imec group launches SWIR sensor with lead-free quantum dot photodiodes

18 Dec 2024

Technology is a step toward “greener” IR imagers for autonomous driving, medical diagnostics.

Lead free quantum dot photodiode integrated into SWIR optical sensor.

Last week, at the 2024 IEEE International Electron Devices Meeting, in San Francisco, imec, a research and innovation hub in nanoelectronics and digital technologies, and its partners in the Belgian project Q-COMIRSE, presented the first prototype shortwave infrared image (SWIR) sensor based on indium arsenide quantum dot photodiodes.

The sensor demonstrated successful 1390 nm imaging results, offering an environmentally-friendly alternative to first-generation quantum dots that contain lead, which limited their widespread manufacturing. The proof-of-concept is a critical step toward mass-market infrared imaging with low-cost and non-toxic photodiodes.

By detecting wavelengths beyond the visible spectrum, SWIR sensors can provide enhanced contrast and detail, as materials reflect differently in this range.

Face recognition and eye-tracking

These sensors can distinguish objects that appear identical to the human eye and penetrate through fog or mist, suiting them to applications such as face recognition or eye-tracking in consumer electronics, and autonomous vehicle navigation. While current versions are costly and limited to high-end applications, wafer-level integration promises broader accessibility.

Tuned for SWIR, quantum dots offer compact, low-cost absorbers, since integration into CMOS circuits and existing manufacturing processes is possible. However, first-generation QDs often contain toxic heavy metals such as lead and mercury, and the search for alternatives continues.

At 2024 IEDM, imec and its partners within the Q-COMIRSE project (Ghent University, QustomDot BV, ChemStream BV and ams OSRAM) presented a SWIR image sensor featuring a lead-free quantum dot alternative as absorber; indium arsenide (InAs). The proof-of-concept sensor, tested on both glass and silicon substrates, was the first of its kind to produce successful 1390 nm imaging results, imec announced.

Pawel Malinowski, imec technology manager and domain lead imaging, emphasized the significance of the achievement: “The first generation of QD sensors was crucial for showcasing the possibilities of this flexible platform. We are now working towards a second generation that will serve as a crucial enabler for the masses, aiming at cost-efficient manufacturing in an environmentally friendly way,” he said.

“With major industry players looking into quantum dots, we are committed to further refine this semiconductor technology towards accessible, compact, multifunctional image sensors with new functionalities.”

Stefano Guerrieri, Engineering Fellow at ams Osram, added, “Replacing lead in colloidal quantum dots with a more environmentally friendly material was our key goal in Q-COMIRSE. Our remarkable development work with imec and the others paves the way toward a low-cost and lead-free SWIR technology that, once mature for industrial products, could enable unprecedented applications in robotics, automotive, AR/VR and consumer electronics among others.”