Enhanced photoemission performance of an AlGaN photocathode by a superlattice emission layer

Abstract

The AlGaN photocathode with a superlattice emission layer was grown by metal organic chemical vapor deposition. The existence of the superlattice structure was confirmed using a transmission electron microscope, and its optical and electrical properties were measured. The results showed that the introduction of a superlattice emission layer can reduce the transmittance and reflectance at 275 nm and improve the absorption of incident light. In particular, the Hall measurement results indicate that the introduction of a superlattice structure can significantly increase the concentration of holes in the AlGaN photocathode material. The activation experiment demonstrated that the photocurrent of the AlGaN photocathode subassembly with a superlattice structure increased significantly after Cs/O activation and that it showed better photoemission performance. The increase in the incident light absorption to produce more photoelectrons, the enhancement of photoelectron transport capacity by the polarized electric field generated by the superlattice structure, and the reduction in the surface barrier caused by the higher hole concentration were responsible for the significant improvement in photoemission performance.