Self-assembled Ge/Si nanoislands: effect of argon flow and radio frequency power

Abstract

The growth of a germanium–silicon (Ge/Si) heterostructure using radio frequency (rf) magnetron sputtering under optimized conditions is performed. High-density self-assembled Ge nanoislands ∼14 nm in size are obtained directly on Si(100) under 10 sccm argon (Ar) flow and 100 W rf power. The surface roughness and number density of nanoislands revealed by atomic force microscopy are found to be in the range of 3.7–0.6 nm and 45 × 102–20 × 102 μm−2, respectively. An increase in Ar flow and rf power leads to an enhancement of defects, anti-sputtering of the deposited islands and a decrease in the sample quality. X-ray diffraction is used to measure the strain, which is found to be close to the lattice misfit of Ge and Si. It shows the carefully controlled growth condition with minimum density of dislocation. Room temperature photoluminescence exhibits a very strong blue–violet peak at 3.2 eV, which is attributed to the transition from excited triplet level to grand-state singlet level.