Graphene and quantum dots enable a unique CMOS-integrated camera

Researchers from the ICFO have developed the first graphene-QDs-CMOS integrated camera, capable of imaging visible and infrared light at the same time. The camera may be useful for many applications like night vision, food inspection, fire control, vision under extreme weather conditions, and more.

The imaging system is said to be based on the first monolithic integration of graphene and quantum dot photodetectors, with a CMOS (complementary metal-oxide semiconductors) read-out integrated circuit. The implementation of such a platform in applications other than microcircuits and visible light cameras has been impeded by the difficulty to combine semiconductors other than silicon with CMOS, an obstacle that has been overcome in this work.

The ICFO researchers have shown 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 (QDs). They operated it as a digital camera that is highly sensitive to UV, visible and infrared light at the same time. According to the team, this has never been achieved before with existing imaging sensors. This demonstration of monolithic integration of graphene with CMOS may open the door to a wide range of optoelectronic applications, such as low-power optical data communications and compact and ultra sensitive sensing systems.

The study was carried out by ICFO researchers and led by ICREA Professors Frank Koppens and Gerasimos Konstantatos, in collaboration with 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.

The team explains: "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" ICREA Prof. at ICFO 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".