  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 dependence 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 Green's 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.
