Electrical characterization of amorphous germanium dioxide films

Amorphous germanium dioxide (GeO2) films have been deposited by electron beam evaporation onto different substrates including glass, SnO2 conducting glass, evaporated gold and n-type silicon in order to examine the electrical behaviour of GeO2 in metal/insulator/metal (MIM) and metal/insulator/semiconductor (MIS) structures. In MIM structures the as-deposited films are strongly influenced by electrode barriers but heat treatment at 600 K induced ohmic behaviour. The dielectric response of the films in the frequency range 0.1-100 kHz and the temperature range 180-350 K showed that the dielectric constant at 300 K was 9 and was virtually independent of frequency, while the a.c. conductivity follows the relation σ ∞ ω s, where s is temperature dependent. Good agreement with a classical electronic hopping model is obtained. In MIS structures, GeO2 on silicon gives rise to heterojunction behaviour at low voltages while, at higher voltages, the d.c. conduction is bulk dominated and exhibits space-charge-limited conduction. The dielectric response of MIS structures is strongly influenced by the depletion capacitance at the interface between GeO2 and silicon