The capability comparison of high-performance GaAs photocathodes

High-performance reflection-mode GaAs photocathode (named cathode 1 for short) with the integral sensitivity of 2140μA/lm is prepared by adopting "high-low temperature" two-step activation and using heavily p-type Be-doped GaAs materials, which is grown by molecular beam epitaxy (MBE) technique. Moreover, spectral response characteristic and cathodes performance parameters of two cathodes are obtained by spectral response database we compiled, one is the reflection-mode photocathode (named cathode 2 for short) with the integral sensitivity of 1800μA/lm reported by G. H. Olsen in the 70s; the other is the transmission-mode photocathode (named cathode 3 for short) with the integral sensitivity 3070μA/lm reported by O. H. W. Siegmund in 2003. A transmission-mode cathode (named cathode 4 for short) is acquired by computer simulation on the basis of cathode 1, and its integral sensitivity is 1907μA/lm, then we compare the reflection-mode cathodes (cathode 1 and cathode 2) and the transmission-mode cathodes (cathode 3 and cathode 4), respectively, and analyze the cause for performance difference among these cathodes, the results show that the surface escape probability of cathode 1 reach to 0.62, which is lower slightly that of cathode 2, so preparation technique of cathode 1 has gotten higher the surface escape probability, but the electron diffusion length of cathode 1 and the back interface recombination velocity of cathode 4 is not better compared to cathode 2 or cathode 3. Which shows preparation technique of cathode 1 obtains better surface barrier, it need to be optimized all the same for achieving higher performance GaAs photocathodes.