Selective Capture of Hot Electrons/Holes for Plasmon Decay at an Atomically Sharp Metal-Semiconductor Interface

Surface plasmon polaritons (SPPs), enabling to operate electro-magnetic waves at nanometer dimension and femtosecond time scale, provide a favouable bridge of combining the compactness of an electronic circuit with the bandwidth of a photonic network. However, this will require the exploration of effective photon to electron and electron to photon converters. Selectively collecting the non-equilibrium hot electrons/holes generated from SPPs decay at Schottky contacts is a promising approach to achieve on-chip hot-carrier photodetectors. Although there are already many studies on hot electron capturing and a few on hot holes, the mechanism is still under debate. This is mainly because the effect is difficult to study separately from common photo-generation and certain metal-smiconductor combinations can only selectively capture either holes or electrons. In this work, we report a gated Schottky diode device with a plasmonic nano-antenna coupled to the monolithic and atomically sharp aluminum-silicon (Al-Si) heterojunction enabling to capture selectively hot holes and/or electrons. Compared to the noble metals gold or silver, Al features an approximately uniform energy distribution, almost the same lifetime and mean free path for hot electrons and holes. The clear geometric separation of the SPPs source and the energy filtering Schottky diode allow precise investigation of the decay of SPPs and the capture of hot charge carriers. Using scanning photocurrent microscopy analysis, we elucidated the electrostatic potential in the ultrascaled Si channel and the tunable Schottky barrier. Using a sophistically split gate configuration, hot electrons or hot holes can be selectively captured with similar external quantum efficiency, demonstrating experimentally the uniform energy distribution of hot electrons/holes energy for SPPs in Al.