Breaking New Ground in Infrared Imaging: Lead-Free SWIR Sensors Redefine the Field

In an exciting development revealed at the 2024 IEEE International Electron Devices Meeting (IEDM), researchers from imec and the Q-COMIRSE project introduced a prototype shortwave infrared (SWIR) image sensor that could reshape the future of imaging technology. The sensor utilizes indium arsenide quantum dot photodiodes, offering an innovative and environmentally friendly alternative to conventional lead-containing quantum dots. Demonstrating successful 1390 nm imaging, this breakthrough addresses a significant obstacle to broader adoption by eliminating toxic materials.

Shortwave infrared sensors enable imaging beyond the visible spectrum, enhancing contrast and detail by detecting materials’ unique reflective properties in this range. These capabilities make SWIR sensors indispensable for diverse applications, including autonomous vehicle navigation, medical diagnostics, and consumer electronics such as face recognition and eye tracking. Despite their potential, current SWIR technologies are expensive and largely confined to niche, high-end applications. The development of wafer-level integration, as showcased by this prototype, heralds a future of affordable and widely accessible infrared imaging.

The Promise of Quantum Dots

Quantum dots (QDs) are nanoscale semiconductor particles that can be engineered to absorb and emit light at specific wavelengths. Their tunability and compatibility with existing CMOS manufacturing processes make them ideal for compact, low-cost SWIR applications. However, first-generation QDs often contained toxic heavy metals, such as lead and mercury, posing environmental and regulatory challenges. Imec’s lead-free alternative offers a transformative solution.

Lead-Free Breakthrough

Imec’s new SWIR image sensor employs indium arsenide (InAs) quantum dots as absorbers, successfully achieving 1390 nm imaging on both glass and silicon substrates. This breakthrough was made possible through meticulous material selection, ensuring over 300 hours of air stability—a key requirement for compatibility with semiconductor manufacturing. Beyond image sensing, the sensor’s pixel architecture supports integration with flat-panel displays, opening avenues for multifunctional applications.

Pawel Malinowski, imec’s Technology Manager and Domain Lead for Imaging, highlighted the significance of this advancement: “The first generation of QD sensors demonstrated the potential of this flexible platform. Now, we’re focusing on a second generation aimed at cost-efficient, environmentally friendly manufacturing. This innovation brings us closer to accessible, compact, and multifunctional sensors with enhanced capabilities.”

Industry Impact and Future Potential

Stefano Guerrieri, Engineering Fellow at ams OSRAM, underscored the collaboration’s success: “Replacing lead in colloidal quantum dots with environmentally friendly materials was a primary goal. Our collaboration with imec, Ghent University, QustomDot, and ChemStream has paved the way for a low-cost, lead-free SWIR technology. Once industrially matured, this innovation could revolutionize applications in robotics, automotive, AR/VR, and consumer electronics.”

Collaborative Effort

This groundbreaking development was achieved under the Q-COMIRSE project, funded by SIM-Flanders (HBC.2021.0803), the spearhead cluster for materials in Flanders, Belgium. Consortium partners include imec, Ghent University, QustomDot BV, ChemStream BV, and ams OSRAM sensor Belgium.

By addressing both environmental concerns and manufacturing barriers, this lead-free SWIR sensor represents a transformative step toward the mass adoption of infrared imaging, poised to unlock new possibilities across industries.