Thanks to silicon and complementary metal-oxide semiconductors (CMOS) technology, microelectronics has progressed greatly in the last four decades, thereby making possible computing, compact and economical digital cameras, smartphones, as well as a majority of the electronic gadgets people depend on at present.
However, the diversification of this platform into applications other than visible light cameras and microcircuits has been obstructed by the difficulty to integrate semiconductors other than silicon with CMOS.
This hurdle has now been sorted. ICFO researchers have demonstrated for the first time the monolithic incorporation of a CMOS-integrated circuit with graphene, resulting in a high-resolution image sensor comprising of numerous photodetectors based on graphene and quantum dots (QD). They worked it as a digital camera that is extremely sensitive to visible, UV, and infrared light at the same time. This has never been accomplished before with currently available imaging sensors. Overall, this demonstration of monolithic integration of graphene with CMOS enables an extensive range of optoelectronic applications, such as compact and ultra-sensitive sensing systems and low-power optical data communications.
The research was published in Nature Photonics, and showcased on the front cover image. The research was conducted by ICFO researchers Stijn Goossens, Gabriele Navickaite, Carles Monasterio, Schuchi Gupta, Juan Jose Piqueras, Raul Perez, Gregory Burwell, Ivan Nitkitsky, Tania Lasanta, Teresa Galan, Eric Puma, and led by ICREA Professors Frank Koppens and Gerasimos Konstantatos, along with the company Graphenea. The graphene-QD image sensor was produced by taking PbS colloidal quantum dots, placing them onto the CVD graphene and then depositing this hybrid system onto a CMOS wafer with image sensor dies and a read-out circuit.
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.
Stijn Goossens, Researcher, ICFO
As ICREA Prof. at ICFO Gerasimos Konstantatos, expert in quantum dot-graphene research states, “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 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.
Professor Frank Koppens, ICREA, ICFO
This research project is presently incubating in ICFO’s Launchpad. The team is working along with the institute’s tech transfer professionals to promote this breakthrough together with its full patent portfolio of imaging and sensing technologies to the market.
This research has been partly supported by the European Graphene Flagship, the European Research Council, the Government of Catalonia, Fundació Cellex and the Severo Ochoa Excellence program of the Government of Spain.