Electrical and optical properties of amorphous As₂Te₃ films

We have studied the resistivity, optical absorption and photoconductivity of amorphous As2Te3 films prepared by e-beam evaporation of bulk material on substrates cooled to 77°K. Film thickness were typically several thousand angstroms, and chemical analysis indicated that the films were approximately stoichiometric. The films were stable up to about 450°K above which temperature they tended to devitrify. The resistivity between 200 and 400°K showed an exponential dependence of the resistivity on inverse temperature with an activation energy of 0.4 eV suggesting a "conductivity gap" of 0.8 eV. Optical absorption constants were determined for values of α between 104 and 2 × 105 cm-1 in the energy range from 1.0 to 1.6 eV. Photoconductivity measurements yielded an upper limit of 5 × 10-8 sec for the recombination time and a lower limit of 0.3 cm2/V sec for the mobility of photocarriers. © 1970.