Low-temperature photoluminescence spectroscopy was used to study threading dislocations in strain-relaxed SiGe layers. The investigated structures were grown by means of ultra-high vacuum chemical vapor deposition at 550C, and consisted of a Si(001) substrate, followed by a step-wise graded buffer layer, followed by a thick uniform-composition SiGe layer. The photoluminescence peak positions of the four D lines were measured after isochronal annealing (600 to 800C). It was shown that a large energy shift of the D1 line was due to a change in the local band-gap energy, at the dislocation core, due to strain-driven Ge diffusion away from the dislocation core; with an activation energy which varied with the Ge mole fraction.

K.Shum, P.M.Mooney, J.O.Chu: Applied Physics Letters, 1997, 71[8], 1074-6