An Efficient Nanophotonic Hot Electron Solar-Blind UV Detector

A solar-blind UV photodetector is designed and fabricated based on a nanophotonic metal-oxide-semiconductor structure. A large potential barrier of similar to 3.8 eV at the metal/oxide interface enables solar-blind UV detection by blocking the electrons excited by visible photons while allowing UV-excited hot electrons to pass through. By selecting metal absorbers with high density of states near the Fermi level and employing photon management in self assembled pseudoperiodic metal nanostructures, we managed to achieve similar to 74% spectrally averaged UV absorption at lambda = 200-300 nm. Furthermore, such a high UV absorption is achieved within the hot electron mean free path of similar to 50 nm from the metal/oxide interface, effectively facilitating the ballistic transport of the UV-excited hot electrons across the interfacial barrier and improving the overall photocurrent. The device has demonstrated a responsivity of 29 mA/W and an internal quantum efficiency of similar to 48% at lambda = 269 nm, a significant advance compared to internal quantum efficiency of existing hot electron photodetectors. The photoresponse to visible light is 3-4 orders lower than the UV responsivity, implementing solar-blind UV detection. These results indicate that photon management in metal absorbers with high density of states near the Fermi level can drastically improve the quantum efficiency of hot electron detectors by >10x compared to existing metal/semiconductor Schottky photodetectors. The same device principle can also be extended to cover other spectral regimes inaccessible to conventional Si-based photodetectors.