Black phosphorus avalanche photodetector

The strong light-matter interaction of atomically-thin layered black phosphorus (BP) has attracted great attention recently. Exfoliated few-layer and monolayer BP flakes have a layer-tunable direct bandgap that varies from 2.0 eV for monolayer to 0.3 eV for bulk, which makes BP a very promising optoelectronic material in the visible and telecom wavelengths [1-3]. The high mobility of BP devices suggested its utilization as an active material of an avalanche photodetector (APD). Recently, APDs utilizing two-dimensional (2D) materials such as transition-metal dichalcogenides (e.g. MoS
2
) and layered III-VI semiconductors (e.g. InSe) have been demonstrated [4,5]. Both of these 2D materials possess wide bandgaps that discourage their usage in the infrared [6,7]. The successful demonstration of waveguide-integrated BP photodetector working at 1.55 μm wavelength [1] has stimulated the pursuit of high-performance BP APDs. In this work, we report on the first 2D material-based BP APD featuring high external quantum efficiency (EQE) and avalanche gain. These results provide strong evidence that BP is a promising material for high-performance optical communication and imaging systems.