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Waste material classification is critical for efficient recycling and waste management. This study proposes a novel, low-cost material classification system based on a single, voltage-tunable Ge-on-Si photodetector operating across the visible and short-wave infrared (SWIR) spectral regions. Thanks to its tunability, the sensor is able to extract spectral information, and the system effectively distinguishes between seven different materials, including plastics, aluminum, glass, and paper. The system operates with a broadband illuminator, and material identification is obtained through the processing of the photocurrent signal at different bias voltages with classification algorithms. Here, we demonstrate the basic system functionality and near real-time classification of different waste materials. [ABSTRACT FROM AUTHOR]

Energy harvesting is gaining substantial relevance in the realm of ultra-low-power electronics and Internet-of-Things devices with limited access to classic power sources. Several harvesting approaches are available, depending on the energy source; among them, photovoltaic devices benefit from the highest energy density. However, the inclusion of a dedicated photovoltaic cell in a low-power system may result in increased costs and complexity, thus hampering economic sustainability. Conversely, electronic apparatuses often make use of light-emitting-diodes (LEDs), which could be effectively employed as photovoltaic energy harvesters whenever not actively generating photons. Here, we explore the potentials of commercially available LEDs for energy harvesting and determine their quantum efficiency. We examine the correlation of the latter with the spectral response and the available light, demonstrating that visible-wavelength diode emitters can yield very high conversions in the photovoltaic mode. We report measured quantum efficiencies as high as 39% under low-intensity (100 µW/cm2) fluorescent illumination. [ABSTRACT FROM AUTHOR]

A new study investigates the integration of high performance Ge p-i-n and n-i-p heterojunction photodiodes on Si.

Research on germanium-on-silicon near-infrared photodetectors is presented. Findings include the superiority of polycrystaline-germanium evaporation on silicon, which realizes highly efficient photodiodes with improved sensitivity and speed.

Photodetectors based on a Ge-on-Si platform were widely studied over the last two decades, rapidly becoming the technology of choice for CMOS-integrated optoelectronic systems operating in the near infrared. Recently, we demonstrated a proof-of-concept device realized with a back-to-back, Ge-on-Si double photodiode with dual-band optical sensitivity and voltage-tunability characteristics. Such a device represents the cornerstone for the development of integrated imaging systems operating both in the visible and in the near infrared spectral ranges. To achieve this ambitious goal, however, several technology improvements are needed starting from the fabrication of a multipixel array of dual-band photodetectors. Moreover, given the peculiar electronic behavior of the proposed device, specific readout electronics must be developed and integrated onto a CMOS platform. In this paper we demonstrate the operation of a Ge-on-Si multipixel array with a custom-developed readout integrated chip. We show a complete system characterization, also demonstrating its imaging capabilities with a simple experiment for the determination of the intensity profile of two different laser beams. [ABSTRACT FROM AUTHOR]