We show that periodically doped, flat surfaces can act as reflective diffraction gratings for atomic and molecular matter waves. The diffraction element is realized by exploiting that charged dopants locally suppress quantum reflection from the Casim
ir-Polder potential. We present a general quantum scattering theory for reflection off periodically charged surfaces and discuss the requirements for the observation of multiple diffraction peaks.
The electronic structure of bulk fcc GaAs, fcc and tetragonal CrAs, and CrAs/GaAs supercells, computed within LMTO local spin-density functional theory, is used to extract the band alignment (band offset) for the [1,0,0] GaAs/CrAs interface in depend
ence of the spin orientation. With the lateral lattice constant fixed to the experimental bulk GaAs value, a local energy minimum is found for a tetragonal CrAs unit cell with a slightly ($approx$ 2%) reduced longitudinal ([1,0,0]) lattice constant. Due to the identified spin-dependent band alignment, half-metallicity of CrAs no longer is a key requirement for spin-filtering. Encouraged by these findings, we study the spin-dependent tunneling current in [1,0,0] GaAs/CrAs/GaAs heterostructures within the non-equilibrium Greens function approach for an effective tight-binding Hamiltonian derived from the LMTO electronic structure. Results indicate that these heterostructures are probable candidates for efficient room-temperature all-semiconductor spin-filtering devices.
