Graphene-based camera can image invisible light

Spanish researchers have developed a CMOS integrated camera consisting of hundreds of thousands of photodetectors based on graphene and quantum dots (QD). Described in the journal Nature Photonics, their invention is capable of imaging visible and infrared light at the same time.

Over the past 40 years, microelectronics has advanced thanks to silicon and CMOS (complementary metal-oxide semiconductors) technology, making possible computing, smartphones, compact digital cameras and more. 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 by researchers at Spain’s Institute of Photonic Sciences (ICFO), working in collaboration with graphene producer Graphenea.

The team has demonstrated the monolithic integration of a CMOS integrated circuit with graphene, resulting in a high-resolution image sensor. The 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.

“No complex material processing or growth processes were required to achieve this graphene-quantum dot CMOS image sensor,” said study co-author Stijn Goossens. “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.”

The team operated their device as a digital camera that is highly sensitive to UV, visible and infrared light at the same time — a breakthrough that has never been achieved before with existing imaging sensors. As explained by co-author Professor Gerasimos Konstantatos, “We engineered the QDs to extend to the short infrared range of the spectrum (1100–1900 nm), 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 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 ultrasensitive sensing systems. According to corresponding author Professor Frank Koppens, “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.”

The team is working with ICFO’s tech transfer professionals to bring this breakthrough along with its full patent portfolio of imaging and sensing technologies to the market.

Image caption: Graphene-quantum dots-CMOS-based sensor for ultraviolet, visible and infrared. Image credit: ICFO/D Bartolome.