Self-Driven Highly Responsive PN Junction InSe Heterostructure Near-Infrared Light Detector

Photodetectors converting light signals into detectable photocurrents are ubiquitously in use today. To improve the compactness and performance of next-generation devices and systems, low dimensional materials provide rich physics to engineering the light matter interaction. Photodetectors based on two dimensional (2D) material van der Waals heterostructures have shown high responsivity and compact integration capability, mainly in the visible range due to their intrinsic bandgap. The spectral region of near-infrared (NIR) is technologically important featuring many data communication and sensing applications. While some initial NIR 2D material-based detectors have emerged, demonstrating doping junction based 2D material photodetectors with the capability to harness the charge separation photovoltaic effect are yet outstanding. Here, we demonstrate a 2D p-n van der Waals heterojunction photodetector constructed by vertically stacking p type and n type few layer indium selenide (InSe) 2D flakes. This heterojunction charge separation based photodetector shows a three fold enhancement in responsivity at near infrared spectral region (980 nm) as compared to a photoconductor detector based on p or n only doped regions, respectively. We show, that this junction device exhibits self-powered photodetection operation and hence enables few pA-low dark currents, which is about 4 orders of magnitude more efficient than state of the art foundry based devices.