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GaN紫外光阴极是一种表面具有负电子亲和势(NEA)状态的光电发射材料,具有电子发射效率高、暗发射小、稳定性好等众多优点,是近年来得到迅速发展的一种新型高性能紫外探测材料。采用超高真空原子吸附工艺,对金属有机物化学汽相沉积(MOCVD)外延的p型GaN表面依次进行了高温净化、Cs/O激活、低温净化和Cs/O激活的高低温两步光阴极制备实验。实验结果表明,高温净化后的Cs/O激活可制备出量子效率约为20%的GaN紫外光阴极材料,第二步低温净化后GaN表面仍具有光电发射能力,经过Cs/O激活后可将阴极光电流恢复到接近高温激活结束后的水平,说明GaN阴极材料的制备只需单步高温激活完成。通过比较GaN与GaAs光阴极材料的高低温制备效果差异,对GaN光阴极制备工艺的机理进行了探讨。
GaN ultraviolet cathode is a kind of photoemissive material with negative electron affinity (NEA) state and has many advantages such as high electron emission efficiency, small dark emission and good stability. It is a new type that has been rapidly developed in recent years High-performance UV detection materials. High and low temperature two-step photocathode preparation was carried out on the p-type GaN surface epitaxially grown by metal-organic chemical vapor deposition (MOCVD) using an ultra-high vacuum atomic adsorption process, followed by high temperature purification, Cs / O activation, low temperature purification and Cs / O activation experiment. The experimental results show that GaN ultra-violet cathode material with quantum efficiency of about 20% can be obtained by Cs / O activation after high-temperature purification. The second step is that the GaN surface still possesses photo-emission ability after low temperature purification. After Cs / O activation, Cathode photocurrent was restored to near the end of high temperature activation level, indicating that the preparation of GaN cathode material only one step high temperature activation is completed. The mechanism of GaN photocathode preparation was discussed by comparing the difference between high and low temperature of GaN and GaAs photocathode.