Investigation of the optical and structural characteristics of Ge self-assembled quantum dots grown directly on Si substrates and on strain relaxed Si0.9Ge0.1 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_0.9Ge_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_0.9Ge_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.