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.