An Innovative Model for Electronic Band Structure Analysis of Doped and Un-Doped ZnO

Abstract

An empirical pseudopotential method, in conjunction with virtual crystal approximation and the compositional disorder effect, is exploited to extract the full electronic band structure of various ZnO thin films to ensure excellent agreement with the experimental results, and to compare with the theoretical results obtained on the basis of various density functional theories. The lattice parameters obtained through x-ray diffraction (XRD) studies have been used to characterize the full electronic band structure of various ZnO thin films. The whole work reported here has been carried out using the TNL FullBandTM simulator (Tech Next Lab). The impact of intrinsic and extrinsic doping and the formation of polycrystalline planes in thin film samples on the band gap parameter have been analyzed in terms of the internal structure factor, u. The rigorous analysis of crystalline and polycrystalline samples show that the band gap value is strongly dependent on the internal structure parameter, u. The u value has been found to be significantly affected by lattice disorder generated by the formation of various defects and polycrystalline planes in the thin films. An innovative model demonstrating the relationship between the alloy disorder effect and the internal parameter is reported. With the help of an innovative model, the value of alloy disorder parameters, P, have been extracted for undoped and 1, 2, and 3 at% Cd-, Sr-, and Fe-doped ZnO thin film samples, respectively. Reasonable agreement has been obtained between the reported and experimental optical band gap results. The results reported in the current article show superiority against previously theoretical results based on first-principles methods.