中文摘要：

采用分子束外延（MBE）技术生长的GaAs光阴极材料，按照常规方法进行高一低温两步激活时，总是出现低温灵敏度比高温低的反常现象。研究中，当激活时的系统真空度从1×10^-7Pa提升到1×10^-8Pa时，发现结果能够重新出现低温灵敏度比高温灵敏度高30％的预期规律。此外，在系统真空度为10^-7 Pa条件下，由于变掺杂材料的表面掺杂浓度较低，其出现光电流时的首次进Cs时间也较均匀掺杂材料长，而在真空度为约10^-9 Pa条件下，这一情况也不再明显。初步分析造成该现象的原因，是与MBE材料的掺杂元素及其低温处理特性对真空度比较敏感有关。MBE阴极激活结果受系统真空度条件影响较大，因此对MBE变掺杂光阴极的制备工艺应随系统真空度条件不同而调整。

英文摘要：

For GaAs photocathodes made by molecular beam epitaxy（MBE） technique,after preparing by general ＂high-low temperature two steps＂ activation, an abnormal result that the sensitivity of low temperature be lower than the high temperature was obtained. Experimental investigation shows that the general result that the low temperature activation increase the sensitivity of photocathode by at least 30% would be obtained again if the vacuum during activation is increased from 1 × 10^-7Pa to 1×10^-8 Pa. Besides, the phenomena that the time of photocurrent appearing during the first Cs activation of varied doped cathode under 1× 10^-7 Pa vacuum pressure is longer than uniform doped cathode due to the low surface doping concentration,is no longer distinct under 1 × 10^-8Pa vacuum pressure. Possible mechanisms are tentatively discussed. The activation results of MBE GaAs photocathode are strongly affected by the system vacuum pressure,and with which the preparing technique of MBE varied doped photocathode should be adjusted along.