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-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 Delta(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 Delta(CF) due to their increased chemical and structural flexibility. We propose that ZnSiAl(2)As(4) and CdGeAl(2)As(4) in the stannite structure, and ZnSnGa(2)As(4) and CuAlCd(2)Se(4) in the kesterite structure could be good candidate SPES materials with high polarization and quantum efficiency.