First principle investigation of structural, electronic and optical properties of Er-doped (ZB) ZnO using modified Becke-Johnson exchange potential. E.A. Alkahtani, A.E. Merad, A. Benosman M. R. Boufatah Theoretical Physics Laboratory, Department of physics, Sciences faculty, A.Belkaid University, Tlemcen , Algeria Email address: ahmedissam09@gmail.com Email address: aemerad@gmail.com Abstract: In this work, we investigated the effect of Er, as a dopant element, on physical properties of ZnO. Structural, electronic and optical properties are obtained for 25% of Er doped ZnO in hypothetical zincblend structure. This study done using Density Functional Theory (DFT) with generalized gradient approximation (GGA) and modified Becke-Johnson exchange potential (mBJ). It found that, the calculated energy band gap and the lattice parameter of pure ZnO are close to the experimental ones and was in a good agreement with other theoretical calculations. It also shown that, the incorporation of Er in ZnO affects considerably the electronic and optical properties. For example, the optical energy gap has increased by 83% under Er doping. From imaginary dielectric function, we established that red shift also achieved under Er doping indicating the importance of its 4f donor occupied states. Keywords: Er-doped ZnO; FP-LAPW; mBJ potential; Electronic structures; Optical properties. I. INTRODUCTION Recently, the ZnO presented an interesting subject for doping with various elements such as transition and noble metals. This is of course very suitable to improve the optoelectronic and photocatalytic properties because the incorporation of dopants generates lattice defects and changes consequently the band gap energy [1]. In particular, the doping with rare-earth elements has been extensively investigated, experimentally as well as theoretically. Poongodi et al [2] deposited nanostructured Nd doped ZnO thin films on glass substrate by a sol–gel spin coating technique. The results show the degradation of methylene blue dye and the decrease in grain size and light absorption over an extended visible region by Nd ion doping in ZnO film, contributed equally to improve the photocatalytic activity. Honglin et al [3] prepared the ZnO nanopowders doped with (La, Er, and Nd) rare earth by chemical method. The photoluminescence (PL) measurement revealed that pure and REs doped ZnO had different I UV /I DLE ratios, and the absorption spectra of doped ZnO exhibited enhanced optical absorption in visible region. In particular, the attractive interest of Erbium (Er)-doped semiconductors in optical applications such as light-emitting and laser diodes, is because of the sharp photoluminescence (PL) at 1.54 μm from the intra-4f shell transition in Er 3+ ions [4]. The majority of works carried out the above properties at low temperature (77 K) precluding their use at room temperature [5]. However, few reports for Er doped ZnO in thin film or wurtzite phases have been experimentally investigated showing the PL spectra at room temperature, as given in the work of Honglin [3]. In this work, we aimed to study the effect of Er doped ZnO in comparison with pure ZnO in paramagnetic phase that is observed at high temperature. Structural, electronic and optical properties are obtained for 25% of Er doped ZnO in zinc blend structure by caring out a first principles calculations based on density functional theory (DFT). II. COMPUTATIONAL DETAILS All calculations have been carried out using density functional theory with help of the full-potential linearized augmented plane-wave (FP-LAPW) method as implemented in WIEN2k package ,[6,7] which self-consistently finds the eingen values and eingen function of the Kohn-Sham [8]equations for the system. Fig.1: Unit supercell of zincblende Er doped ZnO.