| High-speed framing cameras are one of the most important research tools of an physicalultrafast process, they have broad application in nuclear fusion, plasma physics with hightemperature and high density, nonlinear optics, photobiology and so on. With high quantumefficiency, low dark current, low energy distribution and low emittance, GaAs negative electronaffinity (NEA) photocathodes have the wide application in photomultipliers (PMT), laserdetection, radiation measurement, automatic control, low-light level image, spintronics andelectron-beam lithography. Because of these outstanding characteristics, it is possible that theGaAs NEA cathodes can be used in high-speed framing cameras if these NEA semiconductorphotocathodes have high-speed response behavior.In this paper, In theory, we design a new GaAs NEA cathode structure with ultrafast responseand theoretically analyse its response characteristics for improving the response speed; Inexperiment, based on the third generation image intensifier, this paper completes the wholetechnical processes of the third generation image intensifier uesd by double microstrip line GaAscathode gated framing camera.Firstly, we describe the characteristics of GaAs photocathodes and the manufacturingprocesses of the framing tube. The high-speed framing cameras are briefly described. Forimproving the further development of framing cameras, we bring forward the plan of combiningGaAs photocathodes with the application of the high-speed framing cameras.Secondly, a large exponential-doping transmission-mode GaAs photocathode is designed toimprove the response speed of GaAs NEA photocathodes to meet the application demands offraming cameras. The characteristics of the new photocathode——the quantum efficiency,spatial time resolution, is discussed in detail. Its response time is shorted to less than10ps, theaverage quantum efficiency can reach10-15%; a new concept——the average decay timeconstant is introduced firstly to the simulation and the defects in the previous calculation iseffectively eliminated. The results provide necessarily theoretical support for the application ofsemiconductor NEA cathodes to the picosecond framing cameras.Thirdly, the high resolution X ray diffraction technology is introduced briefly. we design andgrow the GaAs/GaAlAs epitaxial wafer for the GaAs photocathode fabrication. The diffraction curves are measured by the high resolution X-ray diffractometer. The structure characteristics oftrain Al component content and the stress is analyzed by the asymmetric diffraction measurementtechnique. The analysis results show that the GaAs/GaAlAs structure has good uniformitydistribution about Al component content and the stress. The strain curvature radius distribution ofthe epitaxial wafer obtained the high angle diffraction measurements is better than that of the lowangle diffraction measurements, which may indicate that the high angle diffraction can moremacroscopically reflect the structural stress condition.Fourth, the works as follows are made: the vacuum deposition, grid electrode fabrication byphotolithography, GaAs substrate corrosion; the new thermal bonding technique in vacuum ofstrip-type GaAs and K4glass is explored, in which Ni-Cr grid electrode instead by the auxiliarybonding material Si3N4; the positioning device is designed and fabricated for strip-type GaAs andK4glass positioning accurately in the vacuum heat bonding process.Finally, the vacuum diode is fabricated by the processes of the Cs: O activation of GaAsphotocathodes and the Indium seal experiment. Then, the whole technological processes of thenew framing camera are finished, which provide the necessarily experimental support.This thesis exploringly studies the fabrication processes of GaAs photocathode gated framingcamera, and study the ultrafast theory of the NEA photocathode. This work provides necessarilytheoretical and technological support, such as multi-channel framing camera and the developmentother ultrafast field. |
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