The Short-Wave Infrared (SWIR) spectrum reveals distinct optical properties of many materials which considerably differ from their properties in the visible spectrum, creating unique imaging opportunities. SWIR imaging is usually done with InGaAs focal plane arrays which due to their low-volume manufacturing and high price remain inaccessible for many applications. Image sensors based on Colloidal Quantum Dot (CQD) photodiodes recently emerged as alternative that has a potential to enable high-volume manufacturing of SWIR image sensors. Multiple images in distinct SWIR bands often need to be captured, but due to the unique properties of CQD photodiodes, it is challenging to directly integrate optical filters on top of them for the purposes of spectral imaging. Here, we propose a strategy to overcome these challenges by integrating CQD photodiodes on top of optical metasurfaces. Patterned silicon nanostructures enable detection of spectrally and polarization sensitive SWIR light. The proposed device stack is compatible with thin-film processing and demonstrates a path towards affordable spectral imaging in SWIR which can impact many industrial, scientific and consumer domains.
In this paper, we present thin-film photodetector (TFPD) image sensors for the short-wave infrared (SWIR) range. Monolithic integration of quantum dot (QD) absorbers enables quantum efficiency of 70% at 1400 nm and pixel pitch below 2 μm. We present image sensors on custom CMOS readout fabricated using 130 nm node. We review latest advancements on the photodiode stack and the pixel engine, including the thin-film pinned photodiode architecture. Furthermore, we study the manufacturing flows to realize full wafer capability for volume processing. QD image sensors are paving the way to add augmented vision into future XR systems with extra functionalities.
We present a near-infrared (NIR) imager based on high-performance organic photodiode in terms of dark current, specific detectivity and response time. A carefully designed interfacial layer is introduced in the thin-film organic photodiode stack to reduce trap assisted carrier emission leading to sub-nA/cm2 dark current and external quantum efficiency above 50% in the NIR range. The developed imager chip benefits from this improved dark current-voltage characteristic (high light signal to dark noise ratio) and enables high-resolution, monolithic NIR image sensors.
Hyperspectral and multispectral imaging enable augmented reality experience by collecting spectral information of a scene and mapping it onto a 2D image. This imaging method is especially powerful if done in short-wave infrared (SWIR) because of the unique spectral fingerprints of many molecules found in this region of the spectrum. Despite its high potential, this technology has not been widely adopted due to the high price of standard SWIR cameras. Recently, image sensors based on colloidal quantum dot thin films have gained a lot of attention due to their potential to enable affordable and high-resolution SWIR imaging. In this work, we present the latest results of our efforts to leverage imec's thin-film SWIR imaging platform for spectral imaging. We present the measurement results of our multispectral photodetectors, as well as the results of optical simulations demonstrating new concepts for light filtering in the SWIR region, compatible with the thin-film technology.
In this work, we present a photodetector based on PbS colloidal quantum dots which can be used for low-cost, high-resolution multispectral imaging in the short-wavelength infrared range. Using versatile solution-based processing of thin films, we fabricated a switchable, dual-channel, two-terminal photodetector that can be monolithically integrated with small-pitch CMOS readout arrays. Its vertically stacked structure provides higher spatial resolution compared to conventional snapshot multispectral image sensors. We show the results of the optical simulations based on the transfer matrix method, which allowed us to achieve a wavelength-tunable narrowband response. We demonstrate the operation of the photodetector and its facile tunability by showing an EQE of more than 25% at different bands in the wavelength range of 1-1.5 μm. This work demonstrates the potential of the emerging thin-film technology for multispectral imaging.
In this paper, we present short-wave infrared (SWIR) image sensors with high pixel density. Quantum dot (QD) photodiode stack is monolithically integrated on custom, 130 nm node CMOS readout circuit. State-of-the-art pixel pitch of 1.82 μm is demonstrated in focal plane arrays sensitive at eye-safe region above 1400 nm wavelength. Thin-film photodiode (TFPD) technology will facilitate realization of ultra-compact SWIR sensors for future XR applications, including eye-safe tracking systems and enhanced vision.
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