First-principles study on the effective masses of zinc-blend-derived Cu2Zn−IV−VI4 (IV = Sn, Ge, Si and VI = S, Se)

Abstract

The electron and hole effective masses of kesterite (KS) and stannite (ST) structured Cu2Zn−IV−VI4 (IV = Sn, Ge, Si and VI = S, Se) semiconductors are systematically studied using first-principles calculations. We find that the electron effective masses are almost isotropic, while strong anisotropies are observed for the hole effective masses. The electron effective masses are typically much smaller than the hole effective masses for all studied compounds. The ordering of the topmost three valence bands and the corresponding hole effective masses of the KS and ST structures are different due to the different sign of the crystal-field splitting. The electron and hole effective masses of Se-based compounds are significantly smaller compared to the corresponding S-based compounds. They also decrease as the atomic number of the group IV elements (Si, Ge, Sn) increases, but the decrease is less notable than that caused by the substitution of S by Se.