Surface Plasmon Polaritons Propagation Through a Schottky Junction: Influence of The Inversion Layer

Surface plasmon polaritons (SPPs) originate from resonance coupling between surface-bound electrons and photons on interfaces with specific material properties. Unfortunately, owing to the existence of SPPs on an interface, its reach is plagued by intrinsic dissipative losses in the materials making up the interface, severely restricting the application domain. One way to reduce the propagation losses is to use distributed electrical injection across the interface to create a population inversion to provide energy to the decaying SPP wave. A promising technique is to use a Schottky junction formed between a semiconductor and a metal because such an interface can sustain a population inversion under electrical injection. We previously analyzed the plasmonic dispersion relation for such a device when biased. Here, we extend that analysis to consider the influence of the inversion layer when minority carriers are injected from an external electrical source. In particular, we derive analytical expressions for the loss reduction and associated gain spectrum broadening, taking into account the doping concentration in the semiconductor and the externally applied voltage across the junction. Our analysis gives vital information for the design and utilization of Schottky junction interfaces as active waveguides for routing SPPs in integrated circuitry.