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For the InxGa1-xAs photocathode with GaAs substrate, the range of the infrared spectrum response is extended with the In component increase, but the bandgap decreases, and the corresponding surface escape probability and the electron diffusion length will be greatly reduced. In order to overcome these difficulties, a method of dividing the emission layer into multi sublayers is proposed, namely, In component was gradually increased with the gradual increase of sublayer. Three types of reflective InGaAs/GaAs photocathodes with varied component emission layer were epitaxial grown by MOCVD, in which one sample is a thin emission layer InGaAs/GaAs photocathode, and the other two samples are the conventional thickness emission layer InGaAs/GaAs photocathodes and their emission layers are divided into three 0.6μm thickness sublayers and a 0.04 μm thickness varied component layer is introduced between sublayers in one of them, aims to form a gradual change structure between the sublayer interfaces. Then, the influences of different emission layer structures on the InGaAs/GaAs photocathode performance are investigated through comparing and analyzing the measured spectral response curves. Results show that the critical thickness of the surface epitaxial layer can be effectively improved by using the sublayer interface with varied component, and the test data after activation experiments indicate that the photocathode with multiple emission sublayers and varied component layer between them has the best spectral response, meanwhile, through fitting spectral response curves, we found the increase of its surface escape probability and electron diffusion length, which leads to the higher integral sensitivity and long-wave response.
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