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

TL;DR

This paper develops a realistic tight-binding model for III-V and II-VI semiconducting nanocrystals, accurately capturing their electronic structure and quantum size effects, validated against experimental data.

Contribution

It introduces a minimal tight-binding approach parameterized from first-principles calculations, improving the description of nanocrystal electronic structures without fictitious orbitals.

Findings

Accurate band-gap variation with nanocrystal size

Validated tight-binding parameters against experimental data

Demonstrated the model's effectiveness over a wide energy range

Abstract

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, parameterized to provide an accurate description of both valence and conduction bands. It is shown that cation sp3 - anion sp3d5 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 upto about 7 nm in diameter, establishing a quantitatively accurate description of the band-gap variation with sizes for the various nanocrystals by comparing with available experimental results from the literature.