Polarization Possibilities of Small Spin-Orbit Interaction in Strained-Superlattice Photocathodes

关键词: GALLIUM ARSENIDES;    GALLIUM PHOSPHIDES;    ARSENIC COMPOUNDS;    PHOSPHIDES;    L-S COUPLING;    PERFORMANCE;    PHOTOCATHODES;    POLARIZATION;    QUANTUM EFFICIENCY;    RELAXATION;    SUPERLATTICES;    LINEAR COLLIDERS;    S CODES;    ELECTRO;   

DOI  :  10.2172/992984
RP-ID  :  SLAC-PUB-14128
PID  :  OSTI ID: 992984
Others  :  TRN: US1008024

美国|英语

来源: SciTech Connect

【 摘 要 】

Strained-superlattice photocathodes based on InGaP/GaAs were investigated. The photocathode performance is found highly dependent on the superlattice parameters. The electron confinement energy in superlattice appears important. The strained-superlattice structure based on GaAsP/GaAs, with a maximum polarization as high as 90% and more than 1% quantum efficiency, is presently the prime candidate for the ILC polarized electron photocathodes. A recent systematic study shows, however, that the peak polarization seems saturated even though the heavy-hole (HH) and light-hole (LH) band splitting is increased significantly, indicating that there is a material specific spin relaxation mechanism. It is widely accepted that the D'yakonov-Perel mechanism is the dominant spin relaxation mechanism in the III-V compound superlattice structures with a low p-doping ({le} 10{sup 17} cm{sup -3}), and that the spin relaxation may be reduced by choosing a material with a smaller spin-orbit interaction. As the spin-orbit interaction in phosphides is much smaller than in arsenides, strained-superlattice structure based on InGaP/GaAs were investigated. The computer code SPECCODE developed by Subashiev and Gerchikov has been used for calculating the band structures in superlattice.