University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico
Arizona State University, Tempe, USA
BNL, Upton, New York, USA
The experimental investigation of new photocathode ma- terials is time-consuming, expensive, and difficult to accom- plish. Computational modelling offers fast and inexpensive ways to explore new materials, and operating conditions, that could potentially enhance the efficiency of polarized electron beam photocathodes. We report on Monte-Carlo simulation of electron spin polarization (ESP) and quantum efficiency (QE) of bulk GaAs at 2, 77, and 300 K using the data obtained from Density Functional Theory (DFT) cal- culations at the corresponding temperatures. The simulated results of ESP and QE were compared with reported exper- imental measurements, and showed good agreement at 77 and 300 K.
BNL, Upton, New York, USA
Sandia National Laboratories, Albuquerque, New Mexico, USA
Electron sources producing highly spin-polarized electron beams are currently possible only with photocathodes based on GaAs and other III-V semiconductors. GaAs/GaAsP superlattice (SL) photocathodes with a distributed Bragg reflector (DBR) represent the state of the art for the production of spin-polarized electrons. We present results on a SL-DBR GaAs/GaAsP structure designed to leverage strain compensation to achieve simultaneously high QE and spin polarization. These photocathode structures were grown using molecular beam epitaxy and achieved quantum efficiencies exceeding 15% and electron spin polarization of about 75% when illuminated with near bandgap photon energies.
