Electrical and optical properties of amorphous semiconducting GeSe and GeSbSe films

The electrical activation energy and optical band-gap of GeSe and GeSbSe thin films prepared by flash evaporation on to glass substrates have been determined. The conductivities of the films were found to be given by σ = C exp (- E a kT ) , the activation energy E a being 0.53 eV and 0.40 eV for GeSe and GeSbSe respectively. The optical absorption constant α near the absorption edge could be described by α h ̷ ω = k( h ̷ ω−E 0) from which the optical band-gaps E 0 were found to be 1.01 eV for GeSe and 0.67 eV for GeSbSe at 300°K. At 110°K the corresponding values of E 0 were 1.07 eV and 0.735 eV respectively. The significance of these values is discussed in relation to those of other amorphous semiconductors.