Highly Sensitive Heterojunction‐Gated Phototransistor With Detection Wavelength Ranged From 350 to 1700 Nm

ABSTRACT Sensitive photodetection covering UV, visible, and short‐wave infrared (SWIR) lights will greatly promote applications in all‐weather surveillance, remote sensing, and non‐destructive inspection, but remains challenging in terms of bandwidth or dark noise based on either conventional semiconductors or emerging low‐dimensional materials. Here, we take full advantage of the excellent designability and compatibility of the heterojunction‐gated field‐effect transistor (HGFET) phototransistor, and extend the SWIR detection upper limit from 1400 to 1700 nm through optimizing the lead sulfide (PbS) colloidal quantum dots (CQDs) based diode on the gate. Specifically, the mean diameter of CQDs is increased from 3.8 to 6.0 nm to enable efficient long‐wavelength (1700 nm) absorption, and a hybrid ligand passivation strategy is used to significantly suppress defect states on the nonpolar (100) facets, thereby enhancing heterojunction photovoltage. The resulting HGFETs exhibit a broadband radiation detection from 350 to 1700 nm with a room‐temperature detectivity of up to 5.7 × 10 ¹³ cm Hz ^1/2 W ⁻¹ and a minimum detectable power density of 6.4 nW cm ⁻² at 1650 nm. The hybrid‐passivated CQD HGFETs provide a possible route toward next‐generation, highly sensitive, and broadband infrared photodetectors from UV to short‐wave infrared (beyond 1700 nm) light.