Band Engineering of Rare Earth Nickelates for Applications in Optoelectronics and Non-volatile Memory

The rich phase diagrams and exotic physical properties of rare earth nickelates (RNiO₃) have recently attracted much attention. Their band structures are highly sensitive to carrier density and bandwidth due to Mott physics. Here, we report the band engineering of RNiO₃ for applications in optoelectronics and non-volatile memory. Band structures of RNiO₃ have been tuned by controlling oxygen content during film deposition. Epitaxial GdNiO₃ films have been deposited on Nb-doped SrTiO₃ substrates to form heterojunctions. Under optimized condition, such designed heterojunctions work as self-powered photodetectors with high sensitivity. Under 365 nm illumination, the photo-dark ratio reaches 10³ when the power light density is as weak as 0.6 mW/cm² and the responsivity can be as high as 0.23 A/W at 0 V bias even light density is only 50 µW/cm², which are more competitive than some ultraviolet photodetectors based on GaN or ZnO. Also, further investigation confirms that oxygen vacancy migration across the interface of the heterojunction causes giant resistive switching behavior. An ON/OFF ratio of 10⁵ has been observed and no significant decay appears after more than 10⁴ write/read cycles. Our work promotes the development of multifunctional electronic devices based on nickelates.