标题： 陷阱在薄层In-Se光电探测器光电流生成机制中的作用 显示英文标题

标题： The role of traps in the photocurrent generation mechanism in thin In-Se photodetectors

摘要： 由于出色的电荷传输性能和光电性能，薄层硒化铟（InSe）最近在二维半导体材料领域引起了关注。 然而，薄层InSe光电探测器中的光生电流机制仍然不明确。 在此，我们提出了一组实验，旨在解释文献中报道的薄层InSe光电探测器中光响应值的强烈散射现象。 通过在不同环境条件下对基于薄层InSe的光电探测器进行光电测量，我们发现光响应度、响应时间和光电流功率依赖性在该材料中存在强烈相关性。 这一观察表明，光栅效应在薄层InSe片中起着重要作用，并且是原始InSe器件超高的光响应度的主要机制。 此外，当将原始InSe光电探测器暴露于环境空气中时，我们观察到光响应的快速且不可逆的变化，伴随着光响应度的降低和操作速度的增加。 我们将这种光电探测器性能的变化（在大气暴露后）归因于InSe中陷阱密度的减少，这是由于大气中的氧物种对硒空位的钝化作用。 这种钝化伴随着InSe费米能级的下移以及费米能级钉扎的减少，从而导致Au和InSe之间肖特基势垒的增加。 我们的研究揭示了由缺陷引起的陷阱在调节基于二维材料的器件特性中的重要作用，并提供了一种可控的方法来设计和功能化薄层InSe光电探测器，以实现具有超高光响应度或快速操作速度的器件。 显示英文摘要

摘要： Due to the excellent electrical transport properties and optoelectronic performance, thin indium selenide (InSe) has recently attracted attention in the field of 2D semiconducting materials. However, the mechanism behind the photocurrent generation in thin InSe photodetectors remains elusive. Here, we present a set of experiments aimed at explaining the strong scattering in the photoresponsivity values reported in the literature for thin InSe photodetectors. By performing optoelectronic measurements on thin InSe-based photodetectors operated under different environmental conditions we find that the photoresponsivity, the response time and the photocurrent power dependency are strongly correlated in this material. This observation indicates that the photogating effect plays an imporant role for thin InSe flakes, and it is the dominant mechanism in the ultra-high photoresponsivity of pristine InSe devices. In addition, when exposing the pristine InSe photodetectors to the ambient environment we observe a fast and irreversible change in the photoresponse, with a decrease in the photoresponsivity accompanied by an increase of the operating speed. We attribute this photodetector performance change (upon atmospheric exposure) to the decrease in the density of the traps present in InSe, due to the passivation of selenium vacancies by atmospheric oxygen species. This passivation is accompanied by a downward shift of the InSe Fermi level and by a decrease of the Fermi level pinning, which leads to an increase of the Schottky barrier between Au and InSe. Our study reveals the important role of traps induced by defects in tailoring the properties of devices based on 2D materials and offers a controllable route to design and functionalize thin InSe photodetectors to realize devices with either ultrahigh photoresposivity or fast operation speed.