Opli quotes Nature Photonics paper "Near-unity quantum efficiency of broadband black silicon photodiodes with an induced junction" by Mikko A. Juntunen, Juha Heinonen, Ville Vähänissi, Päivikki Repo, Dileep Valluru & Hele Savin from Aalto University, Espoo, Finland. From the abstract:
"Present-day photodiodes notably suffer from optical losses and generated charge carriers are often lost via recombination. Here, we demonstrate a device with an external quantum efficiency above 96% over the wavelength range 250–950 nm. Instead of a conventional p–n junction, we use negatively charged alumina to form an inversion layer that generates a collecting junction extending to a depth of 30 µm in n-type silicon with bulk resistivity larger than 10 kΩ cm. We enhance the collection efficiency further by nanostructuring the photodiode surface, which results in higher effective charge density and increased charge-carrier concentration in the inversion layer. Additionally, nanostructuring and efficient surface passivation allow for a reliable device response with incident angles up to 70°."
Thanks to TG for the link!