Electronic structure of and quantum size effect in Ⅲ-Ⅴ and Ⅱ-Ⅵ semiconducting nanocrystals using a realistic tight binding approach

摘要

We analyze the electronic structure of group Ⅲ-Ⅴ semiconductors obtained within full potential linearized augmented plane wave (FP-LAPW) method and arrive at a realistic and minimal tight-binding model, parametrized to provide an accurate description of both valence and conduction bands. It is shown that the cation sp~3-anion sp~3d~5 basis along with the next nearest neighbor model for hopping interactions is sufficient to describe the electronic structure of these systems over a wide energy range, obviating the use of any fictitious s~* orbital, employed previously. Similar analyses were also performed for the Ⅱ-Ⅵ semiconductors, using the more accurate FP-LAPW method compared to previous approaches, in order to enhance reliability of the parameter values. Using these parameters, we calculate the electronic structure of Ⅲ-Ⅴ and Ⅱ-Ⅵ nanocrystals in real space with sizes ranging up to about 7 nm in diameter, establishing a quantitatively accurate description of the bandgap variation with sizes for the various nanocrystals by comparing with available experimental results from the literature.