Electroluminescence in plasmonic actuator based on Au/SiO₂/n-Si tunnel junction

Abstract A compact electrical source capable of generating surface plasmon polaritons would represent a crucial step for on-chip plasmonic circuitry. The device fabrication of plasmonic actuator based on Au/SiO2/n++Si tunnel junction and performance have been reported in [ACS photonics, 2021, 8, 7, 1951–1960]. This work focuses on the underlying mechanisms of electroluminescence. The n-type Si samples were doped with concentrations ranging from 1.6 × 1015 cm−3 to 1.0 × 1020 cm−3. A low voltage of 1.4 V for intense light emission was achieved at the highest concentration. The electrical/spectral characteristics and energy band diagrams calculation show two distinct behaviors indicating two distinct mechanisms of light emission are at work in the heavily doped versus the lightly doped Si. In the heavily doped case, the light output is correlated to tunneling current and the subsequent conversion of surface plasmons to photons, while that for the lightly doped case is due to indirect band-to-band recombination in silicon. The results are validated by numerical simulation which indicates that the heavy doping of the n++-Si is necessary to achieve surface plasmon generation via electron tunneling due to the presence of band tail states and their effect on lowering the barrier height.