Electrical Properties of Amorphous InSb

Amorphous InSb films were prepared by getter sputtering on substrates held at 77^∘{}K and at room temperature. The films prepared at 300^∘{}K are very similar to films evaporated at lower temperatures: Their resistivity increases exponentially with decreasing temperature (intrinsic conduction) with an electrical band gap Egᵉˡ of about 0.5 eV. On the other hand, films deposited and kept at 77^∘{}K have a temperature-dependent resistivity which is well fitted between 10 and 120^∘{}K by the relation ρ=ρ₀exp[(T₀T)(1/4)], with T₀2×10⁷^∘{}K, thus suggesting that conduction in such films takes place via a thermally activated hopping mechanism. Above 120^∘{}K the films anneal as shown by the increasing resistivity with increasing temperature; after annealing the films display again an exponentially temperature-dependent resistivity similar to that of a room-temperature-deposited film. InSb is therefore an interesting amorphous semiconductor from the point of view that either intrinsic or hopping conduction over most of the accessible temperature range can be achieved by varying the conditions of deposition; this suggests that the localized states between which electrons are hopping in the films deposited at 77^∘{}K may be linked with the greater degree of disorder present in such films.