A systematic study of polarized electron emission from strained   GaAs/GaAsP superlattice photocathodes
  Spin-polarized electron photoemission has been studied for GaAs/GaAs$_{1-x}$P$_x$ strained superlattice cathodes grown by gas-source molecular beam epitaxy. The superlattice structural parameters are systematically varied to optimize the photoemission characteristics. The heavy-hole and light-hole transitions are reproducibly observed in quantum efficiency spectra, enabling direct measurement of the band energies and the energy splitting. Electron-spin polarization as high as 86% with over 1% quantum efficiency has been observed. 
T. Maruyama, D.-A. Luh, A. Brachmann, J. E. Clendenin, E. L. Garwin,   S. Harvey, J. Jiang, R. E. Kirby, C. Y. Prescott, R. ...