Study on the sensitivity decrease of reflection-mode GaN NEA photocathode

The experiment result discloses that the sensitivity of the reflection-mode NEA GaN photocathodes decrease with time after activation. Through analyzing the experiment result, it is found that the changes of the element content in the surface of the cathodes play an important role in the decrease course of the sensitivity. In order to explain the above result, a surface model of the reflection-mode NEA GaN photocathodes is put forward. By using this model, the inner mechanism leading to this result is that the dipoles direction changes because the harmful gases are adsorbed in the surface of the photocathodes.