On transition temperatures in the plasticity and fracture of semiconductors

Recent experiments on deformation of semiconductors show an abrupt change i n the variation in the critical resolved shear stress tau (Y) with temperat ure T. This implies a change in the deformation mechanism at a critical tem perature T-c. In the cases examined so far in our laboratories (Case Wester n Reserve University and Poitiers) and elsewhere, this critical temperature appears to coincide approximately with the brittle-to-ductile transition t emperature T-BDT. In this paper, new deformation experiments performed on t he wide-bandgap semiconductor 4H-SiC over a range of temperatures at two st rain rates are described together with a transmission electron microscopy c haracterization of induced dislocations below and above T-c. Based on these , and results recently reported on a few III-V compound semiconductors, a n ew model for the deformation of tetrahedrally coordinated materials at low and high temperatures is proposed, and the relation of the transition in de formation mode to the transition in fracture mode (brittle to ductile) is d iscussed.