The 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, according to IFCO (Barcelona, Spain). The use of 2D materials such as graphene within CMOS could provide benefits in hyperspectral imaging systems covering visible, infrared and terahertz frequencies.
The research team created a CMOS image sensor with 388 by 288 pixels on a die measuring 15.1mm by 14.3mm that detects light over optical wavelengths from 300nm to 2,000nm.
The graphene-QD image sensor was fabricated by taking lead-sulphide colloidal quantum dots, depositing them onto the chemically vapor deposited graphene and subsequently depositing this hybrid system onto a CMOS wafer with image sensor pixels and a read-out circuit.
"No complex material processing or growth processes were required to achieve this graphene-quantum dot CMOS image sensor," said Stijn Goossens, one of the researchers, in a statement issued by ICFO. "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," he said.
The extension of the quantum dots to cover short infrared wavelengths from 1,100nm to 1,900nm enables detection of the night glow of the atmosphere under a dark and clear sky enabling passive night vision imaging, according to researcher co-leader Professor Gerasimos Konstantatos.
"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," Professor Konstantos said in the same statement.
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