TRANSPORT NEAR THE MOBILITY EDGE, THE SIGN OF THE HALL-EFFECT, PHOTOREDUCTION AND OXIDATION OF AMORPHOUS INO-CHI

The electronic transport properties of amorphous indium oxide (a-InOx) are studied as samples are changed reversibly between semiconducting and metallic states by photoreduction and reoxidation. Photons with hv greater than or equal to 3.5eV produce conducting states in which holes are self-trapped presumably in weak O-O bonds. Screening induces a nonmetal-metal transition at high electron concentrations n, while at lower n the temperature dependence of the conductivity follows the Meyer-Neldel rule with parameters nearly identical to hydrogenated amorphous silicon. The normal sign and magnitude of the Hall effect may be due to the strongly ionic character of the bonding.