Feng Cheng, Zhang Yijun, Shi Feng, Qian Yunsheng, Cheng Hongchang, Zhang Junju, Liu Xinxin, Zhang Xiang
Appl Opt. 2017 Mar 20;56(9):2568-2573. doi: 10.1364/AO.56.002568.
The lifetime and reliability of a photocathode during operation are always raised problems and the photocathode performance depends on the vacuum condition. With the purpose of investigating the stability and reliability of a GaAs-based photocathode in a harsher vacuum environment, reflection-mode exponential-doped GaAs and AlGaAs photocathodes are metalorganic vapor-phase epitaxial grown and then (Cs, O) activated inside an unbaked vacuum chamber. The degraded photocurrents are compared after activation and recaesiations between GaAs and AlGaAs photocathdoes under illumination with an equal initial photocurrent and an equal optical flux, respectively. It is found that the performance on degradation and recaesiations between GaAs and AlGaAs photocathodes are different. In the unbaked vacuum system, the stability of an AlGaAs photocathode after (Cs, O) activation is always better than that of a GaAs photocathode. After multiple recaesiations, the photocurrent decay curves of the AlGaAs photocathode are nearly coincident, which means a nearly constant operational lifetime. Moreover, operational lifetime of an AlGaAs photocathode is longer than that of a GaAs photocathode, which further illuminates that AlGaAs photocathodes are superior to GaAs photocathodes in stability and repeatability under markedly harsher vacuum conditions.
光电阴极在运行过程中的寿命和可靠性一直是备受关注的问题，且光电阴极的性能取决于真空条件。为了研究基于GaAs的光电阴极在更恶劣真空环境中的稳定性和可靠性，采用金属有机气相外延生长反射模式指数掺杂的GaAs和AlGaAs光电阴极，然后在未烘烤的真空室内进行（Cs，O）激活。分别在具有相等初始光电流和相等光通量的光照下，比较GaAs和AlGaAs光电阴极激活和再铯化后的光电流衰减情况。结果发现，GaAs和AlGaAs光电阴极在降解和再铯化方面的性能有所不同。在未烘烤的真空系统中，（Cs，O）激活后AlGaAs光电阴极的稳定性始终优于GaAs光电阴极。经过多次再铯化后，AlGaAs光电阴极的光电流衰减曲线几乎重合，这意味着其工作寿命几乎恒定。此外，AlGaAs光电阴极的工作寿命比GaAs光电阴极长，这进一步表明在明显更恶劣的真空条件下，AlGaAs光电阴极在稳定性和可重复性方面优于GaAs光电阴极。
