Nucleation chronology and electronic properties of In(As,Sb,P) graded-composition quantum dots

We have studied nucleation process and electronic properties of graded-composition quantum dots (GCQDs) grown from In-As-Sb-P in the liquid phase for application in mid-infrared devices like photoresistors or photoconductive cells. The GCQD ensemble exhibits diameters of 10-120 nm and heights of 2-20 nm. Compositional grading is a typical feature of quantum dots grown in liquid-phase epitaxy (LPE) and our GCQDs exhibit increasing Sb content to their top with a maximum Sb content of 20% and a decreasing P content with its maximum of approx. 15% at their bottom. We have performed systematic simulations of the electronic properties of the GCQDs using an eight-band k·p model taking strain and built-in electrostatic potentials into account. Here we have studied the influence of height and diameter of the GCQDs on their absorption spectra as close as possible to the systems observed in experiment. Combining data from the height and diameter distribution of the GCQDs ensemble with absorption energies of similar systems obtained from the simulations, we obtain an absorption spectrum of the ensemble. The simulated spectrum yields a maximum absorption at 3.829 μm, which is extremely close to the one observed in experiment. Correspondingly, our simulation setup can be employed for a theory-guided design of GCQDs suited to the requirements of specific devices.