Charged dislocations and the plastic deformation of II-VI compounds

Abstract

The flow of charge associated with the plastic deformation of monocrystals of ZnO, ZnS, ZnSe, ZnTe, CdS, CdSe and CdTe has been studied both in the dark and under illumination. It ariscs from the motion of charged dislocations on either the shuffle (Aa) or the glidc (aB) set of (111) or (0001) planes. The magnitude of the charge has been determined for each material. Most of the materials are n-type and have negatively charged dislocations, but in p-type ZnTe the dislocations are positively charged. The ionic charge of these dislocations is discussed, but this charge will be changed by the capture or loss of electrons. The experimental results are explained by a modification to the model of Kirichenko. Petrenko and Uimin (1978) in which there is n dynamic equilibrium between electrons in levels on dislocations, at point defects and in the conduction band. The dislocation charge in the dark increases with the energy gap in a manner that is consistent with this theory, Both tee dislocation charge and the flow stress are increased by illumination, and for the whole series of Compounds there is a strong correlation between the flow stress and the dislocation charge.