COMPARISON BETWEEN ELECTRICAL-PROPERTIES AND ELECTRONIC-STRUCTURE OF VARIOUSLY-PREPARED GERMANIUM SELENIDE FILMS

Electronic structure and properties have been compared for amorphous g ermanium selenide films with compositions near GeSe2 to GeSe3, and pre pared by either plasma-enhanced chemical vapour deposition (PECVD) of GeH4 and H2Se mixtures, or by thermal evaporation of bulk germanium se lenide compounds. X-ray photoelectron spectroscopy (XPS) is used in co njunction with photo- and dark conductivity measurements. XPS spectra from Ge 3d and Se 3d core levels, and of the valence band, reveal no s ignificant difference in electronic structure, but the electrical meas urements point to a different position of the Fermi level in the two t ypes of material. It is suggested that PECVD produces a distribution o f localized gap states which pushes the Fermi level closer to the tran sport band.