Resolution properties of varied doping and varied composition reflection-mode Al<sub>x</sub>Ga<sub>1-x</sub>As/GaAs photocathodes

According to the established resolution model and modulation transfer function(MTF) of varied doping and varied composition reflection-mode Al_xGa_1-xAs/GaAs photocathode, the resolutions of four types reflection-mode(r-mode) photocathodes: linearly varied doping and linearly varied Al composition, uniform doping and linearly varied Al composition, linearly varied doping and uniform Al composition, uniform doping and uniform Al composition structures were simulated, and the effects of Al composition, the types of doping, Al_xGa_1-xAs layer thickness, GaAs layer thickness, and incident light wavelength on the resolution of cathodes were analyzed. The simulation results indicate that the changed doping and changed band-gap structures can also upgraded the resolution for r-mode Al_xGa_1-xAs /GaAs photocathodes, and the effect of linearly doping and linearly composition structure is more pronounced. The simulation results also show that The MTFs of the cathodes with the Al composition from 0.45 to 0 linearly declining are highest. The MTFs of the cathodes with the linearly doping from 1×10¹⁹cm^-3 to 1×10¹⁸ cm^-3are higher that with uniform 1×10¹⁹cm^-3 doping. With the increase of Al_xGa_1-xAs thickness, GaAs thickness and incident light wavelength, the MTFs of four types photocathode have different regularity.