Attenuation performance of reflection-mode AlGaN photocathode under different preparation methods.

To research the attenuation performance of the AlGaN photocathode, three samples with the same structures grown by metalorganic chemical vapor deposition were activated with three different activation methods, which are called Cs-only, Cs-O, and Cs-O-Cs activation, respectively. The spectral responses and attenuated photocurrents of the three AlGaN photocathodes were measured. The results show that the Cs-O activated AlGaN photocathode exhibits the lowest attenuation speed in the first few hours, and the attenuation speed of the Cs-only activated one is fastest. After attenuating for 90 min, the attenuation photocurrent curve of the Cs-O-Cs activated sample is coincident with that of the Cs-O activated one. The main factor affecting the photocurrent attenuation is related to Cs atoms desorbed from the photocathode surface.