The research of surface state and photoelectronic emission characteristic of NEA GaN photocathode

The GaN sample doped with Mg at a level of 1.6x410¹⁷ cm^-3 were grown through MOCVD on a sapphire substrate, The thick is 150nm, a buffer layer of AlN of 20 nm is grown. The opaque GaN sample is cleaned with physical and chemical treatment to remove large amount of contaminations The subsequent heating process of 710°C in the high-vacuum chamber makes the surface with the lowest content of oxygen and carbon. This step maintains about 20 minutes and until the temperature decrease to the room temperature naturally [1].