【作者】 赵静；

【导师】 常本康； 郭晖；

【作者基本信息】 南京理工大学 ， 光学工程， 2013， 博士

【摘要】 本文围绕透射式GaAs光电阴极光学与光电发射性能的理论研究、结构设计与性能测试的软件研制、MBE生长阴极的实验评估、MOCVD生长的具有不同性能阴极的结构设计及实验等方面展开研究。针对透射式GaAs光电阴极光学性能研究的缺乏,根据薄膜光学矩阵理论,推导了包括玻璃基底、Si3N4增透层、Ga1-xAlxAs窗口层和GaAs发射层的透射式GaAs光电阴极光学性能计算公式,分析了除玻璃外三层材料的折射率、消光系数、厚度对光学性能曲线的影响。另外,对透射式GaAs光电阴极量子效率公式进行了光学性能的修正,同时分析了表征光学性能的吸收率与表征光电发射性能的量子效率之间的关系,研究了光学性能对光电发射性能的影响。根据透射式GaAs光电阴极光学与光电发射性能的理论计算,研制了透射式光电阴极结构设计软件,通过输入特定的设计要求参数,由软件自动计算后给出宽光谱响应或窄带响应材料结构设计结果及理论计算曲线。根据光学与光电发射性能的关系分析,研制了用于测试透射式光电阴极光学与光电发射性能的软件,通过输入波长、结构、实验光谱等,由软件自动拟合后得到阴极相关性能参数结果,实现了透射式光电阴极性能的自动测试,并提供了一种组件厚度的非接触测量手段。利用性能测试软件拟合了多种结构的MBE生长透射式GaAs光电阴极的实验反射率和透射率曲线,获得了阴极组件各个薄膜层的可靠厚度结果,提出了在MBE生长阴极的窗口层和发射层间存在一个低Al组分的过渡层。采用由光学性能修正的量子效率公式拟合了MBE生长透射式GaAs光电阴极的实验量子效率曲线,评估了多种掺杂结构的阴极光电发射性能,说明了MBE生长透射式GaAs光电阴极短波响应差、光谱特性不佳,因此结构设计有待改善。通过有效拟合美国ITT公司高性能GaAs光电阴极的实验量子效率,获得了高性能GaAs光电阴极的结构参数范围,其结果可用于指导国产GaAs光电阴极的材料设计和阴极制备。鉴于MBE生长阴极短波响应低、光谱特性差的问题,设计了宽光谱普通透射式GaAs光电阴极、蓝延伸透射式GaAs光电阴极、窄带透射式GaAlAs光电阴极,给出了满足设计要求的组件结构、Al组分、厚度、掺杂结构等。采用MOCVD生长了理论设计的三类阴极,测试了光学性能和光谱响应曲线,拟合了实验曲线并获得了性能参数。结果表明,MOCVD生长的宽光谱透射式GaAs光电阴极获得了比MBE生长阴极更好的性能。蓝延伸GaAs光电阴极积分灵敏度最高达到了1980μA/lm,窄带GaAlAs光电阴极实现了在532nm处达到峰值响应的要求,普通GaAs光电阴极的积分灵敏度最高达到了2320μA/lm,这与美国ITT公司当前对外公布的最高水平一致。更多还原

【Abstract】 The researches on the optical property and photoemission performance theories of the transmission-mode GaAs photocathodes, structural design and performance test softwares, performance evaluation of the MBE-grown photocathodes, and structural design and experiments of the MOCVD-grown photocathodes with different response properties were carried out in this thesis.Considering the lack of researches on the optical property, the calculation formula of optical property for the transmission-mode GaAs photocathode was derived based on thin film optical theory, where the photocathode module consisted of the glass substrate, the Si3N4antireflection layer, the Ga1-xAlxAs window layer and the GaAs active layer. The influences on the optical property curves corresponding to different thicknesses, refractive indexes and extinction coefficients were analyzed excluding the glass substrate. Besides, the quantum efficiency formula was deduced by taking into account the optical property. Following that, the relation between the absorptivity for optical property and the quantum efficiency for photoemission performance was discussed. Furthermore, the influence of optical property on the photoemission performance was investigated.The software on the structural design of the transmission-mode photocathode was developed on the basis of the theoretical calculation of the optical and photoemission performance. After entering the characteristic parameters of the wideband or narrowband response photocathodes, the structural result and the theoretical curves could be obtained by the software auto-calculation. The software on testing the optical and photoemission performance of the photocathodes was developed on the basis of the relationship between the optical property and photoemission performance. By means of inputting wavelength, structure parameters, experimental curves etc, the relating performance parameters could be computed by the software, which consequently realizes the automatic performance measurement for the transmission-mode photocathodes and affords a non-contact thickness measurement method.With the application of the performance measurement software, the experimental reflectivity and transmittance curves of transmission-mode GaAs photocathodes in varied structures grown by MBE were well fitted, and the thickness of each thin film in the cathode module was obtained, which reveals that a transition layer with the low Al component was presented between the window layer and the active layer for the MBE-grown GaAs photocathode. The experimental quantum efficiency curves were fitted by the formula modified with the optical property, and the photoemission performance of the various photocathodes were evaluated, which illustrates that the structure of the MBE-grown GaAs photocathode should be revised due to the low shortwave response and the poor spectral characteristic parameters. In addition, the experimental quantum efficiency curve of the high performance GaAs photocathode from American ITT Company was effectively fitted in order to gain the optimal structure ranges. The result can be used to guide the material design and cathode preparation of the domestic GaAs photocathodes.In view of the low shortwave response and the poor spectral characteristic of the MBE-grown photocathode, a wideband response standard GaAs, an extended blue GaAs and a narrowband response GaAlAs photocathodes were designed. Three kinds of transmission-mode module structures, Al components, thicknesses and doping distributions were calculated separately according to the required wideband or narrowband spectral response. The three designed photocathodes were grown by MOCVD, and their measured optical properties and spectral response curves were fitted by use of the performance measurement software. It is found that the MOCVD-grown wideband response GaAs photocathodes obtain better performance parameters than the MBE-grown ones. The highest integral sensitivity of the extended blue GaAs photocathode achieves1980μA/lm, meanwhile the narrowband response GaAlAs photocathode realizes the highest spectral response at the expected wavelength of532nm. The highest integral sensitivity of the standard GaAs photocathode achieves2320μA/lm, which is in accord with the released sensitivity level of American ITT Company.更多还原