Ultrahigh Responsivity and External Quantum Efficiency of an Ultraviolet-Light Photodetector Based on a Single VO2 Microwire

We demonstrated a single microwire photodetector first made using a VO2 microwire that exhibted high responsivity (Rλ) and external quantum efficiency (EQE) under varying light intensities. The VO2 nanowires/microwires were grown and attached on the surface of the SiO2/Si(100) substrate. The SiO2 layer can produce extremely low densities of long VO2 microwires. An individual VO2 microwire was bonded onto the ends using silver paste to fabricate a photodetector. The high-resolution transmission electron microscopy image indicates that the nanowires grew along the [100] axis as a single crystal. The critical parameters, such as Rλ, EQE, and detectivity, are extremely high, 7069 A W–1, 2.4 × 1010%, and 1.5 × 1014 Jones, respectively, under a bias of 4 V and an illumination intensity of 1 μW cm–2. The asymmetry in the I–V curves results from the unequal barrier heights at the two contacts. The photodetector has a linear I–V curve with a low dark current while a nonlinear curves was observed under varing light...