Theoretical investigation of band gap and optical properties of ZnO 1x Te x alloys (x = 0, 0.25, 0.5, 0.75 and 1) N.A. Noor a , S. Ali a , G. Murtaza b , M. Sajjad c , S.M. Alay-e-Abbas d,e , A. Shaukat e , Z.A. Alahmed f , A.H. Reshak g,h,⇑ a Department of Physics, University of the Punjab, Quaid-e-Azam Campus, Lahore 54590, Pakistan b Centre for Advanced Studies in Physics, G.C. University, Lahore 54000, Pakistan c School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China d Department of Physics, GC University Faisalabad, Allama Iqbal Road, Faisalabad 38000, Pakistan e Department of Physics, University of Sargodha, Sargodha 40100, Pakistan f Department of Physics and Astronomy, King Saud University, Riyadh 11451, Saudi Arabia g New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 614 Pilsen, Czech Republic h Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis, Malaysia article info Article history: Received 22 March 2014 Received in revised form 27 May 2014 Accepted 13 June 2014 Keywords: Special quasi-random structure Rock-salt (RS) Zinc-blende (ZB) ZnO 1x Te x alloys abstract In this study, the special quasi-random structure (SQS) approach has been considered for structural, elec- tronic and optical properties of rock-salt (RS) and zinc-blende (ZB) phases of ZnO 1x Te x (x = 0, 0.25, 0.5, 0.75 and 1) using density functional theory. The Wu–Cohen generalized gradient approximation (GGA) has been employed for optimizing the lattice parameters (a 0 ) and bulk moduli (B 0 ) in both phases which show reasonable agreement with numerous theoretical and experimental results. To compute the band gaps with high degree of precision, we employed Engel–Vosko GGA and modified Becke and Johnson local density approximation (mBJLDA) functionals. In the RS phase, metallic nature of the compounds under investigation is evident for 0.25 < x < 1, whereas direct band gap appears at all concentrations in ZB phase. The density of states (total and partial) are presented to comprehensively analyze the electronic structure of all compounds. Contrary to earlier theoretical studies, the mBJLDA band gap values for the end binaries appear to be significantly improved showing overall better agreement with the experimental data. The optical properties of ZnO 1x Te x alloys in the ZB phase are also discussed in terms of dielectric function which show their potential utilization in optoelectronic devices. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction The high complexity of pristine and defective forms of II–VI wide-gap semiconductors has made these materials one of the hot topics in the current condensed matter research [1–6]. Among these semiconductors, ZnO stands out for future technological needs due to its suitability for various electronic, optical and mag- netic devices which has been the reason behind numerous exper- imental and theoretical investigations for this material [1,7]. The increasing interest in ZnO originated from its promising applica- tions in spintronic and opto-electronic devices. Moreover, ZnO is already being used in applications which range from fabrication of solar cells, light emitting diodes (LEDs), ultraviolet (UV) opto- detectors to piezo-electronic devices and thin film transistors [1,2,8–11]. In addition, the attractive properties of ZnO nano- crystals, such as hysteresis above ambient, lasing ability in ultravi- olet and visible region at room temperature as well as selective sensing of glasses are well understood and already playing a crucial technological role [12–14]. The possibility to grow large size ZnO crystal and wafer by modern techniques has struck an immediate chord with researchers interested in its industrial use [15]. Sub- stantial progress has been made in understanding this material and remarkable new properties of polycrystalline and nanocrystal- line ZnO are discovered which are very important from technolog- ical point of view [5,8,12,16–20]. On the other hand, II–VI wide-gap semiconductors ZnTe has attracted a great deal of attention being a natural candidate for opto-electronic device applications like detectors, light emitting diodes (LEDs) and window material for CdTe based solar cells [21–23]. Various fabrications techniques such as molecular beam epitaxy (MBE), thermal vacuum evaporation (TVE), vapor phase deposition (VPD) and electrochemical deposition have http://dx.doi.org/10.1016/j.commatsci.2014.06.017 0927-0256/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 6 14 Pilsen, Czech Republic. Tel./fax: +420 777729583. E-mail address: maalidph@yahoo.co.uk (A.H. Reshak). Computational Materials Science 93 (2014) 151–159 Contents lists available at ScienceDirect Computational Materials Science journal homepage: www.elsevier.com/locate/commatsci