Graphene instead of silicon has been used for a CMOS integrated circuit, resulting in a high-resolution image sensor consisting of hundreds of thousands of photodetectors based on graphene and quantum dots (QDs). This graphene-QD CMOS sensor can be operated as a digital camera that is highly sensitive to light in the UV, visible and IR wavelengths (300 to 2000 nm). The sensor could enable a wide range of optoelectronic applications, such as low-power optical data communications and compact and ultra-sensitive sensing systems. Graphene-quantum dots-CMOS-based sensor for ultraviolet, visible and infrared. Courtesy of ICFO/ D. Bartolome. To create the novel sensor researchers at the Institute of Photonic Sciences (ICFO) took lead sulphide (PbS) colloidal quantum dots (CQDs) and deposited them onto chemical vapor deposition (CVD) graphene. This hybrid system was then put on 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 researcher 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 graphene-CMOS integration demonstrated by the researchers could be useful for incorporating 2D materials into next-generation microelectronics, sensor arrays, low-power integrated photonics and CMOS imaging systems covering visible, IR and THz frequencies. “We engineered the QDs to extend to the short infrared range of the spectrum (1100 to 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 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,” said professor Gerasimos Konstantatos. The team is working with ICFO’s tech transfer professionals to bring its discovery to market. “The development of this monolithic CMOS-based image sensor represents a milestone for low-cost, high-resolution broadband and hyperspectral imaging systems,” professor Frank Koppens said. “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.” The research was published in Nature Photonics (doi:10.1038/nphoton.2017.75). ICFO researchers have developed the first graphene — quantum dots — CMOS integrated based camera, capable of imaging visible and infrared light at the same time. The camera will be useful for many applications that include night vision, food inspection, fire control, vision under extreme weather conditions, to name a few. The imaging system is based on the first monolithic integration of graphene and quantum dot photodetectors with a CMOS read-out integrated circuit. It has proven to be easy and cheap to fabricate at room temperature and under ambient conditions, allowing for low-cost mass-production. Courtesy of ICFO.
