Light detection is a fundamental process lying in the foundation of optoelectronics. The research and application of photodetectors promote the progress and development of our society. The role of photodetectors is to convert radiant energy into electrical output signals, current or voltage. Modern solid-state PDs rely on a range of materials and/or technologies such as Si (0.3-1.1µm wavelengths range), Ge (0.5-1.8µm), InGaAs (0.7-1.7µm), narrow-gap semiconductors InSb (2-6µm), PbS (1-3.6µm), PbSe (1.5-5.8 µm) and HgCdTe (2-16µm), each of them optimized for a specific spectral range with a limited prospect for integration between different platforms. The operation principle of solid-state (semiconductor, SC) PDs is governed by the photoelectric effect, where optical absorption of quanta of light (i.e. a photon) generates free carriers (FCs), electrons and holes via band-to-band (or defect-assisted) transition over the energy bandgap or sub-bandgap potential barrier. The FCs can drift in the electric field and/or diffuse along a temperature (or concentration) gradient to produce a photovoltage response across the output terminals or photocurrent flow in an external circuit.
An extreme diversity of modern multi- and hyperspectral imaging applications, ranging from remote healthcare and environmental monitoring, gas sensing and hazard detection, food and water inspection to biosensing and automotive, share similar urgent needs for high-performance, miniaturized, and lightweight multispectral optical sensors monolithically integrated with low-cost and high-functionality silicon electronics. However, current semiconductor PDs technologies are mainly tailored and optimized to specific spectral bands, and their roadmaps have so far prevented the development of a universal solution for multispectral detectors that could simultaneously address broadband operation spanning from visible to mid-infrared wavelengths. Quite the opposite, different PDs technologies have become so specialized for their band of operation that no viable avenue exists to integrate current state-of-the-art solutions. Thus, there is a pressing need for a radically new approach that could combine high-performance broadband PDs for all spectral bands in one single silicon-based technological platform. Graphene and 2D materials integration with silicon technology opens an unprecedented opportunity to reach this goal, leveraging unique ultra-broadband absorption properties of graphene and the diversity of the 2D family with mature silicon fabrication facilities for scalable and cost-effective monolithic integration with modern read-out electronics and integrated circuits. The project's grand challenge is to radically expand the photodetection capabilities of silicon technology far beyond the visible (VIS) spectrum covering multiple spectral bands, including the infrared (IR), with an ultimate goal of demonstrating that 2D/Silicon integration can represent the long-sought one single technology for a multispectral photodetection at room-temperature outperforming the state-of-the-art solutions.
The proposed research's ultimate goal is to develop novel approaches for multispectral optical detection in emerging 2D hybrid-silicon technology and unify high-performance photodetectors operating in all spectral bands from visible to mid-infrared in one single technological platform. To tackle this highly multidisciplinary research program, the project proposes theoretical and experimental studies of new concepts and physical phenomena for multispectral photodetection in integrated 2D/Silicon hybrids, aiming for innovative solutions, novel device architectures, and disruptive technological development of silicon-based multi- and hyperspectral photodetection systems-on-chip.
