Operation of III-V Semiconductor Photocathodes in the Semitransparent Mode

Abstract

Calculations show that very nearly bulk quality material is required for high-efficiency semitransparent III-V photocathodes. For narrow-band response, this can be obtained by epitaxially growing a thin layer of a semiconductor whose bandgap is slightly less than that of the substrate. Cathodes made by growing GaAsSb on GaAs have given quantum efficiencies comparable with front surface values, peaking out at 0.54% at 1.35 eV near the onset of absorption in the GaAs substrate. Preliminary results demonstrating semitransparent yield at 1.06 μ of 0.013% are also shown.