Phonon heat conduction in a semiconductor nanowire

TLDR

The study develops a model for phonon heat conduction in semiconductor nanowires whose dimensions are comparable to the phonon mean free path. The model solves Boltzmann’s equation incorporating confinement‑modified acoustic phonon dispersion and partially diffuse boundary scattering, and is numerically applied to silicon nanowires with varying interface roughness. Phonon confinement and boundary scattering markedly reduce lattice thermal conductivity, with the magnitude and roughness/temperature dependence differing from earlier models, necessitating inclusion of this effect in deep‑submicron device simulations.

Abstract

A model for phonon heat conduction in a semiconductor nanowire with dimensions comparable to the phonon mean free path is developed. It is based on the solution of Boltzmann’s equation, which takes into account (i) modification of the acoustic phonon dispersion due to spatial confinement, and (ii) change in the nonequilibrium phonon distribution due to partially diffuse boundary scattering. Numerical simulation is performed for a silicon nanowire with boundaries characterized by different interface roughness. Phonon confinement and boundary scattering lead to a significant decrease of the lattice thermal conductivity. The value of this decrease and its interface roughness and temperature dependence are different from the predictions of the early models. The observed change in thermal resistance has to be taken into account in simulation of deep-submicron and nanometer-scale devices.