https://cdn.specpick.com/images/photonics/graphene_cmos.jpg712370

Currently, silicon-based CMOS technology is one of the most important parameter of the growing electronics world. However, to continue the path of progress in the electronics industry new technology must be developed with the ability to integrate CMOS with other semiconductors. The Graphene Flagship, EU's largest research initiative with a €1 billion budget, is one such project which aims at taking graphene from laboratories into the market.

Under the same research inititative, a team of researchers from  ICFO, the Institute of Photonic Sciences in Barcelona, now, have shown that it is possible to integrate graphene into a CMOS integrated circuit. According to the work report published in the Nature journal, the team combined the graphene-CMOS device with quantum dots to create an array of photodetectors, which produce a high resolution image sensor. When used as a digital camera this device was able to simultaneously sense UV, visible and infrared light. The scientists claim that this is just one example of how the device might be used, while other possible applications may include microelectronics, sensor arrays and low-power photonics. The development of this monolithic CMOS-based image sensor represents a milestone for low-cost, high-resolution broadband and hyperspectral imaging systems which further can enable graphene-CMOS technology for a vast amount of applications ranging 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.

The results were enabled by the collaboration between Graphene Flagship partner Graphenea (a Spanish graphene supplier) and ICFO, within the optoelectronics work-package of the Graphene Flagship. By creating a hybrid graphene and quantum dot system on a CMOS wafer using a layering and patterning approach, the Flagship team solved a complex problem with a simple solution: first, depositing the graphene, then patterning it to define the pixel shape and finally adding a layer of PbS colloidal quantum dots.

The photoresponse of the system is based on a photogating effect, which starts as the quantum dot layer absorbs light and transfers it as photo-generated holes or electrons to the graphene, where they circulate due to a bias voltage applied between two pixel contacts. The photo signal is then sensed by the change in conductivity of the graphene, with graphene’s high charge mobility allowing for the high sensitivity of the device.

According to the researchers, 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.

The commercial applications of the research and the potential for imaging and sensing technology are now being explored in ICFO’s Launchpad incubator. The integration of graphene with CMOS technology is a cornerstone for the future implementation of graphene into consumer electronics. With the work clearly demonstrating the feasibility of the approach and the significant investment by the Graphene Flagship in the system level integration of graphene, the technology is being seen to grow along the innovation roadmap of the future soon.