A POLAMZED PHOTOLm~ESCENCE ST~Y OF STRA~ED LAYER GAs PHOTOCATHODES*

  • Robin Alexander Mair
  • Published 1996

Abstract

Photoluminescence measurements have been madeon a set ofepitaxially grown strained GaAs photocathodes structures. The photocathodes are designed to exhibit a strain-induced enhancement of the electron spin polarization obtainable by optical pumping with circularly polarized radiation of near band gap energy. For the case of non-strained GaAs, the degree of spin polarization is limited to 50% by crystal symmetry. Under an appropriate uniaxial compression or tension, however, the valence band structure near the gap minimum is modified such that a spin polarization of 100% is theoretically possible. A total of nine samples with biaxial compressive strains ranging from zero to ~0.8% are studied. X-ray diffraction analysis, utilizing Bragg reflections, is used to . determine the crystal lattice structure of the samples. Luminescence spectra and luminescence circular polarization data are obtained at room temperature, %78 K and w 12 K. The degree of luminescence circular polarization is used as a relative measure of the photo-excited electron spin polarization. The room temperature luminesce~ce circular polarization data is compared with spin polarization when the samples are used as electron negative electron affinity surface preparation. the measured electron photmemitters with a The luminescence data is also analyzed in conjunction with the crystal structure data with the goal of understanding the strain dependent valence band structure, optical pumping characteristics tocathode structures. A simple obtained for the seti of samples. and spin depolarization mechanisms of the ph~ model is used to describe the luminescence data Within the assumptions of the model, the defor-

Cite this paper

@inproceedings{Mair1996APP, title={A POLAMZED PHOTOLm~ESCENCE ST~Y OF STRA~ED LAYER GAs PHOTOCATHODES*}, author={Robin Alexander Mair}, year={1996} }