Publication date: 15th December 2025
The growing demand for short-wavelength infrared (SWIR) imaging, particularly in the 1000–2000 nm range, is driven by its critical role in applications such as medical diagnostics, security surveillance, smart agriculture, automotive sensing, consumer electronics, and industrial inspection. Traditional SWIR sensors based on InGaAs, while effective, are hindered by high material costs and complex fabrication processes.
To address these limitations, colloidal quantum dots (CQDs) have emerged as a promising, cost-effective, solution-processable alternative compatible with wafer-scale integration. While lead-based materials like PbS have dominated the field, their incompatibility with the European Union’s Restriction of Hazardous Substances (RoHS) directive poses significant challenges. In this work, we present SWIR image sensors based on RoHS-compliant III-V CQDs, specifically InAs CQDs.
High-performance image sensors require photodiodes with high signal-to-noise ratio, achieved through high quantum efficiency (QE) and low leakage current, preferably at low bias to minimize power consumption. In this talk, we show how the choices of quantum dot ligands and charge transport materials shape the energy landscape of quantum dot photodiodes (QDPDs). Our optimized QDPDs exhibit a detectivity of 2.5 × 10¹¹ Jones at 1210 nm at -1 V. These QDPDs are monolithically integrated onto silicon readout integrated circuits (ROICs), enabling SWIR imaging for material discrimination, smoke penetration, and silicon wafer inspection.
Defect analysis reveals dominant deep trap states within the InAs CQD layer, being tail states of the conduction band that reach down to about 0.4 eV below the band edge, with a density at the order of 1016 cm-3. This implies that defect reduction is essential for further QDPD performance improvement.
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