The optical properties of luminescent Ti-catalyzed Si nanowires are analyzed using continuous-wave and time-resolved photoluminescence (PL) spectroscopy at excitation intensities $\left(I_{\text{ex}}\right)$ above $1\text{W}/{\text{cm}}^2$. At these pump intensities, the PL intensity tends to saturate and the PL decay rate decreases with increasing $I_{\text{ex}}$. These results can be described within the construct of a quasi-two-level rate-equation model that allows for exciton-exciton Auger recombination. Analysis shows that the room-temperature Auger coefficient $\left(C_a\right)$, and thus, the Auger rate is roughly two orders of magnitude less than those estimated for silicon nanoparticles in an oxide matrix. The temperature dependence of the Auger process in the nanowires resembles bulk Si, in which Auger processes are phonon assisted. This work provides valuable quantitative information on one of the key nonradiative processes limiting optical gain from Si nanostructures and could prove important in the design of a Si-based laser.

• Received 25 January 2008

DOI:https://doi.org/10.1103/PhysRevB.78.235422