Abstract

The behaviour of nanoscale devices is strongly affected by the nature and quality of their surface. For instance, in thin nanomembranes the overall electrical conductivity is dominated by the surface conductivity [1]. A similar behaviour occurs also in silicon (Si) photonic nanowaveguides, where the natural termination of the crystal lattice results in the presence of surface states, that absorb photons with energy lower than the bandgap [2]. This process, called surface-state absorption (SSA), generates free carriers at the waveguide core interfaces, and has been used to realize near-infrared all-Si photodetectors [3]. In this work, we show that at the typical optical power level used in linear applications, surface free carrier generation at the core/cladding interface is so massive that the electrical properties of the Si waveguide are dominated its surface.

© 2015 IEEE