Acoustically enhanced photodetection by a black phosphorus–MoS2 van der Waals heterojunction p–n diode

We developed a new way to enhance the photoresponsivity of a van der Waals heterojunction p-n diode using surface acoustic waves (SAWs). The diode was constructed on top of a piezoelectric LiNbO3 substrate and composed of p-type black phosphorus (BP) and n-type molybdenum disulfide (MoS2) flakes that partly overlapped with each other. This layout facilitated the applied SAWs to rapidly drive carriers out of the depletion region. In this structural design, SAWs promoted the separation of photogenerated carriers, and thus greatly increased the photocurrent. The measured photocurrent for the device with SAWs was about 103 times higher than that of the device without SAWs. The device using SAWs showed a photoresponsivity as high as 2.17 A W-1 at the wavelength of 582 nm. This excellent performance was attributed to the SAWs suppressing electron-hole recombination in the device under light illumination. Our device exhibits promise as a high-performance photodetector and reveals new possibilities for acoustic devices in optoelectronics.