Excitation-dependent photoluminescence in Ge∕Si Stranski-Krastanov nanostructures

Abstract

In Ge∕Si Stranski-Krastanov nanostructures grown by chemical vapor deposition, the authors find ∼30meV/decade photoluminescence (PL) spectral shift toward greater photon energies as excitation intensity increases from 0.1to104W∕cm2. The PL lifetime exhibits strong spectral dependence, and it decreases from ∼20μs at 0.77eVto200ns at 0.89eV. The authros attribute the observed PL spectral shift and shorter PL lifetime at higher photon energies to an increasing contribution from recombination between holes populating excited Ge cluster energy states and electrons in SiGe alloy cluster regions.