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

摘要

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-Ⅴ_2 (Ⅱ=Zn, Cd, Ⅳ=Si, Ge, Sn, and Ⅴ = As) as well as Ⅱ-Ⅵ ternary analogs Ⅰ-Ⅲ-Ⅵ_2 (Ⅰ = Cu, Ag, Ⅲ=Al, Ga, In, and Ⅵ=Se) have not drawn wide attention because their crystal field splitting △_(CF) 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-Ⅱ_2-Ⅵ_4 and Ⅱ-Ⅳ-Ⅲ_2-Ⅴ_4 compounds can have coherent ground state stannite or kesterite structures with large and positive △_(CF) due to their increased chemical and structural flexibility. We propose that ZnSiAl_2As_4 and CdGeAl_2As_4 in the stannite structure, and ZnSnGa_2As_4 and CuAlCd_2Se_4 in the kesterite structure could be good candidate SPES materials with high polarization and quantum efficiency.