利用超高真空制备技术，对以蓝宝石为衬底、AlN为缓冲层的MOCVD外延P-GaN样品进行了光电阴极制备，并利用紫外光谱响应测试仪，对所制备的基于负电子亲和势（NEA） GaN光电阴极在反射式和透射式两种工作模式下的量子效率特性进行了测试与对比分析。实验结果显示，在反射模式下，样品在240 nm处具有高达50%的量子效率，而在透射模式下量子效率最高只有15%，量子效率曲线拟合表明该样品的后界面复合速率为104 cm/s。通过分析发现，造成两种工作模式下量子效率相差较大的主要影响因素是后界面复合速率和GaN外延材料厚度。

MOCVD epitaxial P-GaN, which was grown on the sapphire substrate and AlN buffering layer, was used to make photocathode by ultra-high vacuum preparation technique. The quantum efficiency properties of prepared GaN photocathode under reflection mode and the transmission mode measured and analyzed by UV spectral response testing instrument. Experimental results showed that the sample in reflection mode has up to 50% quantum efficiency at 240 nm, but in transmission mode, the maximum quantum efficiency is only 15%. Curve fitting results of experimental quantum efficiency revealed that sample′s back interface recombination velocity is about 104 cm/s. It was also found that the reasons for the great difference in this two operating modes were back-interface recombination velocity and the thickness of GaN epitaxial materials.