Study On Photoemission Characteristics Of Transmissive GaAlAs/GaAs Vacuum Devices

This paper focuses on systematic research on the quantum efficiency theoretical model,structure design and photoemission performance of the transmissive variable composition and variable doped GaAlAs/GaAs photocathode.Based on the"three-step model"of photoemission,the one-dimensional minority carrier diffusion equation is solved using boundary conditions,and the quantum efficiency theoretical model of the transmissive GaAlAs/GaAs photocathode is established.The influence of the change trend of Al composition,the thickness of each sublayer in the Ga Al As window layer and the thickness of the Ga As emission layer on the quantum efficiency of the photocathode is analyzed.Theoretical calculation results show that the Al composition change trend first rapidly decreases and then slowly decreases to improve the short-wave response of the cathode.The thicker the Ga As emission layer,the stronger the long-wave response of the cathode.The Ga Al As window layer mainly affects the short-wave response of the photocathode.The quantum efficiency theoretical model of photocathode has certain guiding significance for the structure design of GaAlAs/GaAs photocathode.MOCVD epitaxial growth technology is used to prepare variable composition and variable doped GaAlAs/GaAs photocathode film,and then through processes such as chemical etching,high temperature heating purification and Cs-O alternate activation,a negative electron affinity cathode assembly is obtained.Nickel-aluminum alloy material is selected as the anode component,the cathode component and the anode component adopt the vacuum close-fitting method,and the GaAlAs/GaAs cathode component and the nickel-aluminum alloy anode component are packaged into a vacuum device by the indium sealing process.The vacuum degree of the device is 5×10^-8Pa.A test system for spectral response and volt-ampere characteristics was built,and experimental tests on the volt-ampere characteristics of GaAlAs/GaAs optoelectronic devices under different incident light powers were carried out.The results show that the stronger the incident light power,the corresponding critical voltage increases with the incident light intensity.The linear becomes larger.Finally,the spectral response sensitivity of the transmissive GaAlAs/GaAs photoelectric conversion device was tested under different bias voltages.The results showed that the greater the bias voltage,the longer-wave response of the device was enhanced.The established quantum efficiency theoretical model is used to fit the electron escape probability under different bias voltages.The fitting results show that the greater the bias voltage,the greater the corresponding electron escape probability.The research work in this paper has certain guiding significance for the structural design of the photocathode and the selection of working conditions for the transmissive GaAlAs/GaAs vacuum devices.