Transport properties of amorphous InSb and GaAs

Abstract

Electrical conductivity and thermoelectric power of flash evaporated amorphous films of InSb and GaAs are investigated as a function of temperature of boat (evaporation temperature), substrate temperature, deposition at an angle of incidence of vapour beam, and annealing treatment. The properties of the films are very sensitive to the boat temperature; the range of exponential variation of the conductivity with inverse temperature and the corresponding activation energy increase with boat temperature. The thermoelectric power also shows large changes, being relatively temperature independent for films deposited at low boat temperatures and strongly temperature dependent for films deposited at high boat temperatures. The effects of substrate temperature are qualitatively similar to those of evaporation temperature. Annealing of as-deposited films increases the temperature dependence of the conductivity as well as the thermoelectric power. Electron microscopy and diffraction studies suggest that these results are due to occurrence of an excess of group V element in the film. The excess is a function of the evaporation and deposition temperatures.