Impurity interaction and the metal-non-metal transition in extrinsic semiconductors

Abstract

The problem of interaction between randomly distributed impurities in semiconductors 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.