Analysis of hopping conduction in impurity bands in inversion layers

Percolation arguments are used to develop formulae for hopping conductivity involving localized states distributed over a bandwidth of energies. All possible locations of the Fermi level are treated. When the Fermi level lies in the centre of the band the formulae are used to analyse activated hopping conductivity in an impurity band formed by drifting Na + ions near the Si-SiO2 interface in a MOSFET. All the system parameters may be deduced from the activated conductivity data. The transition to variable-range hopping at lower temperatures may then be predicted. It is found to be in good agreement with the experimental data.