Stability and bandgap of semiconductor clusters

Using a parameterized density-functional method we have studied the structural and electronic properties of different II–VI and III–V semiconductor clusters. We studied finite parts of the zincblende and wurtzite crystal structure for CdS, CdSe, InP, and ZnO and allowed the structures to relax to the closest total-energy minimum. Both stoichiometric and non-stoichiometric naked clusters were considered. We found (i) that the relative stability of the zincblende- and the wurtzite-derived clusters depends on the size of the structure, (ii) that the total-energy per atom is a non-smooth function of the size, and (iii) a correlation between the size of the HOMO–LUMO bandgap and the stability of the cluster. The implications of these results for the experimental analysis of the size distributions are discussed.