We review the progress achieved in our laboratory towards the further development of a non‐magnetic, solid state polarized electron source. Alloys of Al xGa1−xAs grown by molecular beam‐epitaxy are shown to allow room temperature operation and generate polarized electrons by optical pumping at convenient wavelengths with polarization values in the range P=45%±1%. The performance of multilayers of GaAs−AlxGa1−xAs as photoemitters is also briefly described. Surface passivation of Al xGa1−xAs epitaxial layers is shown to be an efficient way for protecting the cathodes during exposure to atmosphere and allowing subsequent regeneration of the source parameters after ultrahighvacuum annealing. Ideas for further increasing the spin polarization P beyond the theoretical limit of 50%, valid for GaAs, are also discussed.