Systematic Study of Polarized Electron Emission from Strained GaAs/GaAsP Superlattice Photocathodes.

Maruyama, T. ; Luh, D. A. ; Brachmann, A.

Technical Information Center Oak Ridge Tennessee

关键词: Photoemission;    Electron beams;    Photocathodes;    Superlattices;    Spin;   

RP-ID  :  DE2004826745

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

Polarized electrons have been essential for high-energy parity-violating experiments and measurements of nucleon spin structure, and polarized electron beams will be required for all future linear colliders. Polarized electrons are readily produced by GaAs photocathode sources. When a circularly polarized laser beam tuned to the bandgap minimum is directed to the negative-electron-affinity (NEA) surface of a GaAs crystal, longitudinally polarized electrons are emitted into vacuum. The electron polarization is easily reversed by reversing the laser polarization. The theoretical maximum polarization of 50% for natural GaAs was first exceeded in 1991 using the lattice mismatch of a thin InGaAs layer epitaxially grown over a GaAs substrate to generate a strain in the former that broke the natural degeneracy between the heavy- and light-hole valence bands.