Atomic hydrogen cleaning of polarized GaAs photocathodes

Abstract

Atomic hydrogen cleaning followed by heat cleaning at 450 °C was used to prepare negative-electron-affinity GaAs photocathodes. When hydrogen ions were eliminated, quantum efficiencies of 15% were obtained for bulk GaAs cathodes, higher than the results obtained using conventional 600 °C heat cleaning. The low-temperature cleaning technique was applied to thin strained GaAs cathodes used for producing highly polarized electrons. No depolarization was observed even when the optimum cleaning time of about 30 s was extended by a factor of 100.