金属微腔效应提高新型TiO2/NaTaO3异质结光电探测器性能的研究

High performance photodetectors based on perovskite-type semiconductors have attracted more and more investigations. Currently, the major restriction to obtain higher device performance includes a low utilization of photons, low sensitivity and large dark current of monolayer semiconductor. In order to settle this problem, we fabricate a new structure of UV detector that with an absorption spectrum cover the whole UVB-UVC region, which is glass/MoO3/Ag/MoO3/NaTaO3/TiO2/ Ag. The two Ag electrodes constitute a metal microcavity structure. Such transmission light makes round trips between the two metal mirrors until the light waves became a multiple reflections between the metal mirrors, a stable standing wave formed. This optical resonance would lead to the maximum light absorption in the active layer, increase the utilization of photos and make a larger absorption coefficient. The energy level matching between TiO2 and NaTaO3 induces heterojunction at the contact interface, which would limit the movement of carriers in dark and promote the fast separation and transfer under illumination. Therefore, a low dark current and fast response can be obtained. At the same time, effects of different modifiers on the active layer quality and device performance are studied, providing a new platform to explore UV detector with high performance. The sensitivity of the device is expected to be more than three orders of magnitude, the dark current is less than 1 nA at 2 V bias.

高性能钙钛矿型半导体光电探测器是近几年研究热点之一。目前限制器件性能提高的主要原因是单一的半导体材料灵敏度低、暗电流大、对光子利用率不高。为了解决这些问题，我们制作了结构为MoO3/Ag/MoO3/NaTaO3/TiO2/Ag，可覆盖全UVB-UVC光谱的紫外探测器。顶底两端Ag电极组成的金属微腔在满足共振条件时，光学共振效应会增强腔内的光电场，提高有源层对入射光的吸收。TiO2和NaTaO3之间由于能级匹配所形成的异质界面既可以限制无光照时载流子的流动，降低暗电流；又可以促进光照下载流子的快速分离和转移，提高器件的响应速度。同时，对基体材料进行修饰改性，研究不同修饰物对有源层质量及器件性能的影响，为探索高性能的紫外探测器件提供新的解决思路。预计器件的灵敏度高于三个数量级，2 V偏压下暗电流小于1 nA。

紫外光探测器具有抗干扰能力强和适于在恶劣环境下工作等优良的特性，具有极高的军事和民用价值。针对目前单一宽禁带半导体紫外探测器存在的灵敏度低、暗电流大、对光子利用率不高等问题，本研究构筑高效稳定的Ag/TiO2/MoO3/Ag，Ag/TiO2/NaTaO3/Ag复合光-电转换材料体系，材料体系对 UVB～UVC 波段的紫外光具有良好的检测能力。TiO2和NaTaO3、MoO3之间由于能级匹配所形成的异质界面既可以限制无光照时载流子的流动，降低暗电流；又可以促进光照下载流子的快速分离和转移，提高器件的响应速度。对NaTaO3组分进行表面修饰，研究了修饰物对基体材料表面形貌、成膜效果、光电性能的影响，以提高有源层质量，为高性能紫外探测器的制作奠定基础。所制作的探测器元件光谱选择性高、暗电流低、灵敏度大、响应时间快，本研究为新型复合材料制作紫外探测器提供了有力技术支撑。基于TiO2/NaTaO3复合材料的探测器暗电流小于1 nA，该复合材料器件比单一的NaTaO3基探测器灵敏度提高近一个数量级。此外，研究初步探索了金属微腔对TiO2有源层光吸收的影响，利用微腔效应最大程度地加强有源层的光吸收，为提高紫外探测器的光子利用率提供新的解决思路。