Self-powered ultraviolet vertical and lateral photovoltaic effect with fast-relaxation time in NdNiO3/Nb:SrTiO3 heterojunctions

Abstract

Substantial ultraviolet (UV) photodetector research has been pursued in recent decades. In this paper, we report the self-powered UV vertical photovoltaic effect (VPE) and lateral photovoltaic effect (LPE) with high sensitivity and fast-relaxation time in NdNiO3/Nb:SrTiO3 (NNO/NSTO) heterojunctions. The rectifying behavior indicates that the large built-in electric field is formed in the p-n junctions. The open circuit voltage of VPE is as high as 0.4 V under 266 nm laser illumination, with the relaxation time of 1.8 μs. The highest position sensitivity of the LPE is about 32 mV/mm, and its optical relaxation time is about 7.4 μs. The two distinct resistance states observed for the NNO film deposited on NSTO and SrTiO3 (STO) substrates suggest that the transport of photo-excited carriers in VPE and LPE is mainly through the NSTO single crystal, resulting in a fast relaxation time of the photovoltaic effect in NNO/NSTO p-n junctions. The fast relaxation and high sensitivity of the VPE and LPE make the NNO/NSTO junction a promising candidate for a wide range of self-powered ultraviolet/near-ultraviolet optoelectronic applications.