Electrical-Driven Plasmon Source of Silicon Based on Quantum Tunneling

A silicon-based light source presents an unreached goal in the field of photonics due to silicon's indirect electronic band structure preventing direct carrier recombination and subsequent photon emission. Here, we utilize inelastically tunneling electrons to demonstrate an electrically driven light emitting silicon-based tunnel junction operating at room temperature. We show that such a junction is a source for plasmons driven by the electrical tunnel current. We find that the emission spectrum is not given by the quantum condition where the emission frequency would be proportional to the applied voltage, but the spectrum is determined by the spectral overlap between the energy-dependent tunnel current and the modal dispersion of the plasmon. By coupling an internal electric field enhancement with an external k-vector matching grating, we were able to demonstrate a 10-fold increase in the internal efficiency and a 40-fold increase in overall quantum efficiency. Such an electron tunneling-based mechanism could lead to a new class of solid-state light sources with unique features such as down-scalability and temporal responses that are significantly shorter than that of light-emitting diodes.