Light Detector With Record-High Sensitivity

Structure of the novel photodetector: Alumina-coated nanostructures are located on top of a high-resistivity n-type silicon substrate. (Source: U Aalto)

Structure of the novel photodetector: Alumina-coated nanostructures are located on top of a high-resistivity n-type silicon substrate. (Source: U Aalto)

The research team led by Hele Savin has developed a new light detector that can capture more than 96 percent of the photons covering visible, ultraviolet and infrared wavelengths. “Present-day light detectors suffer from severe reflec­tion losses as currently used anti­reflection coatings are limited to specific wave­lengths and a fixed angle of incidence. Our detector captures light without such limitations by taking advantage of a nano­structured surface. Low incident angle is useful especially in scin­tillating x-ray sensors”, Savin explains.

“We also addressed electrical losses present in traditional sensors that utilize semi­conductor pn-junctions for light collection. Our detector does not need any dopants to collect light – instead we use an inversion layer generated by atomic layer deposited thin film.” The new concept for light detection kindled from the team’s earlier research on nano­structured solar cells. Indeed, the nano­structure used in the light detector is similar to that used by the team a couple of years ago in their record-high efficiency black silicon solar cells.

The team has filed a patent appli­cation for the new light detector. The proto­type detectors are currently being tested in imaging appli­cations related to medicine and safety. The team is also conti­nuously seeking new appli­cations for their invention, especially among the ultra­violet and infrared ranges that would benefit from the superior spectral response. (Source: Aalto U)

Reference: M. A. Juntunen et al.: Near-unity quantum efficiency of broadband black silicon photodiodes with an induced junction, Nat. Phot., online 14 November 2016; DOI: 10.1038/nphoton.2016.226

Links: Dept. of Micro and Nanosciences, Aalto University, Espoo, Finland

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