Optical-Resonance-Enhanced Photoemission from Nanostructured GaAs Photocathodes

A negative electron affinity photocathode based on GaAs nanopillar-array (NPA) Mie-type resonators is demonstrated and significant quantum efficiency enhancement is observed. Nanophotonic resonance-assisted photoelectron emission into vacuum is investigated, indicating an enhanced density of optical states due to increased light concentration and increased electron emission area. For visible wavelengths, the Mie resonances in GaAs NPA reduce light reflectivity to less than 6% compared to a typical value >35% and result in maximum quantum efficiency 3.5 times greater than a GaAs wafer photocathode without the NPA structure. Comprehensive simulations and experimental studies are presented.