Study of RE-Doped InGaN Semiconductor Heterostructures for Photocathodes*

Photocathodes, devices that emit electrons when illuminated, are vital for generating high-brightness and spin-polarized electron beams in accelerator physics. Indium gallium nitride (InGaN) heterostructures are promising next-generation photocathode materials due to their tunable bandgap, high quantum efficiency, and chemical robustness under extreme conditions. However, structural defects such as point defects and dislocations introduce electronic states in the bandgap that degrade emission efficiency and carrier transport. This project surveys current literature on InGaN-based photocathodes, focusing on the role of rare-earth (RE) doping and defect control. Using advanced characterization techniques, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-VIS spectroscopy, Raman, FTIR, and Hall effect measurements, we assess how defects impact band structure, optical behavior, and electrical performance. These insights guide the design of RE-doped InGaN heterostructures optimized for durable, high-performance photocathodes in accelerator systems.