IMPURITY INTERACTION AND THE METAL-NON-METAL TRANSITION IN EXTRINSIC SEMICONDUCTORS

The problem of interaction between randomly distributed impurities in semi-conductors is discussed and a ‘ cluster ’ model of the metal-non-metal transition is proposed. This might help to resolve the recent controversy about the origin of the far-infra-red absorption in uncompensated, highly doped semiconductors, and to understand the role of disorder in the transition from local to non-local behaviour in random systems. It is shown, in particular, that the impurity interaction gives rise to a pronounced tail on the high-energy side of the lower Hubbard band. © 1979 Taylor & Francis Ltd.