombination mechanisms are discussed.