负电子亲和势GaAlN光电阴极具有禁带宽度可调、日盲、低暗电流以及高响应速度等优点，在紫外探测领域具有广泛的应用，成为研究热点。然而目前研制的GaAlN光电阴极存在电子扩散长度小，Cs,O交替激活光电流上升不明显以及阴极寿命较短的问题。针对以上问题，本项目设计了Al组分由体内向表面逐渐减小的变组分GaAlN光电阴极，此结构形成一个由表面指向体内的内建电场，有助于光电子向表面的扩散漂移运动，有效地提高了电子扩散长度；研究变组分GaAlN光电阴极的能带结构及光电发射理论；基于第一性原理计算和XPS表面原子分析结合的方法，完善GaAlN光电阴极Cs,O吸附模型，以改进激活工艺，并研究阴极稳定性机理，以延长阴极寿命。该项目的进行对提高GaAlN光电阴极的光电发射性能具有重要意义。

Negative electron affinity GaAlN photocathodes attract wide attention and become research hotspots in ultraviolet detection field due to their adjustable energy gaps, solar blind property, low dark current, and high response speed. Meanwhile, there still exist some shortcomings in the obtained GaAlN photocathodes, such as, the electron diffusion length is not long enough; the current increase is not obvious at the stage of Cs,O coadsorption; the lifetime of photocathodes is short. To solve these problems, a new structure of GaAlN photocathodes is proposed, where Al component has a gradient decrease along the film thickness direction. This structure forms a built-in electric field which points to bulk materials from cathode surface, and the electric field imporves the diffusion and drift movement of photoexcited electrons towards the surface, which improves the electron diffusion length effectively. Then energy band structure and photoemission theory of GaAlN photocathodes with variational Al component will be researched. Based on first-principles calculations and XPS analysis about surface atoms, the Cs,O coadsorption model will be consummated to give guidance on activation technology, and the cathode stability mechanism will be researched to obtain photocathodes with longer lifetime. This project is meaningful to improve the photoemission property of GaAlN photocathodes.