拓扑绝缘体异质结可控制备及其光电探测器件的研究

The absorption of topological insulators covers a wide spectral range from the visible to near-infrared lights, which reveals a broad application prospect in the field of high-performance optoelectronic devices. The present detectors based on photoconductive effect of topological insulators generally suffer from a larger dark current and a weaker photocurrent, which limits the practical application of devices. The project proposes to prepare high-quality n-type and p-type topological insulator films on flexible mica substrates via the van der Waals epitaxial growth to create a topological p-n junction. The built-in potential in the junction can significantly improve the light absorption efficiency and photo-generated carrier separation efficiency of topological insulators. By applying a gate voltage on the heterostructure, we regulate the Fermi level of topological insulators and the built-in potential height of the heterostructure, and thereby improve the rectification ratio of the p-n junction. Through the interface passivation and modification, we further improve the photoelectric conversion performance of the heterojunction. Based on an in-depth understanding of the factors limiting the efficiency of detectors, we explore the corresponding methods to further enhance the light detection performance of the device, and finally obtain a flexible topological insulator photodetector with low-power, ultrafast speed, and broad spectral response. This project is of great significance for promoting practical applications of topological insulators in the field of optoelectronics.

拓扑绝缘体的光吸收覆盖可见光到近红外的宽光谱范围，在高性能光电探测器件领域具有重要的应用前景。目前基于光电导效应的拓扑绝缘体器件普遍具有较大的暗电流，而且光电流也比较微弱，对实际光电器件应用造成限制。本项目提出在柔性氟晶云母基底上范德华外延生长高质量的n-type和p-type拓扑绝缘体薄膜形成拓扑p-n结，利用内建电场的作用改善拓扑绝缘体的光吸收效率以及光生载流子的分离效率。通过对异质结构施加不同的栅压，实现对拓扑绝缘体费米能级以及异质结内建势垒的调控，进而提高拓扑p-n结的整流比；结合异质结构界面钝化与修饰，进一步提高器件的光电转换性能；在深入理解限制器件光探测效率因素的基础上，探索提高器件光探测性能的方法，获得基于拓扑绝缘体异质结构的低功耗、超快、宽光谱、以及柔性的光电探测器件。本项目的开展对促进拓扑绝缘体在光电子学领域中的应用具有重要意义。

以实现基于拓扑绝缘体异质结构的高性能光电探测器件应用为目标，设计生长了高质量的二维拓扑绝缘体薄膜及其异质结构，系统研究了它们的光电输运特性，明确了异质结构内建势垒对整流比和光电转化性能的调制效应，构筑了基于拓扑p-n结的光电探测器件，重点探讨了器件在近红外波段的潜在应用，并从能带结构层面深入探讨了制备器件的工作机制，影响其光电探测效率的因素与作用机理，并探索了提高器件光探测性能的方法。同时，探讨了界面非晶层的钝化与修饰效应，及其对异质结光生载流子寿命与分离效率的影响。最终实现了基于拓扑绝缘体异质结构的高响应度、高探测度、低能耗、超快，以及宽光谱的新型自驱动式光电探测器，利用内建电场的作用改善了拓扑绝缘体的光吸收效率以及光生载流子的分离效率。本研究获得的拓扑绝缘体光电探测器件在新一代光电子器件领域具有重要的应用前景。