Enhancement of near-infrared response of InGaAs photocathode through interaction of 1064 nm light with activated surface

Abstract

To enhance the near-infrared response of InGaAs photocathodes, we proposed an improved activation recipe, including conventional Cs/O or Cs/NF3 activation with white light and a subsequent re-activation with 1064 nm light. In-situ activation, re-activation and characterization were performed to investigate the relationship between the spectral response and the emitting surface. Multiple activation experiments demonstrated that re-activation illuminated by the 1064 nm light after conventional Cs/O activation effectively enhanced the spectral response in the near-infrared range, e.g., by a factor of 2–6 at 1064 nm, and this recipe had no enhancement effect on the spectral response of the Cs/NF3 activated samples. After Cs/O activation, the surface barrier of the activation surface was further optimized through the interaction of the 1064 nm light with the activated surface during re-activation. The minor optimization of the surface barrier could significantly improve the tunneling probability of the electrons excited by the near-infrared light. Moreover, the 1064 nm near-infrared light in re-activation could not be replaced by ultraviolet-blue light, as the interaction of ultraviolet-blue light with the activated surface had minimal effect on the surface barrier.