Localization And Manipulation Of Surface Plasmon Polariton Based On Electron Accumulation In Metal-Oxide-Semiconductor Structure

Surface plasmon polaritons(SPPs)are electronmagnetic waves that travel along an interface between materials with positive and negative dielectric constants(e.g.a metal–dielectric interface).SPP modes can be applied in localizing and manipulating electromagnet field in a small area at sub-wavelength scale.However,tradeoff between strong field confinement or small loss in metal/dielectric SPP and its lack of controllability impose restriction in further application of such SPP devices.By forming an accumulation layer inside semiconductor material of a metal-oxide-semiconductor(MOS)structure,inside semiconductor area there is a dielectric constant distribution changing gradiently from negative to positive and therefore a interface where the dielectric constant is zero.This structure not only enables us to realize sub-wavelength scale filed confinement of SPP but also control the field by manipulating the carrier distribution in semiconductor at wavelength between 2 to 20 micrometers.In this article,we will present analysis of Ag/Hf O2/N-Ga As MOS in aspects of both electron distribution and electromagnetic field distribution.The main contents of this paper as follows:(1)Electron density distribution of a Ag/Hf O2/N-Ga As planar MOS structure under accumulation status is calculated based on Poisson equation.From electron density distribution,the distribution of complex permittivity of said structure is achieved using Drude-Lorentz model.Then we analyze how factors like gate voltage,the oxide thickness and doping concentration influence the distribution of carriers and permittivity.(2)A mode analysis is performed on the planar MOS structure under accumulation,showing that two modes can be supported by the structure.We then look into why these modes exist and how their field distribute.The dispersion curve,propagation length and mode area of two modes are studied,as well as the effect of manipulation through gate voltage,the oxide thickness and doping concentration.(3)Two designs of 2D MOS structure,including a semiconductor ridge and a metal strip structure,are presented and mode analyzed.An explanation of multiple high order modes and their voltage dependence is proposed.The dispersion curve,propagation length and mode area of SPP modes in these 2D MOS structures are studied,and then compared with modes under zero gate voltage.