Photoemission performance of thin graded structure AlGaN photocathode.

In order to research a high-efficiency AlGaN photocathode, the AlGaN photocathodes with varied Al composition (0.68 and 0.4) and uniform Al composition (0.24) were grown. The photocathodes were activated by Cs adsorption and received their spectral response via multi-information system. Results show that the absorption rate of the AlGaN photocathode with varied Al composition is half of the AlGaN photocathode with uniform Al composition, but the quantum efficiency of the photocathode with varied Al composition is approximately 29% higher than that of the photocathode with uniform Al composition. The built-in field within the emission layer of the AlGaN photocathode with varied Al composition is much higher than that of the photocathode with uniform Al composition, which is the main factor that promotes the photoelectron movement toward the photocathode surface and improves photoemission performance of the AlGaN photocathode.