Formation Dirac point and the topological surface states for HgCdTe-QW and mixed 3D HgCdTe TI

Faculty of Mathematics and Natural Sciences, Centre for Microelectronics and Nanotechnology, University of Rzeszów, Pigonia 1, 35-959 Rzeszów, Poland

^* Corresponding author: marmi@ur.edu.pl

Published online: 15 December 2016

Abstract

In this paper the results of numerical calculations based on the finite difference method (FDM) for the 2D and 3D TI with and without uniaxial tensile strain for mixed Hg_1-xCd_xTe structures are presented. The numerical calculations were made using the 8×8 model for x from 0 up to 0.155 and for the wide range for the thickness from a few nm for 2D up to 150 nm for 3D TI as well as for different mismatch of the lattice constant and different barrier potential in the case of the QW. For the investigated region of the Cd composition (x value) the negative energy gap (E_g=Γ₈-Γ₆) in the Hg_1-xCd_xTe is smaller than in the case of pure HgTe which, as it turns out, has a significant influence on the topological surface states (TSS) and the position of the Dirac point for QW as well as for 3D TI. The results show that the strained gap and the position of the Dirac point against the Γ₈ is a function of the x-Cd compounds in the case of the 3D TI as well as the critical width of the mixed Hg_1-xCd_xTe QW.