Graphene for Short-wave infrared (SWIR) cameras

Short-wave infrared (SWIR) light is a portion of the infrared spectrum between the near-infrared and mid-wave infrared. SWIR can be very useful in applications such as nighttime imaging, agriculture monitoring, or food inspection. For this reason, the projected market size for SWIR cameras is more than $400 million for 2027.

Image: Food bruising detection with SWIR. Source: RJ Wilson.

In this band, vegetation has a different color than soils, which between themselves appear as dark to light brown, depending on the soil type. Urban areas also have a distinct color, as do snow, ice, and clouds. Cameras based on SWIR can make a distinction between hardwood and coniferous trees, or densely and lightly populated urban areas. The technology can also be used to classify different types of rock formations, as well as heat emitted from surfaces.

Image: SWIR cameras see through fog. Source: NASA.

SWIR also finds a use in quality inspection of semiconductor wafers and die. Wafers and chips made of silicon are transparent to SWIR light. Frontside or backside illumination of the silicon-based devices with infrared lighting enables imaging of wafer alignment marks, particles, micro-cracks, and other fine features. The technology is also used in various production processes, such as hot glass and molten metal inspection.

Image: Silicon wafer inspection. Source: RJ Wilson.

Currently, Indium Gallium Arsenide (InGaAs) is most commonly used to make SWIR detectors. The ultimate challenge for a wider application of SWIR imaging products is the high cost of InGaAs-based SWIR detectors. A SWIR camera on the market today costs more than $10,000, more commonly near the $20,000 mark. The high price is related to the complex manufacturing of InGaAs that also prevents increase of the detector production volumes. Clearly, new materials are needed for this highly prized application.

The Graphene Flagship has made GBIRCAM one of its Spearhead projects, selecting graphene-based SWIR cameras among the most prospective applications of graphene in the near future. Using one super-pixel device from graphene, that has a broad spectral resolution, reduces the cost of broad spectrum imaging compared to using several different sensors or cameras, making this technology more accessible to businesses, not only for sensor integration in products, but also from an end-user perspective.

The final broadband camera product, that includes the SWIR spectrum, using a single detector array, is set to perform in an operational environment at a pre-commercial scale by the end of the three-year project. By this point, the single focal plane array of multielement graphene superpixels will be implemented on a bespoke read-out integrated circuit (ROIC), integrated with the necessary lens system, mechanical housing and software.

Image: Graphene-based broadband camera. Credit: Graphene Flagship.

In parallel, a European Innovation Council Fast Track to Innovation (FTI) project was directed at developing the market adoption of the G-IMAGER, a graphene imager based on graphene-on-wafer technology. The G-Imager is a short-wave infrared (SWIR) detector for applications in semiconductor inspection, sorting systems, spectroscopy hyperspectral imaging and surveillance. In this solution, graphene is used as a charge transducing layer.

Image: Emberion’s linear array sensor covering the VIS-SWIR spectral range.

During that project, which is led by Emberion Oy, we embarked on a course to construct and market the G-Imager which will bring the core price down significantly, allowing market volumes to multiply manyfold. The main efforts that will lead to industrial adoption of G-IMAGER technology are in scaling graphene and imager wafer production capacities to more than 10,000 wafers/year, to increase process yield and implement automated and optimized quality control on a customized rapid prototyping line, within the Graphenea Foundry.

Others are also developing graphene-based SWIR sensors, such as the Spanish spin-off Qurv Technologies that targets applications in autonomous driving. That technology relies on the interaction of graphene with semiconductor quantum dots, integrated with machine vision to provide vehicles with more information about their surroundings than they could get with any other technology.

With so many developments, it is expected that sooner rather than later graphene-based SWIR cameras will be at disposal to a wide range of markets, from food inspection to autonomous driving.