Physica B 337 (2003) 363–368 Energy band gaps of Zn 1x Mg x S y Se 1y lattice matched to GaAs Z. Charifi, H. Baaziz, N. Bouarissa* Physics Department, Faculty of Science and Engineering, University of M’sila, 28000 M’sila, Algeria Received 6 November 2002; accepted 10 June 2003 Abstract We report on theoretical study of the energy band gaps for the quaternary alloys Zn 1x Mg x S y Se 1y in conditions of lattice matching to GaAs substrates using simply the empirical pseudopotential method under the virtual crystal approximation which takes into account the effects of compositional disorder. Our results agree generally very well with the available experimental data. It is shown that the band-gap energies of Zn 1x Mg x S y Se 1y are expressed by the parabolic function of the composition considering the bowing parameter and that Zn 1x Mg x S y Se 1y can be a direct or an indirect semiconductor depending on the alloy composition. The Zn 0:35 Mg 0:65 S 0:6 Se 0:4 is predicted to meet requirement of the cladding layer for fabricating blue double heterostructure laser diodes using ZnS 0:06 Se 0:94 as the active layer. r 2003 Elsevier B.V. All rights reserved. PACS: 71.20.b Keywords: Electronic structure; Zn 1x Mg x S y Se 1y ; Lattice matched alloys 1. Introduction The semiconducting materials capable of oper- ating in the short wave length optical range have received an increasing interest, due to their potential for the realization of light-emitting and laser diodes (LDs) encompassing the entire visible- light window. The most promising among these materials are II–VI and nitride semiconductors. To cause double heterostructures (DHs) [1], multi-quantum wells [2] and other structures [3,4] to oscillate in the blue region at room temperature, ZnSe was used for the active layer and ZnSSe was used for the barrier layer [5]. However, the suitable cladding layer of Zn (S)Se for fabricating a blue LD was not identified. This is due to the difference in the band-gap energies of ZnSe and ZnSSe and the conduction-band discontinuity [5,6]. To over- come this shortcoming, Okuyama et al. [5,7,8] have proposed a new material, MgZnSSe, which has the desirable property that its lattice parameter and fundamental band gap can be tuned fairly independently by acting on the compositions x and y: The technological importance of this material requires the knowledge of the band parameters ARTICLE IN PRESS *Corresponding author. Fax: +213-35-686213. E-mail address: n bouarissa@yahoo.fr (N. Bouarissa). 0921-4526/$ - see front matter r 2003 Elsevier B.V. All rights reserved. doi:10.1016/S0921-4526(03)00428-9