Predicting Size Distributions of Ge Nanodots from Their Photoluminescence

Abstract

Self-assembled Ge nanodots were fabricated by in situ thermal annealing of a thin amorphous Ge layer deposited by molecular beam epitaxy on a mesoporous layer on Si(001). With average dot diameters of about , the dot photoluminescence (PL) appeared primarily as a wide near-infrared band near . Employing a tight binding theoretical model, we have transformed the energy-dependent PL spectrum into a dependence on dot size. The peak energy of the PL band reflects the average dot size and its shape depends on the dot size distribution, including, for the smaller diameter dots, a bandgap enlargement due to quantum confinement. Using the dot sample PL and our previously established dependence of the PL quantum efficiency on dot diameter, we show that it is possible to make a limited prediction of the size distribution of Ge dots, which we compare with the actual size distribution obtained from atomic force microscopy.