一维 ZnO 纳米棒/n-GaN 异质结构光电导探测器的紫外光辅助场发射实现高效电子源。

State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, People's Republic of China.

Nanoscale. 2019 Jan 17;11(3):1351-1359. doi: 10.1039/c8nr08154a.

Field emission electron beam (EB) pumped AlGaN-based semiconductors are considered to be a potentially promising way to overcome the technical bottlenecks that restrict the development of AlGaN-based UV luminescence devices and realize efficient UV light sources. However, the required field emission electron sources based on nanomaterials are still inefficient due to their low field emission current density. Herein, a type of UV-light-assisted self-positive-feedback enhanced field emission electron source is proposed to develop a high-efficiency electron source which is promising for application in EB pumped AlGaN-based UV light sources that can also be generalized to deep UV (DUV) luminescence devices. The UV-light-assisted field emission source is composed of an n-GaN metal-semiconductor-metal (MSM) structure photodetector assembled with 1D ZnO nanorods by a self-assembled hydrothermal growth method, which simultaneously possesses attributes of the photoelectric effect and electron emission. The optical, photoelectric, and field emission properties are investigated in detail. The results show that the 1D ZnO nanorods/n-GaN heterostructure photodetector presents an obvious photoconductive effect. It has a peak spectral responsivity of 0.793 A W-1 at a bias voltage of 1.3 V, corresponding to an EQE higher than 267.8%, with an internal photoconductive gain reaching up to 2.51 × 103. As to the field emission properties, its turn-on electric field can be greatly reduced from 3.6 V μm-1 in the dark to 1.36 V μm-1 under UV illumination, and the field emission current density increases from lower than 3 mA cm-2 to as high as 8 mA cm-2 at an electric field of 4.5 V μm-1. The mechanism involved can be attributed to an increase of electron concentration in both the conduction bands and an increase of conduction band bending under UV illumination that reduces the effective potential barrier height of the ZnO nanorods. Through this research, an efficient field emission electron source with a self-enhancing effect is developed by combining the photoelectric effect with the electron emission process.

基于场发射电子束（EB）泵浦的 AlGaN 半导体被认为是一种有前途的方法，可以克服限制 AlGaN 基紫外发光器件发展并实现高效紫外光源的技术瓶颈。然而，由于其低场发射电流密度，基于纳米材料的所需场发射电子源仍然效率低下。在此，提出了一种紫外光辅助自正反馈增强场发射电子源，以开发一种高效的电子源，该电子源有望应用于基于 EB 泵浦的 AlGaN 紫外光源，也可推广到深紫外（DUV）发光器件。紫外光辅助场发射源由通过自组装水热生长法组装的一维 ZnO 纳米棒的 n-GaN 金属半导体金属（MSM）结构光电探测器组成，同时具有光电效应和电子发射的属性。详细研究了其光学、光电和场发射性能。结果表明，一维 ZnO 纳米棒/n-GaN 异质结构光电探测器呈现出明显的光电导效应。在 1.3 V 的偏压下，其峰值光谱响应率为 0.793 A W-1，对应于高于 267.8%的 EQE，内部光电导增益高达 2.51×103。至于场发射性能，其开启电场可以从黑暗中的 3.6 V μm-1 大大降低到紫外光照射下的 1.36 V μm-1，并且在 4.5 V μm-1 的电场下，场发射电流密度从低于 3 mA cm-2 增加到高达 8 mA cm-2。涉及的机制可以归因于在紫外光照射下导带中的电子浓度增加和导带弯曲增加，从而降低了 ZnO 纳米棒的有效势垒高度。通过这项研究，通过将光电效应与电子发射过程相结合，开发出具有自增强效应的高效场发射电子源。