Defect engineering of vertically aligned WO3/β-Ga2O3 Heterostructure nanowires for improved UV Photodetection

Vertically aligned WO 3 /β-Ga 2 O 3 heterostructure (HS) nanowire (NW) arrays were deposited utilising a GLAD system RF magnetron sputtering system on a p-type Si substrate. The NWs were subsequently annealed in air at different temperatures ranging from 300 °C to 700 °C. The notable enhancement in the crystallinity and surface morphology of the synthesized vertical WO 3 /β-Ga 2 O 3 axial HS NWs was clearly observed in the samples with annealing. In the proposed WO 3 /β-Ga 2 O 3 HS, β-Ga 2 O 3 serves as an electron transport/window layer under UV-A illumination. Moreover, the favourable band alignment at the WO 3 /β-Ga 2 O 3 interface promotes carrier collection at the top electrode while limiting hole transport, thereby improving photodetection. An overall red shift in the optical bandgap was observed with the rise in annealing temperature. The defect levels diminished at the annealed temperature of 600 °C, as indicated by the photoluminescence (PL) analysis, XRD and absorption data. The device fabricated with 600 °C sample also demonstrated superior UV photodetection at 400 nm, achieving a photo-to-dark current ratio (PDCR) of 0.99 × 10 4 , a large responsivity of 78.58 A W − 1 , and rise/fall times of 0.27 s/9 ms. These results reveal that by controlled air annealing, the structural and interfacial properties of WO 3 /β-Ga 2 O 3 axial NWs can be modified to achieve superior UV-A photodetection characteristics.