Multiscale-multiphysics modeling of nonclassical semiconductor devices

This work describes our on-going efforts to develop a multiscale Quantum Atomistic Device Simulator (QuADS 3-D) where: a) material parameters are obtained atomistically using first-principles, b) structural relaxation and phonon dispersions are studied via molecular mechanics/dynamics, c) a variety of tight-binding models (s, sp3s*, sp3d5s*) are used for the calculation of electronic bandstructure and interband transition rates, and d) coupled charge-phonon transport is simulated using a combined Monte Carlo-NEGF framework. The atom-by-atom simulation capability in QuADS 3-D exposes new degrees-of-freedom at nanoscale (such as engineering the stress, hybrid crystal cuts, composition, surface polarization, and electrostatics) and creates transformative design routes for boosting performance and reliability of novel nanoelectronic devices. Application of QuADS 3-D is demonstrated by four examples: 1) quantum and coulomb effects in nanoscale FETs; 2) correlation of structural modifications and reliability in AlGaN HEMTs; 3) effects of contact resistances in nanostructured thermoelectric coolers; and 4) efficiency droop in nanostructured III-N LEDs.