Phonon effect on single-electron transport in two-dot semiconductor devices

Abstract

We have studied the single-electron transport in silicon nanocrystal (NC)-based structures using Monte Carlo simulation including the coupling between two dots. This coupling has been modeled by taking the collisional broadening of energy levels in the dots into account through the spectral function associated with the electron-phonon interaction. The first stage of the calculation is the determination of the phonon spectra in the dots using the adiabatic bond charge model adapted to the case of silicon NCs. A self-consistent Schrödinger–Poisson solver is then used to calculate the electronic structure of the NCs according to the applied bias. The tunneling rates between broadened levels are calculated within the perturbation theory from a tunneling Hamiltonian and introduced in a Monte Carlo algorithm to treat the sequential transport of electrons. We have studied structures consisting of two Si NCs embedded in silicon oxide and two metallic contacts for different parameters as the temperature and the barrier widths. The resulting I-V characteristics exhibit a sharp peak with lateral lobes due to phonon-assisted tunneling. These lobes are strongly influenced by the vibrational surface states.