The Electronic Properties of Cu 2 ZnGeS 4 , Cu 2 CdGeSe 4 , and Cu 2 CdSnSe 4 Calculated by GGA+U Technique

Abstract

Cu2ZnGeS4, Cu2CdGeSe4, and Cu2CdSnSe4 crystallizes in the tetragonal (I-42m) stannite structure. Their electronic properties have been studied using the pseudopotential method within the framework of the density functional theory. For exchange and correlation, the GGA+U was used in conjunction with the projector augmented wave. The calculations predicted the three materials as semiconductors with indirect band gap value of 1.22 eV, 1.65 eV, and 1.92 eV for Cu2ZnGeS4, Cu2CdGeSe4, and Cu2CdSnSe4 respectively. The partial density of states calculations showed that for Cu2ZnGeS4 compound, Se-4p is the dominate state at the top of the valence band while Ge-4s is the principal state at the bottom of the conduction band. Similarly, the top of the valence band for Cu2CdGeSe4 is mainly of Ge-4s and Se-4p states while the bottom of the conduction band is populated mostly by Ge-3d and Ge-4p states. For Cu2CdSnSe4, VBM is composed mainly of Se-4p and CBM is composed of Se-5s and Cd-4d states.

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