New mechanism of impurity conduction in lightly doped crystalline noncompensated silicon

Abstract

It is found that the plastic deformation of lightly doped crystalline silicon samples (N<6×1016 cm−3) with a low compensation (K∼3×10−2) gives rise to nonohmic conduction σM in electric fields that differs radically from conventional hopping conduction via the ground states of impurities (σ3). The values of σM can exceed values of σ3 by a factor of 103−105. The value of σM and its dependence on the electric (E) and magnetic (H) fields can be controlled by varying the density of dislocations and the mode of thermal sample treatment. A strong anisotropy of σM is observed in samples with oriented dislocations: the conductivities along and across dislocations can differ by a factor of 104. The results are explained by the occurrence of conduction via the H−-like states of impurities concentrated in the vicinity of dislocations. The levels of these states lie between the upper and the lower impurity Hubbard bands.