Ultrahigh responsivity visible and infrared detection using silicon nanowire phototransistors.

Nanowire photodetectors can perform exceptionally well due to their unique properties arising from the nanowire geometry. Here we report on the phenomenal responsivity and extended spectral range of scalable, vertically etched, silicon nanowire photodetector arrays defined by nanoimprint lithography. The high internal gain in these devices allows for detection at below room temperatures of subfemtowatt per micrometer visible illumination and picowatt infrared illumination resulting from band to surface state generation.

Nanowire photodetectors.

The use of nanowires and nanowire structures as photodetectors is an emerging research topic. Despite the large amount of reports on nanowire photoresponse that appeared in the literature over the last decade, the mechanism leading to high photosensitivity and photoconductive gain in high aspect ratio nanostructures has been elucidated only recently. Novel device architectures integrated in single nanowire devices are also being actively studied and developed. In this article, the general nanowire photodetector concepts are reviewed, together with a detailed description of the physical phenomena occurring in nanowire photoconductors and phototransistors, with some examples from recent experimental results obtained in our groups. An outlook on future directions toward the use of semiconductor nanowire photoconductors as intrachip interconnects, single-photon detectors, and image sensors, is also given.