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 (Edp) on the separation of photo-generated carriers. In this work, self-powered photodetectors based on both Edp and built-in electric field at the p-n junction (Ep-n) were designed to obtain enhanced device performance. A NiO/Pb0.95La0.05Zr0.54Ti0.46O3 (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) × 109 Jones], a faster response speed (τr = 0.34 ± 0.03 s, τd = 0.36 ± 0.02 s), and a lower dark current [Idark = (1.3 ± 0.19) × 10-12 A] under zero bias than the PLZT-based device because of the synergistic effects of Edp and Ep-n. Moreover, under weak-light illumination (0.1 mW/cm2), it exhibits even higher R [(6.3 ± 1.2) × 10-4 A/W] and D* [(1.29 ± 0.26) × 1010 Jones] values, which surpass those of most previously reported FE-based self-powered photodetectors. Our work emphasizes the role of the coupling effect between Ep-n and Edp in the photovoltaic process of NiO/PLZT heterojunction-based devices and provides an effective way to promote the self-powered UV photodetector applications.
Keywords: depolarization electric field; ferroelectrics; p-n junction; photovoltaics effect; self-powered photodetectors.