Structure changes caused by the stress gradient in subsurface layers of germanium single crystals

Structural defects in Ge single crystals at low temperature caused by the stress gradient were investigated by optical and electron microscopy. At T = 600 K the cyclic deformation by uniaxial pressing causes sliding of the dislocations along directions <110> in. planes {111}, which begins in the subsurface layers at the edges of the samples. At lower temperatures the intensive generation and migration of point defects from concentrators promotes dislocation movement by creeping. The thickness of the subsurface layer with dislocations after repeated loading at 300 K is 5 - 7 mum and the depth of the deformation clusters reached 50 mum. These results are confirmed by optical microscopy and electrical measurements.