Polarized Electron Emission from Strained GaAs/GaAsP Superlattice Photocathodes

Spin-polarized electron photoemission has been studied for GaAs/GaAs_1-xP_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.