中文摘要：

本文结合激活过程中光电流变化规律和成功激活后阴极表面模型，研究了NEA GaN和GaAs光电阴极激活机理的异同。实验表明：NEAGaN激活过程中光电流不象GaAs那样按近似指数规律的包络慢速循环上升，而是在约1min之内就可达到峰值，Cs／O激活时引入0后光电流的增长幅度不大，NEA特性仅在Cs激活时即可获得。GaAs光电阴极激活过程中O的引入是获得NEA特性的必要条件，也是真空能级下降的重要转折点，0引入后光电流幅值有较大幅度的增长。采用双偶极层模型可以解释GaN和GaAs光电阴极Cs／O激活后表面势垒的降低，但偶极层在降低表面势垒的程度方面有较大差异，CaN光电阴极降得更低。

英文摘要：

The similarities and differences between the negative electron affinity （NEA） GaN and GaAs cathode activation mechanisms were studied by evaluating the photocurrent in the photocathode activation and with a newly-developed model for the activated photo-cathode surfaces. The results show that the variations in the photocurrent of NEA GaN and GaAs in the activation are different. The current of NEA GaN peaks in less than 1 minute; in contract, the current of NEA GaAs slowly increases in a cyclic way with its envelope resembling the exponential curve. We found that introduction of oxygen to NEA GaN in the Cs/O activation results in a rather small increase of its photecurrent, and that Cs activation is responsible for the NEA characteristics. In the case of NEA GaAs cathode, introduction of oxygen in the activation, a prerequisite of its NEA characteristics, turns the vacuum energy level downwards and considerably increases the photocurrent. We suggest that the double dipole layer model accounts for the lowering of the surface potential barriers of both the GaN and GaAs photo-cathodes after Cs/O activation. Interesting finding is that the double dipole layer resulted in a lower surface barrier of NEA GaN than that of NEA GaAs.