Crossover from Nearest-Neighbor Hopping Conduction to Efros-Shklovskii Variable-Range Hopping Conduction in Hydrogenated Amorphous Silicon Films

Abstract

We presented the results of optical and electrical studies of the properties of hydrogenated amorphous silicon (a-Si H) film which was prepared by hot wire method. Using transmittance measurements, the dielectric constant of the a-Si H was determined. The temperature-dependent conductivity was measured using the two-point probe method in the temperature range 115-326 K. It was shown that the temperature-dependent conductivity can be well explained by the nearest-neighbor hopping conduction and the Efros-Shklovskii variable-range hopping conduction models A clear transition from the nearest-neighbor hopping conduction mechanism to the Efros-Shklovskii variable-range hopping conduction mechanism was also observed The transition between two conduction regimes and characteristic hopping temperatures, as well as the complete set of parameters describing the properties of the localized electrons (the localization length, the hopping energy, the hopping distance, the width of the Coulomb gap, and the value of the density of states at the Fermi level) were determined (C) 2009 The Japan Society of Applied Physics