Highly Sensitive and Tunable Self-Powered UV Photodetectors Driven Jointly by p-n Junction and Ferroelectric Polarization
Jian Chen, Di You, Ying Zhang, Teng Zhang, Chong Yao, Qingfeng Zhang, Mingkai Li, Yinmei Lu, Yunbin He
Abstract
Ferroelectric (FE) materials are thought to be promising materials for self-powered ultraviolet (UV) photodetector applications because of their photovoltaic effects. However, FE-based photodetectors exhibited poor performance because of the weak photovoltaic effect of FE depolarization field ( E dp ) on the separation of photo-generated carriers. In this work, self-powered photodetectors based on both E dp and built-in electric field at the p-n junction ( E p-n ) were designed to obtain enhanced device performance. A NiO/Pb 0.95 La 0.05 Zr 0.54 Ti 0.46 O 3 (PLZT) heterojunction-based device is constructed to take advantage of energy level alignments that favor electron extraction. The device exhibits a tunable performance upon varying the polarization direction of PLZT. The NiO/PLZT heterojunction-based device with the PLZT layer in the poling down state shows a higher responsivity [ R = (1.8 ± 0.12) × 10 –4 A/W] and detectivity [ D * = (3.69 ± 0.2) × 10 9 Jones], a faster response speed (τ r = 0.34 ± 0.03 s, τ d = 0.36 ± 0.02 s), and a lower dark current [ I dark = (1.3 ± 0.19) × 10 –12 A] under zero bias than the PLZT-based device because of the synergistic effects of E dp and E p-n . Moreover, under weak-light illumination (0.1 mW/cm 2 ), it exhibits even higher R [(6.3 ± 1.2) × 10 –4 A/W] and D * [(1.29 ± 0.26) × 10 10 Jones] values, which surpass those of most previously reported FE-based self-powered photodetectors. Our work emphasizes the role of the coupling effect between E p-n and E dp in the photovoltaic process of NiO/PLZT heterojunction-based devices and provides an effective way to promote the self-powered UV photodetector applications.