Highly-Polarized Electron Emission from Strain-Compensated Superlattices and Superlattices with High-Valence-Band Splitting

摘要

Strained layer heterostructure and short-period superlattice structures have been used to advantage in achieving highly spin-polarized electron photoemission. The strain-induced splitting of the valence band at the band-gap minimum provides a high electron polarization in the conduction band under excitation by circularly polarized light. Smearing of the interband absorption edge and the hole scattering processes lead to polarization in the band-edge absorption of less than 100%, polarization losses being typically about 6%. This mechanism sets a limit on the maximum polarization of emitted electrons. The initial polarization can be increased by choosing structures with a higher valence band splitting.