TEMPERATURE AND ELECTRIC FIELD DEPENDENCE OF HOPPING CONDUCTION IN A TWO DIMENSIONAL IMPURITY BAND.

Abstract

For electric fields in which the current-field characteristic is ohmic (F congruent 0. 4 v/cm), the dc conductivity associated with a sodium impurity band in a silicon MOSFET has been found experimentally to be consistent with a given formula. The correspondence between the observations on sodium impurity bands and the predictions of the theory for a two dimensional random system indicates that the low temperature ohmic conductivity in the impurity band is determined by hopping between localized states. For electric fields F greater than 10 v/cm, we have observed nonohmic conductivity over the temperature range. Since the chemical potential lies well below the conduction band ( mu less than E//c) and the temperature is low (k//BT less than E//c), we assume that the nonohmic conduction is associated with a hopping mechanism.