Computational study of electronic, magnetic, and optical properties of Fe(II) mono-doped and (Fe(II), Al) co-doped ZnTe

Abstract

Future information technology will rely mainly on spin-related optical properties; however, these properties require microscopic anti-ferromagnetic coupling, ferromagnetic coupling between d-states, or magnetic interaction between transition metal ions and excitons, all of which are poorly understood in these diluted magnetic semiconductors (DMS). In the present work, we performed first-principles calculations to study the magnetic, opto-electronic properties of Fe(II)-doped ZnTe. The results show that Fe(II) doping at the Zn site changes the ground state of ZnTe from non-magnetic to magnetic, with total magnetization of 4 μB. The observed competing ferro- and anti-ferromagnetism in Fe(II)-doped ZnTe can be described on the basis of the RKKY-exchange process. However, the electron introduced by Al co-doping can change the most stable configuration C-1 from AFM to FM state and an estimated curie temperature above room temperature is obtained. The optical properties of pure ZnTe and doped samples have been calculated, and we find that the bandgap (2.14 eV) of ZnTe is shifted to a lower energy with the increase in Fe(II) doping. The spin-allowed d-d transition of Fe ion in the tetrahedral crystal field is observed in the infra-red region of light. Furthermore, the correlation of magnetic coupling of Fe-ions with optical bandgap energy and d-d intra-band transition bands of Fe(II) has been investigated, and we find that the optical bandgap and spin-allowed d-d transition are blue shifted (red-shifted) in AFM (FM) coupled Fe-ion systems, supporting the experimental observations. The improved opto-electronic and magnetic properties of Fe(II)-doped ZnTe by n-type (Al) co-doping provide insight into the potential applications of these materials in spin-related photonic and spintronic devices such as photovoltaics and remote sensing.