QUANTUM-EFFICIENCY DEPENDENCE OF THE SPIN POLARIZATION OF PHOTOEMISSION FROM A GAAS-ALGAAS SUPERLATTICE

We measured the quantum-efficiency (QE) dependence of the spin polariz ation of photoemission from a GaAs-AlGaAs superlattice over a wide ran ge of QE values. In the QE range from 10(-4) to 10(-9), a change in th e polarization from 76% to 48% was observed at a wavelength of 778.5 n m. The maximum polarization at 778.5 nm was observed at a QE one tenth of the maximum value. We also observed a similar dependence at other wavelengths. Such a behavior suggests that the vacuum level and surfac e potential barrier play important roles concerning the spin polarizat ion of photoemission.