Quaternary semiconductors with positive crystal field splitting: Potential high-efficiency spin-polarized electron sources

Traditional high efficiency spin-polarized electron sources (SPES) consist mainly of binary or pseudobinary zinc-blende GaAs based materials, whereas their ternary analogs $II-IV-V2$ (⁠$II=Zn$⁠, Cd, $IV=Si$⁠, Ge, Sn, and $V=As$⁠) as well as II-VI ternary analogs $I-III-VI2$ (⁠$I=Cu$⁠, Ag, $III=Al$⁠, Ga, In, and $VI=Se$⁠) have not drawn wide attention because their crystal field splitting $ΔCF$ near the valence band maximum is either negative or close to zero in their ground state chalcopyrite structure. Using first-principles calculations, we show that some derivative quaternary $I-III-II2-VI4$ and $II-IV-III2-V4$ compounds can have coherent ground state stannite or kesterite structures with large and positive $ΔCF$ due to their increased chemical and structural flexibility. We propose that $ZnSiAl2As4$ and $CdGeAl2As4$ in the stannite structure, and $ZnSnGa2As4$ and $CuAlCd2Se4$ in the kesterite structure could be good candidate SPES materials with high polarization and quantum efficiency.