Anomalous x-ray scattering study of the growth of inverted quantum hut structures in a Si-Ge superlattice emitting strong photoluminescence

Abstract

The growth process of germanium inverted quantum hut (IQH) structures, which are embedded in a silicon lattice, has been studied using anomalous x-ray scattering techniques. These self-assembled IQH structures exhibit strong photoluminescence (PL) although the number density of the huts is rather small. We show here that these IQH structures form by the intermixing of germanium with previously deposited silicon producing an intriguing composition variation that keeps the out-of-plane lattice parameter of the alloy almost constant. We have identified a zero strain cubic structure, which extends towards the tip of these IQHs to accommodate large-scale interdiffusion of germanium in silicon lattice. A substantial increase in intensity of the PL peak at around 0.8 eV as the temperature is lowered from 70 to 10 K and a corresponding activation energy of 49 meV indicates that photon induced carriers are predominantly captured at the tip of the embedded quantum hut structures.