RESUMO
Recently, certain ferroelectric tunnel junctions (FTJs) exhibit non-volatile modulations on photoresponse as well as tunneling electroresistance (TER) effects related to ferroelectric polarization states. From the opposite perspective, the corresponding polarization states can be read by detecting the levels of the photocurrent. In this study, we fabricate a novel amorphous selenium (a-Se)/PbZr0.2Ti0.8O3 (PZT)/Nb-doped SrTiO3 (NSTO) heterojunction, which exhibits a high TER of 3 × 106. Unlike perovskite oxide FTJs with a limited ultraviolet response, the introduction of a narrow bandgap semiconductor (a-Se) enables self-powered photoresponse within the visible light range. The self-powered photoresponse characteristics can be significantly modulated by ferroelectric polarization. The photocurrent after writing polarization voltages of +4 and -5 V exhibits a 1200% increase. Furthermore, the photocurrent could be clearly distinguished after writing stepwise polarization voltages, and then a multistate information storage is designed with nondestructive readout capacity under light illumination. This work holds great significance in advancing the development of ferroelectric multistate photoelectronic memories with high storage density and expanding the design possibilities for FTJs.
RESUMO
Dual-polarity response photodetectors (PDs) take full advantage of the directivity of the photocurrent to identify optical information. The dual-polarity signal ratio, a key parameter that represents the equilibrium degree of responses to different lights, is proposed for the first time. The synchronous enhancement of dual-polarity photocurrents and the amelioration of the dual-polarity signal ratio are beneficial to the practical applications. Herein, based on the selective light absorption and energy band structure design, a self-powered CdS/PEDOT:PSS/Au heterojunction PD consisting of a p-n junction and a Schottky junction exhibits unique wavelength-dependent dual-polarity response, where the photocurrent is negative and positive in the short and long wavelength regions, respectively. More importantly, the pyro-phototronic effect inside the CdS layer significantly improves the dual-polarity photocurrents with the maximum enhancement factors of 120%, 343%, 1167%, 1577%, and 1896% at 405, 450, 532, 650, and 808 nm, respectively. Furthermore, the dual-polarity signal ratio tends to 1:1 due to different degrees of the enhancement. This work provides a novel design strategy for dual-polarity response PDs with a simple working principle and improved performance, which can supply a substitution for two traditional PDs in the filterless visible light communication (VLC) system.
