Nonlinear carrier dynamics in silicon nano-waveguides

TL;DR

This paper investigates the complex, nonlinear carrier recombination dynamics in silicon nano-waveguides through experiments and theory, revealing density-dependent lifetimes and trapping effects that influence device performance.

Contribution

It provides the first detailed analysis of nonlinear, trap-assisted recombination dynamics in silicon nano-waveguides, combining experimental results with theoretical modeling.

Findings

Carrier lifetime varies from 800 ps to 300 ns during recombination.

Trapping effects cause decay curves to depend on initial carrier density.

High carrier densities lead to faster recombination rates.

Abstract

Carrier recombination dynamics in strip silicon nano-waveguides is analyzed through time-resolved pump-and-probe experiments, revealing a complex recombination dynamics at densities ranging from ${10^{14}}$ to ${10^{17}}\,$cm$^{{-3}}$. Our results show that the carrier lifetime varies as recombination evolves, with faster decay rates at the initial stages (with lifetime of ${\sim 800}\,$ps), and much slower lifetimes at later stages (up to ${\sim 300}\,$ns). We also observe experimentally the effect of trapping, manifesting as a decay curve highly dependent on the initial carrier density. We further demonstrate that operating at high carrier density can lead to faster recombination rates. Finally, we present a theoretical discussion based on trap-assisted recombination statistics applied to nano-waveguides. Our results can impact the dynamics of several nonlinear nanophotonic devices in which free-carriers play a critical role, and open further opportunities to enhance the performance of all-optical silicon-based devices based on carrier recombination engineering.