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Abstract: In this work, we report on the design, fabrication, electrical and optical characterization of innovative silicon npn bipolar junction phototransistors, with a finger-shaped emitter implant. Different finger width and interfinger distances, emitter geometries, metal contacts and doping profiles have been implemented to study the impact on the current gain and the spectral responsivity. Such a finger emitter/base junction proved to significantly enhance both the current gain and the responsivity in the blue spectral region with respect to the standard fully implanted detector (maximum current gain of 158 and 72, and responsivity=0.25 and 0.20A/W, respectively). BJTs featuring an additional N-channel implant below the emitter n+-fingers were also successively fabricated and exhibit an improved current gain of 650. The comparison of experimental results for all the implemented geometries allow the identification of the best performing BJT, in terms of current gain and responsivity, and of a figure of merit which takes into account the two fundamental layout parameters affecting the optical and electrical performance: number of emitter fingers and their total perimeter. The new finger-BJTs will be employed as gas sensors after being coated with a metalloporphyrin sensing film, that changes its light absorption properties in the blue when interacting with the gas molecules. A functional measurement campaign has been scheduled with ethanol vapors at different concentrations. [Copyright &y& Elsevier]

In this paper, a new class of H2 sensors made up of mesoscopic polysilicon wires coated by palladium is presented. Using surface micromachining combined with an usual microelectronic planar process, polysilicon wires of the following dimensions have been constructed: from 0.25 up to 3.7 μm wide, from 100 up to 140 μm long, about 600 nm thick. Because of their high surface/volume ratio, these wires have shown a very high resistance percentage variation under hydrogen absorption. Experimental measurements have been performed in 100 ppm H2 flux at room temperature and atmospheric pressure. In order to reach transducers with an enhanced resolution, laser annealing experiments have been performed with the aim of oxidising the polysilicon and obtaining a consequent further reduction of the wire cross-section. [Copyright &y& Elsevier]