Electrical contact properties of semiconducting chalcogenide glasses

Measurements of the d.c. conductivity of radio-frequency sputtered thin films of a Ge-As-Te chalcogenide glass, sandwiched between a variety of metallic electrodes, indicate the absence of any blocking barrier associated with the metal-amorphous semiconductor contact, except when an oxidizing electrode such as Al is used. These results are confirmed by measurements of the capacitance and a.c. conductance as a function of frequency and are analysed in terms of a model of the metal-amorphous semiconductor contact in which transport occurs by a parallel combination of thermionic field emission, band-to-band recombination/ generation via localized gap states, and tunnelling at the Fermi level followed by thermal excitation into the conduction band. Calculations show that recombination/generation is the dominant mechanism of transport across the contact.