Transport and localized levels in amorphous binary chalcogenides

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Abstract
Measurements of photoconductivity versus intensity and temperature, photoconductivity decay, thermoelectric power versus temperature, and field effect have been extended to several binary amorphous semiconductors: Sb2Te3, As2Te3, As2Se3, and Ge2Te7, to be compared with earlier measurements on As2SeTe2 and Ge3Se2Te4 and more complex multicomponent chalcogenides. Analogous behavior is found in all these materials: about 1019 cm−3 eV−1 localized recombination levels within about 0.1 eV of the gap edges; about 1019 cm−3 eV−1 localized levels near the equilibrium Fermi level; thermally activated mobility with activation energy of the order of 0.1–0.2 eV. Crystallization produces an increase in photoconductivity at 100°K by over a factor of 106.