Carrier diffusion in semiconductor nanoscale resonators

It is shown that semiconductor nanoscale resonators with extreme dielectric confinement accelerate the diffusion of electron-hole pairs excited by nonlinear absorption. The response function of the effective carrier density is computed by an efficient eigenmode expansion technique. A few eigenmodes of the diffusion equation effectively capture the long-timescale carrier decay rate, which is advantageous compared to time-domain simulations. Notably, the eigenmode approach elucidates the contribution to carrier diffusion of the in-plane and out-of-plane cavity geometry. These results and insights may be used to optimize the design of various photonic devices, e.g., for applications in all-optical signal processing.