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

Abstract

AbstractLead sulfide (PbS), a classical narrow‐bandgap material, has manifested itself as a reliable choice for short‐wave infrared (SWIR) detection with high sensitivity. The primary efforts of optimizing PbS‐based photodetectors rely on discovering new low‐dimensional morphology and designing delicate device architecture, which may raise problems in the synergistic improvement of response speed, sensitivity, and response region. Herein, a graphene‐PbS nanocuboids‐graphene vertical photodetector is reported, fabricated by in situ electrochemical growth of monocrystalline PbS nanocuboids on graphene using an electrochemical technique. Under illumination, the surface states of PbS nanocuboids trap photogenerated holes and form a photovoltage, which widens the conductive region in the channel. This photogating effect contributes to the photocurrent and renders the device with high responsivity. Moreover, the highly crystalline PbS nanocuboids serve as excellent vertical channels, allowing a fast speed to be achieved. At room temperature, the device shows a responsivity of ≈130 A W−1 at 2700 nm, an external quantum efficiency of ≈6000%, a detectivity of 3 × 109 cm Hz1/2 W−1 (@1 kHz), and response/recovery speeds of 15/42 ms. This vertically integrated device, composed of PbS nanocuboids and graphene, offers a promising approach to complementary metal oxide semiconductor (CMOS)‐compatible SWIR detection, thus opening up an avenue to tailor device performance by exploiting the anisotropic morphology of nanomaterials.