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 obtainedwithin full potential linearized augmented plane wave (FP-LAPW) method andarrive at a realistic and minimal tight-binding model, parameterized to providean accurate description of both valence and conduction bands. It is shown thatcation sp3 - anion sp3d5 basis along with the next nearest neighbor model forhopping interactions is sufficient to describe the electronic structure ofthese systems over a wide energy range, obviating the use of any fictitious s*orbital, employed previously. Similar analyses were also performed for theII-VI semiconductors, using the more accurate FP-LAPW method compared toprevious approaches, in order to enhance reliability of the parameter values.Using these parameters, we calculate the electronic structure of III-V andII-VI nanocrystals in real space with sizes ranging upto about 7 nm indiameter, establishing a quantitatively accurate description of the band-gapvariation with sizes for the various nanocrystals by comparing with availableexperimental results from the literature.