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To theoretically research the influence of a varied Al component on the active layer of AlGaN photocathodes,the first principle based on density functional theory is used to calculate the formation energy and band structure of AlxGa1-xN with x at 0,0.125,0.25,0.325,and 0.5.The calculation results show that the formation energy declines along with the Al component rise,while the band gap is increasing with Al component increasing.AlxGa1-xN with x at 0,0.125,0.25,0.325,and 0.5 are direct band gap semiconductors,and their absorption coefficient curves have the same variation tendency.For further study,we designed two kinds of reflection-mode AlGaN photocathode samples.Sample 1 has an AlxGa1-xN active layer with varied A1 component ranging from 0.5 to 0 and decreasing from the bulk to the surface,while sample 2 has an AlxGa1-xN active layer with the fixed A1 component of 0.25.Using the multi-information measurement system,we measured the spectral response of the activated samples at room temperature.Their photocathode parameters were obtained by fitting quantum efficiency curves.Results show that sample 1 has a better spectral response than sample 2 at the range of short-wavelength.This work provides a reference for the structure design of the AlGaN photocathode.