Dislocation-related photoluminescence peak shift due to atomic interdiffusion in SiGe/Si

Abstract

Low-temperature photoluminescence (PL) spectroscopy was used to study electronic states associated with threading dislocations (D lines) in strain-relaxed Si1−xGex layers. The structures investigated were grown by ultrahigh vacuum chemical vapor deposition at 550 °C and consist of a Si(001) substrate, followed by a stepwise graded buffer layer, followed by a thick uniform composition Si1−xGex layer. The PL peak positions of the four D lines after isochronal annealing at temperatures between 600 and 800 °C were measured. We show that the large energy shift of the D1 line is due to a change in the local band gap energy at the dislocation core due to strain-driven diffusion of Ge atoms away from the dislocation core with an activation energy Ea, which varies with Ge mole fraction x.