High-Performance Spin-Polarized Photocathodes Using a GaAs/GaAsP Strain-Compensated Superlattice

Optimized transmission-type photocathodes with a GaAs/GaAsP strain-compensated superlattice were developed. The strain-compensated superlattice structures were of high crystal quality, and electron beams from the photocathodes had a maximum spin polarization of 92% and a quantum efficiency of 0.4% without an antireflection coating. The strain-compensated superlattice structure effectively prevented strain relaxation, and the high spin polarization was maintained up to a superlattice layer thickness of 300 nm. Increasing the superlattice layer thickness effectively improved the quantum efficiency while keeping the super high-brightness.