Highly Sensitive and Tunable Self-Powered UV Photodetectors Driven Jointly by p-n Junction and Ferroelectric Polarization

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 (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) x 10(-4 )A/W] and detectivity [D* = (3.69 +/- 0.2) X 10(9)Jones], a faster response speed (tau(r) = 0.34 +/- 0.03 s, tau(d) = 0.36 +/- 0.02 s), and a lower dark current [I-dark = (1.3 +/- 0.19) X 10(-12) A] under zero bias than the PLZT-based device because of the synergistic effects of E-dp and Ep-n. Moreover, under weak-light illumination (0.1 mW/cm(2)), it exhibits even higher R [(6.3 +/- 1.2) X 10(-4) A/W] and D* [(1.29 +/- 0.26) x 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 Ep-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.