Investigation of the optical and structural characteristics of Ge self-assembled quantum dots grown directly on Si substrates and on strain relaxed Si/sub 0.9/Ge/sub 0.1/ buffer layers

The optical and structural properties of Ge quantum dots (QDs) of varying size grown on Si substrates with and without a partially relaxed Si/sub 0.9/Ge/sub 0.1/ buffer layer, were investigated by means of photoluminescence and atomic force microscopy. A random, bimodal QD size distribution was observed for Ge QDs directly grown on Si substrates, while a well-aligned, unimodal size QD distribution was observed for Ge QDs with the Si/sub 0.9/Ge/sub 0.1/ buffer layer. Quantum confinement effects with dot size variation were evident from PL studies. A blue shift of the Ge QD emission energy with increasing excitation power is ascribed to the band bending at the type-II Si/Ge interface.