Quantum efficiency of heterostructured AlN/AlxGa1−xN photocathodes with graded bandgap emission layer
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A heterostructured AlN/AlxGa1−xN photocathode consisting of a sapphire substrate layer, a AlN buffer layer, and a graded bandgap emission layer is proposed to improve the quantum efficiency of AlGaN photocathode. The theoretical models for transmission-mode and reflection-mode photocathodes were deduced based on one-dimensional continuity equations to analyze the characteristics of the devices. Results show that the multilevel built-in electric field induced by the bandgap gradation in the emission layer can improve the quantum efficiency because of the longer electron diffusion length and the reduction of the back-interface recombination losses. The effect of thicknesses of photocathodes and Al composition in the sublayers on efficiency is discussed. This work would provide theoretical guidance for better performance of AlGaN photocathodes.
This work is financed by the National Natural Science Foundation of China (Grant No. 61705108), the Natural Science Foundation of Jiangsu Province (Grant No. BK20170959), and the startup foundation for introducing talent of NUIST (Grant No. 2016r039). It is also financed by the National Natural Science Foundation of China (Grant Nos. 61704075 and 61601198).
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