Polarizability of a Semiconductor Nanoparticle as a Generalized Network Function

Surface plasmon resonance in semiconductors occurs in the terahertz frequency range, enabling semiconductor nanoparticles to take up the roles in supporting the development of sensors and circuit components in this part of the electromagnetic spectrum. Owing to the lower concentration of charge carriers in semiconductors, field penetration into a semiconductor is more pronounced than that in a metal. As a result, space-charge effects have a stronger influence on plasmonic interactions within a semiconductor. By coupling the moments of the Boltzmann's equation to the field intensities from the Maxwell's equations, polarization induced by an applied terahertz electric field on a semiconductor nanoparticle is obtained by noting the charge density along with the interior field and current distributions. Change in the patterns of the interior field and charge distribution as the frequency of the applied field is increased indicates an evolution of plasmonic interaction from surface to bulk phenomena. A comprehensive discussion of the relationship between the key parameters such as skin depth, Debye length, and bulk plasma frequency to the charge distribution, current distribution and the surface plasmon resonance frequency are presented with results of computations based on charge-field interactions. Equivalent circuits for semiconductor nanoparticles can be constructed from consideration of the dynamics of charge motion to provide efficient estimation of the induced dipole moment on the nanoparticle. The polarizability of a semiconductor nanoparticle can be interpreted as a generalized network function, owing to its close relation to the admittance of the equivalent circuit.