SPIN-POLARIZED PHOTOEMISSION FROM THIN GAAS PHOTOCATHODES

The spin polarization of electrons photoemitted from negative electron affinity (NEA) thin GaAs photocathodes has been measured by means of Mott scattering. Thin epitaxial layers have been grown on different su bstrates with either small or large lattice mis-match. In this last ca se the layer results considerably strained allowing the emission of hi ghly (more than 50%) polarized electrons. The effect of the strain rel axation due to sample annealing on the beam polarization is also discu ssed.