Hyperspectral Quantum Dot Sensor

Graphene quantum dots CMOS-based sensor for ultraviolet, visible and infrared. (Source: ICFO / D. Bartolome)

Over the past forty years, micro­electronics have advanced by leaps and bounds thanks to silicon and complemen­tary metal-oxide semi­conductors tech­nology, making possible computing, smart­phones, compact and low-cost digital cameras, as well as most of the electronic gadgets we rely on today. However, the diver­sification of this platform into appli­cations other than micro­circuits and visible light cameras has been impeded by the difficulty to combine semi­conductors other than silicon with CMOS. This obstacle has now been overcome.

ICFO researchers have shown for the first time the mono­lithic inte­gration of a CMOS inte­grated circuit with graphene, resulting in a high-reso­lution image sensor con­sisting of hundreds of thousands of photo­detectors based on graphene and quantum dots (QD). They operated it as a digital camera that is highly sensitive to UV, visible and infrared light at the same time. This has never been achieved before with existing imaging sensors. In general, this demon­stration of mono­lithic inte­gration of graphene with CMOS enables a wide range of opto­electronic appli­cations, such as low-power optical data communi­cations and compact and ultra sen­sitive sensing systems.

The work was carried out by ICFO researchers Stijn Goossens and colleagues in colla­boration with the company Graphenea. The graphene-QD image sensor was fabri­cated by taking PbS colloidal quantum dots, depositing them onto the CVD graphene and sub­sequently depositing this hybrid system onto a CMOS wafer with image sensor dies and a read-out circuit. As Stijn Goossens comments, “No complex material proces­sing or growth processes were required to achieve this graphene-quantum dot CMOS image sensor. It proved easy and cheap to fabricate at room tempera­ture and under ambient con­ditions, which signifies a consi­derable decrease in production costs. Even more, because of its properties, it can be easily integrated on flexible substrates as well as CMOS-type inte­grated circuits.”

As Gerasimos Konstan­tatos, expert in quantum dot-graphene research comments, “we engineered the QDs to extend to the short infrared range of the spectrum (1100-1900nm), to a point where we were able to demon­strate and detect the night glow of the atmo­sphere on a dark and clear sky enabling passive night vision. This work shows that this class of photo­transistors may be the way to go for high sensitivity, low-cost, infrared image sensors operating at room tempera­ture addres­sing the huge infrared market that is currently thirsty for cheap tech­nologies”.

“The develop­ment of this mono­lithic CMOS-based image sensor represents a mile­stone for low-cost, high-reso­lution broadband and hyper­spectral imaging systems,” Frank Koppens high­lights. He assures that “in general, graphene-CMOS tech­nology will enable a vast amount of appli­cations, that range from safety, security, low cost pocket and smart­phone cameras, fire control systems, passive night vision and night sur­veillance cameras, auto­motive sensor systems, medical imaging appli­cations, food and pharma­ceutical inspection to environ­mental moni­toring, to name a few”. (Source: ICFO)

Reference: S. Goossens et al.: Broadband image sensor array based on graphene-CMOS integration, Nat. Phot. , online 29 May 2017; DOI: 10.1038/nphoton.2017.75

Link: Functional Optoelectronic Nanomaterials, Inst. of Photonic Science ICFO, Barcelona Institute of Science and Technology, Castelldefels, Spain

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