High-Performance Negative Self-Powered α-MoO₃/Ir/α-MoO₃ Photodetectors: Probing the Influence of Coulomb Deep Traps

Abstract

Nanostructures of ultrathin 2D MoO3 semiconductors have gained significant attention in the field of transparent optoelectronics and nanophotonics due to their exceptional responsiveness. In this study, we investigate self-powered α-MoO3/Ir/α-MoO3 photodetectors, focusing on the influence of induced hot electrons in ultrathin α-MoO3 when combined with an ultrathin Ir plasmonic layer. Our results reveal the presence of both positive and negative photoconductivity at a 0 V bias voltage. Notably, by integrating a 2 nm Ir layer between post-annealed α-MoO3 films, we achieve remarkable performance metrics, including a high I ON/I OFF ratio of 3.8 × 106, external quantum efficiency of 132, and detectivity of 3.4 × 1011 Jones at 0 V bias. Furthermore, the response time is impressively short, with only 0.2 ms, supported by an exceptionally low MoO3 surface roughness of 0.1 nm. The observed negative photoresponse is attributed to O2 desorption from the MoO3 surface, resulting in increased carrier density and reduced mobility in the Ir layer due to Coulomb trapping and oxygen vacancy deep levels. Consequently, this leads to a decreased carrier mobility and diminished current in the heterostructure. Our findings underscore the enormous potential of ultrathin MoO3 semiconductors for high-performance negative conductivity optoelectronics and photonic applications.