Recent experiments on deformation of semiconductors show an abrupt change in the variation of the critical resolved shear stress, τy
, with temperature, T. This implies a change in the deformation mechanism at a critical temperature Tc
. In the cases examined so far in our laboratory and elsewhere, this critical temperature appears to coincide approximately with the brittle-ductile transition temperature, TBDT
. In this paper, the deformation experiments performed on the wide bandgap semiconductor, 4H-SiC, over a range of temperatures and strain rates are described together with the characterization of induced dislocations below and above Tc
by transmission electron microscopy. Based on these results, and those of Suzuki and coworkers on other compound semiconductors, some understanding of the different mechanisms operating at low and high temperatures in tetrahedrally coordinated materials has been gained, and a new model for their brittle-ductile transition has been proposed.