This paper will review the theory of hopping conductivity and present some recent results for many-electron systems. In strongly disordered semiconductors at low temperatures the dominant transport process is electron hopping. This mechanism is relevant to conduction in amorphous semiconductors, impurity bands and some conducting polymers. A consistent theory of the process in a one-electron approximation is obtained in a rate equation approach and an approximate solution is given by the Extended Pair Approximation. Its results are consistent with large scale computer simulations and experiments. For the acceptor conductivity a universal scaling relationship can be inferred and this allows a strong classification of systems to be made. Impurity conduction in the presence of electron-electron interactions is studied by analytical and numerical techniques. At low temperatures there is a Coulomb gap in the density of states. Simulations of the percolation problem show the gross features of the behavior of the dc conductivity. It may be inferred that there is an effective one-electron mechanism in which the Coulomb gap has questionable importance.

Date Published: 1 February 1992
PDF: 10 pages
Proc. SPIE 1523, Conference on Physics and Technology of Semiconductor Devices and Integrated Circuits, (1 February 1992); doi: 10.1117/12.56994

Published in SPIE Proceedings Vol. 1523:
Conference on Physics and Technology of Semiconductor Devices and Integrated Circuits
B. S. V. Gopalam; J. Majhi, Editor(s)