Quantum transport beyond the ballistic limit

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This thesis extends an existing full-band and atomistic quantum transport simulator using the nonequilibrium Green’s function (NEGF) formalism to model fully coupled electron-phonon transport. The approach computes and investigates the electrothermal properties of nanoscale devices. The semi-empirical sp3d5s∗ tight-binding (TB) method models electron properties, while lattice oscillations (phonons) are described using the valence-force-field (VFF) formalism. Both methods accurately reproduce bulk dispersion relations across various materials, allowing for atomistic resolution and straightforward extension to nanostructures. Full-band and atomistic quantum transport models are crucial for capturing quantum mechanical effects and atomic granularity in novel nanoelectronic devices. However, these approaches are computationally demanding, particularly with electron-phonon scattering, necessitating physical and numerical approximations for feasibility. These approximations are validated by calculating phonon-limited low-field mobility in various semiconductors and comparing results with the linearized Boltzmann transport equation. The thesis further explores fully coupled electron-phonon transport simulations in the NEGF framework, deriving and discussing the necessary scattering self-energies. These energies drive electron and phonon populations out of equilibrium, leading to local lattice temperature variations and self-heating e