Electronic and optical properties of mixed Be-chalcogenides

The electronic and optical properties of BeSxSe1−x, BeSxTe1−x and BeSexTe1−x, (0≤x≤1) are studied using the highly accurate modified Beck and Johnson (mBJ) potential. The binary Be-chalcogenides are wide and indirect band gap semiconductors and hence they are not efficient materials for optoelectronics. In order to modify them into optically active materials, the anion chalcogen atoms are partially replaced by other chalcogen atoms like BeSxSe1−x, BeSxTe1−x and BeSexTe1−x (0≤x≤1). The modified ternary compounds are of direct band gap nature and hence they are optically active. Some of these direct band gap materials are lattice matched with silicon and can possibly replace Si in semiconductor devices. Keeping in view the importance of these materials in optoelectronics, the optical properties of BeSxSe1−x, BeSxTe1−x and BeSexTe1−x in the full composition range are investigated. It is found that these materials are transparent in the IR, visible and near UV spectral regions. The alloys for the most of the concentrations have band gaps larger than 3eV, so it is expected that they may be efficient materials for blue, green and UV light emitting diodes. ► BeS, BeSe and BeTe in the zinc-blende structure are indirect bandgap semiconductors. ► Indirect bandgap semiconductors are optically inactive. ► BeSSe, BeSTe and BeSeTe are direct bandgap compounds. ► Optical properties of these optically active materials are explored. ► Bandgap bowing and band structures of the compounds are also presented.