A.C. and D.C. electrical conductivity in amorphous arsenic trisulphide films

Abstract

Abstract It is shown that measurements of a.c. and d.c. conductivity in undoped amorphous As2S3 films differ in several respects from those reported in other chalcogenide glasses. Experiments show conclusively that the a.c. lows in this material are due to a bulk-controlled process. The frequency-dependent but temperature-independent a.c. conductivity curves have been interpreted in terms of a thermally assisted hopping mechanism in which correlation effects are important. The carrier concentration deduced from these data is in agreement with the number of free spins obtained from magnetic susceptibility measurements. Two types of d.c. current-voltage characteristics are reported: (a) ohmic curves, interpreted in terms of extrinsic conduction, which vary linearly with the inverse of thickness and have an activation energy substantially less than one half the energy for the occurrence of strong interband optical absorption in As2S3; (b) nonohmic curves, interpreted in terms of recombinative space charge injection, which contain a region where the current varies approximately with the square root of voltage and whose activation energies are electric field-dependent.