Realistic tight-binding model for the electronic structure of II-VI semiconductors

Abstract

We analyze the electronic structure of group II-VI semiconductors obtained within LMTO approach in order to 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 a nearest-neighbor sp 3 d 5 model is fairly sufficient to describe to a large extent the electronic structure of these systems over a wide energy range, obviating the use of any fictitious s * orbital. The obtained hopping parameters obey the universal scaling law proposed by Harrison, ensuring transferability to other systems. Furthermore, we show that certain subtle features in the bonding of these compounds require the inclusion of anion-anion interactions in addition to the nearest-neighbor cation-anion interactions.PACS 71.20.Nr

Tight-binding model for semiconductor nanostructures

“…This corresponds to Harrison's 54 d −2 rule, the validity of which has been demonstrated for II-VI-materials by Sapra et al 55 . More sophisticated ways to treat the scaling of the interatomic matrix elements, e.g.…”

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

“…We have also carried out a similar analysis on all the II-VI semiconductors starting with the more accurate FP-LAPW results as inputs compared to the previous approach. 9 As these results are found to be slightly different and possibly more accurate in comparison to the earlier results, the new parameter values for the II-VI series are also reported here.…”

“…5, where we present the fits to the ab-initio band dispersions within three different parameterized TB models, namely (a) Ga sp 3 -As sp 3 d 5 basis with Ga-As and As-As interactions; (b) Ga sp 3 s * -As sp 3 d 5 basis with Ga-As and As-As interactions; and (c) Ga sp 3 -As sp 3 d 5 basis with Ga-As, Ga-Ga and As-As interactions. As we have a new set of parameter values (Table II) with a slightly different TB model for the II-VI series compared to the earlier report, 9 we have carried the electronic structure calculations for the nanocrystals of all these II-VI compounds also, for the sake of completion.…”

“…Hence, the need for a physically sound, minimal model without any fictitious orbital and supported by accurate parameterization is required to be able to provide realistic descriptions of both valence and conduction bands in contrast to simulating only the bandgap of these semiconductors. Our attempts 9,12 in this direction on the II-VI semiconductors suggest that much of the difficulties arise from inaccurate parameterization of the bulk band structures. In order to overcome these difficulties, we carried out a detailed analysis of the bulk band structure obtained within the highly accurate FP-LAPW method, supported by the recently developed new generation Muffin-Tin Orbital (NMTO) method 15 to obtain physical, realistic and minimal model with accurate parameterizations.…”

Synthesis of solid solutions of Cd1−xZnxS nanocrystals in the channels of mesostructured silica films

“…Recently, Sapra and Sarma 37 evaluated the electronic structure of II-VI semiconductor nanocrystals (between 5 and 80 Å ) using a modified tight-binding model (TBM), developed by the same group, for bulk II-VI semicoductors. 38 The variations in the band gap difference between the nanocrystals and bulk crystals with the diameter of the nanocrystals were best fit to an empirical formula, DE g = a 1 e 2d/b 1 + a 2 e formula. Notice that the variations in the band gap with respect to the particle size in both CdS and ZnS, are very similar.…”