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

## TL;DR

A new phototransistor detects light from UV to short-wave infrared with high sensitivity, enabling advanced imaging and sensing applications.

## Contribution

A hybrid ligand passivation strategy extends SWIR detection to 1700 nm in a heterojunction-gated phototransistor.

## Key findings

- The device detects wavelengths from 350 to 1700 nm with a detectivity of 5.7 × 10¹³ cm Hz¹/² W⁻¹.
- Hybrid passivation suppresses defect states, enhancing photovoltage in PbS quantum dot heterojunctions.

## 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 × 1013 cm Hz1/2 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.

This work demonstrates a heterojunction‐gated infrared phototransistor for broadband detection from 350 to 1700 nm. By suppressing defect states on nonpolar (100) facets of large PbS quantum dots via hybrid ligand passivation, the device achieves a room‐temperature detectivity of 5.7 × 1013 Jones at 1650 nm. Wafer‐scale fabrication highlights its potential for highly integrated SWIR imaging systems.