Double-step excitation in spin polarized photoemission from NEA GaAs(100)

• Published in: Solid state communications Vol. 58; no. 11; pp. 775 - 779
• Main Authors: Luig, T., Rissmann, M., Merz, H.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.1986; Elsevier
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Photoemission and photoelectron spectra; Physics; Potential barrier; Oxygen; Semiconductor materials; Circular polarization; Electron affinity; Photocathode; Cesium; Polarized light; Inorganic compound; Gallium Arsenides; Polarized spin; Activator; Photoelectron emission; Surface potential
• ISSN: 0038-1098; 1879-2766
• DOI: 10.1016/0038-1098(86)90766-0

Spin polarized photoelectrons emitted from a NEA GaAs(100)-photocathode, which is activated in a special way with oxygen and cesium, can have a broad energy distribution with a maximum energy higher than expected for an one-photon excitation process within the bulk from the valence band edge into the conduction band. Also the shape of the energy distribution curves of the emitted electrons depends on the intensity of the incident light. This double-step excitation process is observed for aged and/or oxidized activation layers, especially for surfaces with a strongly developed, negative electron affinity. To give an explanation of these effects, it is suggested that excited conduction electrons absorb a further photon within the band bending region. This second photoemission excitation step seems to be enhanced by an interfacial barrier between the band bending region and the cesium-oxygen activation layer as well as by the existence of two-dimensional surface subbands.