Phase change vanadium dioxide light sensors

Vanadium dioxide (VO2) has drawn significant attention due to a unique band-structure and multifaceted optoelectronic properties. However, VO2-based photodetectors reported till date involve complex structures and/or constrained wavelength response. Moreover, there is limited understanding of parameters which control the insulator-to-metal transition (IMT) and photoresponse in VO2. In this work, we present VO2 based two-terminal planar devices and explore the size-dependency of IMT and photoresponse in VO2 devices. We investigate the photoresponse of VO2 devices at a broadband range from ultra-violet to near infrared at three temperature regions: room temperature, IMT slope, and beyond IMT slope. We further postulate the mechanism for photoresponse at all three temperature regions. A significant enhancement in photoresponse and figure of merit of photodetectors is achieved beyond IMT slope region. An intermediate state driven by deep level defects assists the broadband photoresponse which is supported by cathodoluminescence (CL) analysis. The ability to manipulate the IMT and the broadband photoresponse opens opportunities for designing and controlling functional domains of VO2 for scalable micro- and nano-scale devices and sensor applications.