First principle calculation of Cadmium Telluride using density functional theory

Abstract

CdTe is a wide band gap semiconductor belonging to group II-VI. It is commonly used in light emitting diodes (LED) and many optoelectronic devices fabrications. It is obvious that many body problems are complex and a piece challenging to solve. Due to this the state of motion cannot be solved analytically for systems in which three or more masses are interact. To solve this many body problems, the Density Functional Theory is preferred as an accurate and reliable tool. The first principle calculation based on density functional theory (DFT) was employed to investigate the electronic and structural properties of hexagonal(wurtzite) and zincblende CdTe using quantum ESPRESSO package. A number of convergence test were performed to establish the optimal value of various parameters in the numerical calculations. Firstly, the total minimum energy of CdTe per atom was calculated as a function of cutoff energy and k-points sampling. Secondly, the optimal lattice constants of CdTe was calculated for a series of possible parameters using the results obtained from energy convergence test (i.e, for wurtzite 110 Ry and 7×7×7 k-points, for zincblende 110 Ry and 4×4×4 k-points). Moreover the band structure and density of states of CdTe have been calculated based on the frame work of density functional theory. The results of calculations show that the total minimum energy of CdTe per atom is monotonically decreasing with increasing cutoff energy due to variational principle. However, this trend can not be predicted from increasing the k-point sampling. The computational value of the equilibrium lattice constant for wurtzite was A = 4.684 A, C = 7.684 ˚ A and for zincblende was 6.60 ˚ A. The obtained ˚ result was over estimated as compared to the experimental result. The computed values of band structure and density of states of wurtzite Cadmium Telluride was 0.595 eV and 0.58 eV respectively. The computed values of band structure and density of states of zincblende Cadmium Telluride was 0.605 eV and 0.79 eV respectively.