FACE DEPENDENCE OF THE SPIN POLARIZATION OF PHOTO-ELECTRONS FROM NEA GAAS (100) AND (110)

We present measurements of the spin polarization P of photoelectrons from negative electron affinity (NEA) GaAs (100) and find P=43% at a photon energy of 1.57 eV. This contrasts with a maximum P=21% measured by Erbudak and Reihl for NEA GaAs (110), which led them to conclude that NEA and high P exclude each other. This difference in P is important for sources of polarized electrons employing photoemission from GaAs. We suggest that the origin of this difference may be connected with differences in the photoelectron emission process at the two faces, as calculated by Burt and Inkson.