Abstract
Silicon nanowires (SiNWs) exhibit unique optoelectronic properties originating from one-dimensional confinement effect. Technologically relevant properties—including band gap, radiative and nonradiative transitions, and charge carrier relaxation rates—are influenced by sampling of momentum along the growth direction. In this work, we quantify the influence of momentum dispersion on hot-electron relaxation rates and nonradiative lifetimes for SiNWs with ⟨100⟩ and ⟨111⟩ growth directions. Specifically, we account for nonradiative transitions between electronic states with different momentum, where changes in energy and momentum are achieved via interaction with a thermal bath of nuclear degrees of freedom. Photoexcited dynamic processes in reference SiNWs are computed via “on-the-fly” nonadiabatic couplings between electronic and nuclear degrees of freedom based on density functional theory (DFT). The dynamics of electronic degrees of freedom is propagated by a Redfield equation of motion for the reduced density matrix. Our results show that transitions allowing change of momentum prompt electron relaxation faster than those not allowing change of momentum. Our study also indicates that the electron relaxation time in ⟨100⟩ SiNW is longer than that in ⟨111⟩ SiNW.