Fig. 1. Structure of GaAs-based photocathode samples

Fig. 2. Cross-sectional SEM images

Fig. 3. Reflectivity curves of GaAs-based photocathode samples

Fig. 4. Measured quantum efficiency curves of GaAs cathode samples after Cs/O activation

Fig. 5. Structure of complicated multi-layer GaAs-based photocathodes

Fig. 6. Optical properties and quantum efficiency curves with changing thicknesses of GaAs emission layer in multi-layer GaAs-based photocathodes

Fig. 7. Optical properties and quantum efficiency curves with changing thicknesses of Al_xGa_1-xAs buffer layer in multi-layer GaAs-based photocathodes

Fig. 8. Optical properties and quantum efficiency curves with changing Al proportions in multi-layer GaAs-based photocathodes

Fig. 9. Fitted curves of quantum efficiency