Heterojunction floating-gate phototransistors for ultraweak short-wavelength infrared photodetection

Abstract

Short-wavelength infrared (SWIR) photodetectors with high sensitivity are indispensable for detecting subtle object variations under low-light conditions, a capability that supports advancements in artificial intelligence. However, commercial approaches for low-light photodetection, such as photomultiplier tubes and avalanche photodiodes, often require high operating voltages and lack compatibility with modern microelectronic technologies critical for integrated optoelectronic systems. Herein, we present a hybrid phototransistor integrating carbon nanotube thin film field-effect transistors (CNT-FETs) with lead sulfide colloidal quantum dot (PbS CQD) heterojunction photodiodes, where the PbS CQD photodiode functions as a floating-gate modulating the CNT-FET channel current. Under 1350 nm illumination, the phototransistor demonstrates a minimum detection light power density of 0.39 nW cm⁻², with responsivity and D* of 1.02 × 10⁵ A W⁻¹ and 8.1 × 10¹³ Jones, respectively, while the external quantum efficiency (EQE) reaches an impressive value of 9.4 × 10⁶%. This innovative phototransistor showcases significant potential for both photodetection and imaging applications within the weak SWIR environment.