Bandstructure and photoluminescence of SiGe islands with controlled Ge concentration

The dependence of the photoluminescence (PL) emission wavelength of SiGe islands embedded into a Si matrix on their Ge concentration and gradient was investigated. Intense PL signals at wavelengths that can be shifted over most of the telecom wavelength range (1.38–1.77 μm) by varying the Ge concentration were observed. Using the structural island parameters determined by AFM, TEM, and a careful analysis of X-ray reciprocal space maps, good agreement between calculated and measured PL emission wavelength was achieved, indicating that by combining PL and X-ray experiments, an accurate determination of the Ge concentration and a quantitative modeling of the bandstructure of the SiGe islands is possible.