Transmission-mode Varied-doping GaAs Photocathode And Application In Low-light-level Image Intensifier

In order to improve the technical level of domestic3rd low-light-level image intensifier, the systematic researches on the preparation and evaluation of transmission-mode varied-doping GaAs cathode material and module, optical performance of cathode module, automatic activation technology, tranmission-mode spectral response theory and application of the tranmission-mode varied-doping GaAs photocathode were carried out in this thesis.Eight transmission-mode varied-doping GaAs photocathode materials of different doping structures were grown by MBE and MOCVD. The cathode material structure was measured by electrochemical C-V, which validates the feasibility of achievement of the exponential-doping, gradient-doping and varied-composition structure. The cathode material quality was measured by X-ray diffraction, and the relationship between X-ray relative diffraction intensity and integral sensitivity of GaAlAs/GaAs photocathode was established, which proposed an evaluation methode for the crystal lattice integrality of GaAlAs/GaAs photocathode material.A theoretical mode using the thin film optical matrix for transmission-mode cathode module was set up, which analyzed the relationship between the the reflectance and transmittance curve of transmission-mdoe GaAs photocathode module and the film geometrical thickness. The reflectance and transmittance curves of transmission-mode exponential-doping cathode modules were tested by the spectrophotometer, and were well fitted by the programmed optical performance testing software which could reveal the respective film thickness value in the cathode module.A computer-automated system that could activate transmission-mode varied-doping GaAs photocathode was developed by redesigning the weak signal detection module, adopting the programmable current source regarding cesium source and oxygen source, and optimizing the activation process flow. This system realized the automatic activation of varied-doping GaAs photocathode, which avoided the manual mis-operation and greatly increased the photocathode activation efficiency and process repeatability. Development of the system laid a foundation for mass-production of high-performance varied-doping GaAs photocathode.By solving one-dimensional continuity equation, the quantum efficiency formula of transmission-mode GaAs photocathode was revised, which considers the shortwave cutoff and the optical performance. Using the formula, the domestic and foreign quantum efficiency curves of the transmission-mode GaAs photocathode were well fitted and the cathode performance parameters were obtained. Comparison of domestic and foreign GaAs cathode performance parameters shows that the electron diffusion length and surface electron escape probability of varied-doping GaAs photocathode is close to or above the foreign level, while the interface recombination rate is still higher than the foreign cathode, which leads to the backwardness of shortwave response for the domestic cathode.The sensitivity, resolution, equivalent background input and brightness gain of12low-light-level image intensifiers adopting transmission-mode varied-doping GaAs photocathode were measured, and the measured average sensitivity, average resolution, average equivalent background input and average brightness gain were1947μA/lm,49lp/mm,1.76x10-7lx, and11155.14, respectively. The spectral response monitoring test, impact test, vibration test and high-low temperature test of the image intensifier with varied-doping GaAs photocathode was carried out to assess the spectral sensitivity stability of the low-light-level image intensifier equipped with transmission-mode varied-doping GaAs photocathode. The results show that the the better stability of the varied-doping image intensifier than the uniform-doping one, whihch verifies the superiority in application of the transmission-mode varied-doping GaAs photocathode into image intensifier.