Quantum efficiency of black silicon photodiodes at VUV wavelengths

Black silicon (b-Si) is an emerging material made by modifying silicon with nanostructures for improved photon detection. It has been demonstrated that when used in photodetectors b-Si significantly improves photon detection and extends spectral sensitivity from NIR to the visible wavelengths. However, no data have been reported in the Vacuum Ultraviolet (VUV) range, which is increasingly becoming important for many applications. Here, we have measured the spectral response of n-type b-Si light-trapping photodiodes under VUV radiation at ambient and cryogenic temperatures. The device exhibited a near-unity quantum efficiency above the 1.1 eV intrinsic bandgap of silicon. Quantum efficiency increased linearly with photon energy above the electron-hole pair creation energy of silicon ∼3.6 eV and the device had a responsivity of 0.2 A/W at 175 nm at room temperature in vacuum. These results demonstrate new technology in UV detection and could pave way for the development of a high quantum efficiency black silicon photomultiplier device (b-SiPM) needed for direct VUV photon detection in noble gas and liquid scintillating detectors.