GaN光电阴极表面势垒对电子逸出几率的影响

摘要

针对GaN光电阴极表面势垒对电子逸出几率的影响问题,应用玻尔兹曼分布和基于Airy函数的传递矩阵法计算了GaN光电阴极的电子逸出几率,发现电子逸出几率主要由Ⅰ势垒决定,Ⅱ势垒对电子逸出几率的影响有限.利用自行研制的GaN光电阴极激活评估实验系统,测试了透射式GaN光电阴极样品的激活光电流.实验发现,Cs单独激活引起电子逸出几率的显著增加,而Cs单独充分激活后的Cs/O交替激活对电子逸出几率的影响有限.理论计算结果与激活光电流测试结果一致,其原因是Cs单独激活对降低真空能级的贡献远大于Cs/O共同激活.%Aiming to inverstigate the effect of surface potential barrier on electron escape probability of negative electron affinity GaN photocathode,the electron escape probability is calculated by using the Boltzmann distribution and the method of transfer matrix based on Airy function.It is found that barrierⅠis a key influencing factor of electron escape probability,while barrierⅡhas a limited influence.The activation photocurrent curve of the transmission-mode GaN photocathode is measured by using our built activation and evaluation experimental system of NEA GaN photocathode.The obvious increase of electron escape probability can be achieved mainly by activating Cs only.The increase of electron escape probability is not large in Cs/O activation process with only Cs activated sufficiently.The theoretical calculations are in good agreement with the photocurrent curves from experimental test.The reason is that the contribution of activating only Cs to the reducing of vacuum level for obtaining NEA state is much larger than that of activating Cs/O.