Highly Sensitive and Ultra-Broadband VO₂(B) Photodetector Dominated by Bolometric Effect

In this study, Wadsley B phase vanadium oxide (VO₂(B)) with broad-band photoabsorption ability, a large temperature coefficient of resistance (TCR), and low noise was developed for uncooled broad-band detection. By using a freestanding structure and reducing the size of active area, the VO₂(B) photodetector shows stable and excellent performances in the visible to the terahertz region (405 nm to 0.88 mm), with a peak TCR of -4.77% K^-1 at 40 °C, a peak specific detectivity of 6.02 × 10⁹ Jones, and a photoresponse time of 83 ms. A terahertz imaging ability with 30 × 30 pixels was demonstrated. Scanning photocurrent imaging and real-time temperature-photocurrent measurements confirm that a photothermal-type bolometric effect is the dominating mechanism. The study shows the potential of VO₂(B) in applications as a new type of uncooled broad-band photodetection material and the potential to further raise the performance of broad-band photodetectors by structural design.