Structural, electronic and optical properties of the wide-gap Zn1−xCdxTe ternary alloys

The II–VI compounds CdTe and ZnTe form a complete series of solid solutions with a cubic Zinc Blende structure. The room temperature band gap of these materials can be tuned from 1.5 eV in CdTe to 2.3 eV in ZnTe by controlling the alloy composition. This material is used as the window layer in thin-film solar cells. Using first-principles calculations, we investigated the structural and electronic properties of two binary CdTe and ZnTe for several compositions with various ordered structures (Cu3Au, luzonite) of Zn1−xCdxTe alloys using the theory of order–disorder transformation. An investigation was also conducted using the first-principles total-energy formalism based on the hybrid full potential augmented plane wave plus local orbital (APW+lo) method, within the local-density approximation (LDA) for the exchange and correlation potential. The 3d orbitals of the Zn atoms and 4d orbitals of the Cd atoms were treated as valence bands in every case. We analyzed the effect of alloying a small amount of ZnTe with CdTe; the fundamental direct band gap energy of the alloys was found to decrease per atomic percent of cadmium.