Anomalous luminescence peak shift of SiGe/Si quantum well induced by self-assembled Ge islands

Strain effects in a strained SiGe/Si quantum well induced by self-assembled Ge islands have been studied by varying the Ge coverage. The strain by the Ge islands induces a complicated behavior in photoluminescence spectra depending on the Ge coverage. The Ge islands give the enhanced local strain to the underlying structures with the increase of the Ge coverage, at the early stage of the growth. However, as the Ge coverage increases the enhanced local strain does not continue being reinforced but is limited after once being retrogressed. These results are discussed in terms of elastic deformation due to the lattice mismatch between Si and Ge and the lattice relaxation in Ge islands.