Improved Electron Yield and Spin-Polarization from III-V Photocathodes via Bias Enhanced Carrier Drift

72323B03-I The exploration of certain regimes of high energy physics will require the development of photocathodes with emitted electron spin-polarizations above 90%. Emitted electron spin-polarizations approaching 90% have been achieved, but at the expense of quantum yield. Because natural diffusion spatial spread disfavors complete transport to the emitting surface, this project will develop technology for adding a drift component to the photoexcited electron diffusion velocity, thereby reducing electron residence time after excitation. This bias also should enhance overall emission probability by modifying the natural diffusion momentum with a drift component. Phase I will design and develop a bias-capable cathode holder, and test the electron emission characteristics, in order to verify that the bias-enhanced GaAs photocathode results in a well-modified quantum yield. Commercial Applications and Other Benefits as described by awardee: All laboratories utilizing GaAs-based emitters could take advantage of this technology as it will be a ready replacement for existing photoemitters. The final product also should find use in electron sources utilized in electron microscopes and other analytical tools for studying surface, atomic, and molecular physics, etc.