An incredible result was achieved thanks to the unique silicon nanostructures that trigger the “process of multiplication of charge carriers”.
Finnish scientists from Aalto University have created a photodetector device with an external quantum efficiency of about 130%. This is the first time that researchers have managed to achieve more than one hundred percent of this indicator. The development paper was published in Physical Review Letters.
“When we saw the results, we could hardly believe our eyes. We immediately wanted to check them with independent measurements, ”says the head of the study, Professor Hele Savin. Experts from the National Metrological Institute Physikalisch-Technische Bundesanstalt were invited for verification, who confirmed that there was no mistake. “This is a major breakthrough – and at the same time, a long-awaited step forward for us, metrologists, who dream of higher sensitivity [of measuring instruments],” said a representative of the Lutz Werner Institute.
External quantum efficiency (IQE) is defined as the ratio of the number of generated pairs of electrons to the number of photons incident on the device. One hundred percent IVE means that one incoming photon generates one electron for the electrical circuit of the device. The photodetector developed by Finnish physicists has an average of 1.3 electrons per photon.
The secret of this result lies in the unique silicon nanostructures that trigger the “process of multiplication of charge carriers.” This phenomenon has not been observed previously in real devices, since electrical and optical losses reduced the number of generated electrons and decreased the IQE index. In the new photodetector, losses were reduced to almost zero.
Such results make it possible to improve the efficiency of almost any device based on detection and registration of light flux: unmanned vehicles, mobile phone cameras, tracking devices. “Such detectors are attracting more and more attention, especially in the field of biotechnology and monitoring of industrial processes,” summarize the authors of the development.