INVESTIGATION IMPROVEMENT ACTIVATION OF GaN NEGATIVE ELECTRON AFFINITY PHOTO-CATHODES

Two to five micrometer thick P-AlxGa1-xN/GaN layers with 0＜X≤0.4 were grown by low-pressure metal organic chemical Vapour deposition on sapphire（0001）substrates.For Al concentrations 0.2＜X＜0.7 in the AlxGa1-xN layers,The assessment of P-type GaN active layers Shows electron diffusion Lengths of 2 to 5 μm for a doping level of 3×10¹⁹cm^-3。strcure model of energy bands for surface GaN-based phtocathode was and the result of experiment was satisfied with the model.