The onset of secondary slip in the plastic deformation of tetrahedrally bound semiconductors

The shape of the stress–strain curves of tetrahedrally coordinated semiconductors strongly depends on temperature. Prominent features such as the yield point and the recovery-controlled stage III exhibit Arrhenius-law behavior with characteristic activation energies, which may be connected with microscopic dislocation processes. The transition from stage I to stage II of the stress–strain curve, however, has not found much interest, although reliable data sets with well-defined temperature and strain-rate dependences are available. In the present work data from nine undoped and doped semiconductors are analysed. The behavior of the transition stress τII clearly resembles that of the lower yield stress, although the resulting parameters are somewhat different. The transition is eventually traced back to the onset of secondary glide in the course of constant strain-rate deformation. The results are discussed in terms of microscopic processes occurring in the dislocation core, and are in agreement with recent findings of positron annihilation spectroscopy.