Vertical Photodetectors Based on In Situ Aligned Single-crystalline PbS Nanocuboids Sandwiched between Graphene Electrodes

摘要

Lead sulfide (PbS), a classical narrow-bandgap material, has manifested itselfas a reliable choice for short-wave infrared (SWIR) detection with highsensitivity. The primary efforts of optimizing PbS-based photodetectors rely ondiscovering new low-dimensional morphology and designing delicate devicearchitecture, which may raise problems in the synergistic improvement ofresponse speed, sensitivity, and response region. Herein, a graphene-PbSnanocuboids-graphene vertical photodetector is reported, fabricated by in situelectrochemical growth of monocrystalline PbS nanocuboids on grapheneusing an electrochemical technique. Under illumination, the surface states ofPbS nanocuboids trap photogenerated holes and form a photovoltage, whichwidens the conductive region in the channel. This photogating effectcontributes to the photocurrent and renders the device with high responsivity.Moreover, the highly crystalline PbS nanocuboids serve as excellent verticalchannels, allowing a fast speed to be achieved. At room temperature, thedevice shows a responsivity of ≈130 A W~（?1） at 2700 nm, an external quantumefficiency of ≈6000, a detectivity of 3 × 10~9 cm Hz1/2 W~（?1） (@1 kHz), andresponse/recovery speeds of 15/42 ms. This vertically integrated device,composed of PbS nanocuboids and graphene, offers a promising approach tocomplementary metal oxide semiconductor (CMOS)-compatible SWIRdetection, thus opening up an avenue to tailor device performance byexploiting the anisotropic morphology of nanomaterials.