讨论了一种具有超快时问响应特性的新光电阴极，即大梯度指数掺杂透射式GaAs负电子亲和势（NEA）光电阴极，模拟了它的量子效率、时间分辨和空间分辨能力等特性．理论分析结果表明，由于大梯度指数掺杂设计方式，在吸收层内形成较大的内建电场，因此光生电子在GaAsNEA阴极内的渡越时间大大缩短，当GaAs吸收层厚度一0．9Ixm时，其响应时间达到-10ps，说明这种新NEA阴极具有远优于传统均匀掺杂NEA阴极的超快响应特性．同时在整个光谱响应范围内，量子效率达到约10％--20％，空间分辨力显著高于以往的计算结果．分析结果表明，在保证较高的量子效率条件下，这种新阴极能够突破常规GaAsNEA阴极的时间分辨率极限，提高GaAsNEA阴极本身的分辨力，有望用于超快摄影、电子加速器和自由电子激光器的电子源等领域，进一步扩展NEA光电阴极的应用范围．%A newtype GaAs photocathode with ultrafast time response, that is, the large exponentialdoping transmissionmode GaAs pho tocathode, is discussed in detail. The response characteristics, including quantum yield, time and spatial resolution, are numerically simulated. The analysis results show that the transit response time of the photoexcited electrons for the GaAs photocathode is ex tremely shortened, because the builtin electric field in GaAs layer formed by the large exponentialdoping mode is benefitcial to the photoelectron transport process of GaAs photocathodes. The response time can reach about 10 ps when the thickness of GaAs dgorp tion layer is around, which shows that the novel NEA cathode has a better feature of temporal response than that of traditional GaAs photocathode. In addition, the quantum yield will reach ~ 10%20% in the whole special response range, and the spatial resolution is improved obviously. The analysis results indicate that with high quantum efficiency guaranteed, the large exponentialdoping NEA cathode overcomes the limitation of time response of traditional GaAs NEA cathode and improves the spatial resolution, which in dicates that the new NEA cathode is expected to meet the demands of highspeed device and photoelectron device, and promote the further development and applications of NEA cathodes.
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