Degenerate impurity states in hopping conduction

Abstract

Abstract A review of studies on nearest-neighbour hopping (NNH) between impurities, whose ground state (GS) is degenerate or split by the application of a uniaxial stress X or a magnetic field B is presented. The case of acceptors in Ge and Si, whose GS components have different symmetry properties, is discussed in detail. A solution (of the percolation problem involving all the possible transitions between the components of the acceptor GS is provided. For Ge it was preceded by a construction of the acceptor ground state wavefunctions, possessing both a correct symmetry and a correct asymptote behaviour, indispensable for evaluating probabilities of phonon-assisted NNH. For Si the energy diagrams of the accepter GS for various configurations of X and B were obtained and subsequently used in a model calculation. In both Ge and Si the calculation accounted qualitatively for the data.