基于HFET结构的表面等离激元增强型AlGaN基日盲紫外探测器/光开关研究

AlGaN based solar-blind ultraviolet photodetectors have important research value and various potential applications in both military and civil fields. At present, owing to the high density of defects in the high-Al-content AlGaN materials, the low doping efficiency and the device fabrication technique, the performance of AlGaN based photodetectors are still far below expectation. In this project, we propose the surface plasmon enhanced AlGaN solar-blind ultraviolet photodetectors based on the heterojunction field-effect transistor (HFET) structure. The two-dimensional electron gas at the interface of i-AlxGa1-xN/AlyGa1-yN heterojunction with p-GaN as the gate contributes to the response of solar-blind ultraviolet radiation. The Al nanoparticle arrays fabricated by nanosphere lithography will be integrated with the AlGaN heterostructure, while the coupling effects of localized surface plasmon with the device further enhance the photoresponse. Meanwhile, we will investigate the key MOCVD epitaxial technique and defect-control regularity of AlN template and high-Al-content AlGaN materials of high quality on nano-patterned sapphire substrates. With modified device fabrication process, we can obtain AlGaN based HFET solar-blind ultraviolet photodetectors with high responsibility and low dark current. We further investigate the performance of our AlGaN based HFET as the optical switch for solar-blind ultraviolet communication system.

AlGaN基日盲紫外探测器在军用和民用领域均有重要研究价值和广泛应用前景。目前由于异质外延生长的高Al组份AlGaN材料中缺陷密度偏高，同时受限于AlGaN材料的掺杂和器件工艺，AlGaN基日盲紫外探测器的性能仍然低于预期效果。本课题提出研制基于HFET结构表面等离激元增强型AlGaN基日盲紫外探测器构想，即利用带有p-GaN栅极的非掺杂AlxGa1-xN/AlyGa1-yN异质结界面二维电子气实现对日盲紫外响应；采用纳米球刻蚀技术在器件表面制备Al纳米颗粒阵列，利用其局域表面等离激元和AlGaN异质结的耦合效应进一步增强响应。同时我们研究纳米图形化蓝宝石衬底上运用MOCVD外延生长高质量的AlN模板和高Al组份AlGaN材料的关键技术和缺陷控制规律，完善高Al组份AlGaN基器件制备工艺，最终获得高性能AlGaN基HFET日盲紫外探测器，探究其作为光开关用于紫外保密通讯系统的前景。

为进一步提升AlGaN基日盲紫外探测器性能，实现其在军用和民用领域广泛应用前景，本项目提出研制基于HFET结构的表面等离激元增强型AlGaN基日盲紫外探测器的构想。针对异质外延高Al组分AlGaN材料中位错密度高、易龟裂等问题，我们在自主制备纳米图形化蓝宝石衬底上综合运用多种模式相结合的新生长法，获得具有极低缺陷密度的AlN模板，其晶体质量达到国际先进水平，结合高分辨TEM表征阐释了AlN中位错控制规律。此外还发展了普通蓝宝石衬底上快速外延生长晶体质量良好的AlN模板技术。按照项目器件设计和软件仿真结果，我们基于高质量AlN模板优化生长带有p-GaN栅极高Al组份AlxGa1-xN/AlN/AlyGa1-yN异质结，开展芯片工艺研究完成AlGaN基HFET日盲紫外探测器制作。采用FDTD设计金属Al纳米颗粒阵列，使其局域表面等离激元共振波长与日盲紫外探测波段匹配，并利用纳米球刻蚀技术制备相应尺寸均匀、大面积少缺陷的Al纳米颗粒阵列，实现与AlGaN基HFET日盲紫外探测器光敏面集成。所研制的普通AlGaN基HFET日盲紫外探测器，源漏偏压3V时，暗电流在10-8A/mm量级，255 nm响应度可达3×103 A/W，光敏面集成直径~40 nm Al颗粒阵列的同组份AlGaN基HFET日盲紫外探测器响应度于255 nm响应度可超过4×103 A/W，性能对比传统光伏结构日盲紫外探测器有显著提升。本项目成果有助于推动AlGaN基日盲紫外探测器的实用化，并拓展其应用范围。

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