Electronic and structural properties of A Al2Se4 (A=Ag, Cu, Cd, Zn) chalcopyrite semiconductors

We have studied the structural and electronic properties of defect chalcopyrite semiconductors A Al2Se4 (A =Ag, Cu, Cd, Zn) using density functional theory (DFT) based first principle technique within tight binding linear muffin-tin orbital (TB-LMTO) method. Our calculated structural parameters such as lattice constants a and c , tetragonal distortion (η=c/2aη=c/2a) are in good agreement with experimental work. Anion displacement parameters, bond lengths and bulk modulus are also calculated. Our band structure calculation suggests that these compounds are direct band gap semiconductors having band gaps 2.40, 2.50, 2.46 and 2.82 eV for A Al2Se4 (A=Ag, Cu, Cd, Zn) respectively. Calculated band gaps are in good agreement with other experimental and theoretical works within LDA limitation. We have made a quantitative estimation of the effect of p–d hybridization and structural distortion on the electronic properties. The reduction in band gap due to p–d hybridization is 19.47%, 21.29%, 0% and 0.7% for A Al2Se4 (A=Ag, Cu, Cd, Zn) respectively. Increment of the band gap due to structural distortion is 11.62%, 2.45%, 2.92% and 9.30% in case of AgAl2Se4, CuAl2Se4, CdAl2Se4 and ZnAl2Se4 respectively. We have also discussed the bond nature of all four compounds.