Ferroelectric Localized Field–Enhanced ZnO Nanosheet Ultraviolet Photodetector with High Sensitivity and Low Dark Current

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2018-05, Vol.14 (22), p.e1800492-n/a
• Main Authors: Wang, Peng, Wang, Yang, Ye, Lei, Wu, Mingzai, Xie, Runzhang, Wang, Xudong, Chen, Xiaoshuang, Fan, Zhiyong, Wang, Jianlu, Hu, Weida
• Format: Article
• Language: English
• Subjects: Dark current; detectivity; ferroelectric localized field; Ferroelectric materials; Ferroelectricity; Low light level; Nanosheets; Nanotechnology; Optical properties; Photoelectric effect; Photoelectric emission; Photometers; Sensitivity; Ultraviolet detectors; ultraviolet photodetectors; Zinc oxide; zinc oxide nanosheet; Zinc oxides
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201800492

Zinc oxide (ZnO) nanosheets have demonstrated outstanding electrical and optical properties, which are well suited for ultraviolet (UV) photodetectors. However, they have a high density of intrinsically unfilled traps, and it is difficult to achieve p‐type doping, leading to the poor performance for low light level switching ratio and a high dark current that limit practical applications in UV photodetection. Here, UV photodetectors based on ZnO nanosheets are demonstrated, whose performance is significantly improved by using a ferroelectric localized field. Specifically, the photodetectors have achieved a responsivity of up to 3.8 × 105 A W−1, a detectivity of 4.4 × 1015 Jones, and a photocurrent gain up to 1.24 × 106. These device figures of merit are far beyond those of traditional ZnO ultraviolet photodetectors. In addition, the devices' initial dark current can be easily restored after continuous photocurrent measurement by using a positive gate voltage pulse. This study establishes a new approach to produce high‐sensitivity and low‐dark‐current ultraviolet photodetectors and presents a crucial step for further practical applications. Ferroelectric localized field–enhanced field‐effect transistor structure ultraviolet photodetectors are fabricated with ZnO nanosheet and poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)). The strong ferroelectric localized field can effectively deplete the intrinsic carriers of the channel; thus, the device is capable of low dark current without applying external gate voltage, resulting in high signal‐to‐noise ratio and low power consumption.