Electronic, magnetic and optical properties of Cr and Fe doped ZnS and CdS diluted magnetic semiconductors: revised study within TB-mBJ potential

Transition metal (TM) doping ZnS and CdS have attracted extensive research interests due to their potential spintronic applications. Most of these theoretical and experimental analyses have focused on their wurtzite-type structure. However, few investigations for their zinc-blende-type structure are reported in the literature, especially for their optical properties. Here, we present an in-depth assessment of the electronic structures, magnetic and optical properties of ZnS and CdS semiconductors doped with transition metal atoms (TM) X (X = Cr and Fe) that we have carried out by first principles calculations. On the basis of the GGA approximation, PBEsol and TB-mBJ potentials are used for exchange and correlation potential. The improvement in the energy band gap value, within TB-mBJ potential, is very remarkable indicating that all the studied compounds are wide-band gap materials (Eg >= 3 eV). The magnetic half-metallic band gap, band structures, densities of states and optical properties are analyzed in depth. For the studied compounds, our results show a metallic nature for spin up and keep the semiconductor nature for spin down for Cr atom while a reversed behavior is revealed for Fe atom. The corresponding revised data are proposed following the subsequent TB-mBJ potential. Moreover, the half-metallic band gap Eg(HM) decreases from CdS to ZnS, in opposite to the PBEsol prediction for the both Fe and Cr impurities. New trends and conclusions are then presented showing the impact of this latter potential in improving the values of several studied properties and not limited only to the energy bandgap, as is known. With this potential, the maximum absorption reaches its high energy value. Our results are also compared with available theoretical and experimental values and a good agreement is obtained. We hope that our revised research can be useful for technological applications such as spintronics and photovoltaics.