Comparison of photoemission performance of AlGaN/GaN photocathodes with different GaN thickness

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In view of the different photoemission performance of AlGaN/GaN photocathode with different GaN thickness, three kinds of AlGaN/GaN photocathodes with different GaN layer. The GaN layer thickness of the AlGaN/GaN photocathodes is 7.5nm, 2nm and 0nm. The reflectivity and transmittance has tested, and got absortivity of them. The Cs/O activation results and quantum efficiency fitted results show that AlGaN/GaN photocathodes with a thick GaN layer can achieve higher photoemission and surface electron escape probability, and the quantum efficiency of them is 14.7%, 12.8% and 7.6% at 250nm. But the UV/solar rejection ratio is increasing along with the thickness of GaN decline.