First-principles study on the effective masses of zinc-blend-derived Cu_2Zn-IV-VI_4 (IV = Sn, Ge, Si and VI = S, Se)

TL;DR

This study uses first-principles calculations to analyze the electron and hole effective masses in Cu_2Zn-IV-VI_4 semiconductors with different structures and compositions, revealing anisotropic hole masses and composition-dependent effective mass trends.

Contribution

It provides a systematic first-principles analysis of effective masses in Cu_2Zn-IV-VI_4 semiconductors, highlighting differences between structures and compositions.

Findings

Electron effective masses are nearly isotropic.

Hole effective masses show strong anisotropy.

Se-based compounds have smaller effective masses than S-based ones.

Abstract

The electron and hole effective masses of kesterite (KS) and stannite (ST) structured Cu_2Zn-IV-VI_4 (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 anisotropy is observed for the hole effective mass. 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.