p型指数掺杂GaN光电材料的原子层沉积生长与阴极研制

GaN-based Ultraviolet photocathode attracts wide attention in the study of optoelectronic devices and becomes a hot topic of current research due to its wide band gap, corrosion resistance, high voltage, and other characteristics. Currently, it is difficult to improve the p-type GaN electron diffusion length in the material has become a key factor restricting its performance. In this work GaN photocathode material with a new structure is proposed, where the p-type doping concentration has an exponential change along the film thickness direction. Compared to the uniform doping structure, this structure can produce a band bending in GaN material to form a built-in electric field, so that photoelectrons can be transported to the surface under the action of two mechanisms of diffusion and drift simultaneously, which will improve the electron diffusion length effectively. In order to precisely control the doping concentration at magnitude of nanometers in thickness, atomic layer deposition technique will be employed to grow GaN photocathode material with p-type exponential doping concentration, which solves the problem of using traditional methods is difficult to obtain this structure, and the photoemission properties of GaN ultraviolet photocathode will be improved ultimately. This high performance exponential doping GaN photocathode has broad application prospects and important values in the ultraviolet detection, lithography, and other fields.

GaN基紫外光电阴极由于其宽禁带、耐腐蚀、耐高压等特点在光电子器件研究中受到了广泛关注，并成为当下研究的热点。目前，难以提高p型GaN材料中的电子扩散长度已经成为制约其性能的关键因素。本项目提出了p型掺杂浓度沿材料厚度方向成指数变化的GaN光电阴极结构，相比之前均匀掺杂，此结构可以使GaN能带产生线性弯曲，并形成内建电场，使得光生电子可以同时在扩散和漂移两种机制作用下向材料表面输运，有效地提高了电子扩散长度；为了达到在纳米厚度的量级上对掺杂浓度进行精确控制，采用了原子层沉积技术进行p型指数掺杂结构GaN光电阴极材料的生长，解决了利用传统生长方法难以获得此结构的问题，最终提高了GaN紫外光电阴极的光电发射性能。这种高性能的指数掺杂GaN光电阴极在紫外探测、平板印刷等领域具有广阔的应用前景和重要价值。

GaN光电阴极是满足微弱紫外探测要求的非常理想的新型紫外光电阴极，在紫外真空探测、高能物理、微电子技术、电子束平面印刷以及电子显微镜等领域有广泛应用。目前GaN光电阴极面临的最大问题是难以同时提高其电子扩散长度和电子逸出几率，在GaN光电发射材料的结构设计与生长时，很难同时兼顾这两个重要的性能指标。.本研究建立了NEA GaN光电阴极表面发射模型：[GaN(Mg) - Cs] : [O - Cs]，利用ALD成功生长了GaN光电发射材料，通过Delta掺杂结构的方法，使得GaN光电发射材料的载流子浓度从均匀掺杂的3.3×1017 cm-3提高到8.7×1017 cm-3，电子逸出几率从0.13提高到0.51，电子扩散长度从159 nm提高到258 nm，最终的量子效率最大值从7%提高到24%。.本项目的研究结果为GaN基紫外探测技术的发展和研究提供了一定的理论基础，实验上从电子逸出几率、电子扩散长度、以及最终的量子效率都有了一定程度的提高。