Spin-peierls transition in the random impurity sublattice of a semiconductor

A study of electron spin resonance in uncompensated Ge:As semiconductor samples in the vicinity of the insulator-metal second-order phase transiti on reveals that the interaction of spins localized at As atoms brings about a distortion of the crystal lattice and enhances the localization. This effect occurs in the range of electron concentrations n = 3 × 1017—3.7 × 1017 cm-3, just below the critical point of the phase transition. The effect is explained in the context of a model considering the spin-Peierls transition in the random impurity sublattice of the semiconductor, and its features, as compared to other known materials where the spin-Peierls transition is observed, are understood.