We present a calculation of the lattice thermal conductivity of Si-Ge nanowires (NWs), based on solving the Boltzmann transport equation by the Monte Carlo method of sampling the phonon mean free paths. We augment the previous work with the full phonon dispersion and a partially diffuse momentum-dependent specularity model for boundary roughness scattering. We find that phonon flights are comprised of a mix of long free flights over several $\ensuremath{\mu}\mathrm{m}$ interrupted by bursts of short flights, resulting in a heavy-tailed distribution of flight lengths, typically encountered in L\'evy walk dynamics. Consequently, phonon transport in Si-Ge NWs is neither entirely ballistic nor diffusive; instead, it falls into an intermediate regime called superdiffusion where thermal conductivity scales with the length of the NW as $\ensuremath{\kappa}\ensuremath{\propto}{L}^{\ensuremath{\alpha}}$ with the exponent of length dependence $\ensuremath{\alpha}\ensuremath{\approx}0.33$ over a broad range of wire lengths $10\phantom{\rule{4pt}{0ex}}\mathrm{nm}lLl10\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$ regardless of diameter and roughness. We conclude that thermal conductivity in Si-Ge alloy NWs is length dependent up to $10 \ensuremath{\mu}\mathrm{m}$ and therefore can be tuned for thermoelectric applications.

This paper explores self-heating effects on junctionless gate-all-around nanowire MOSFET using self-consistently coupled 3D full band electro-thermal transport. The self-consistent algorithm begins by supplying the heat generation data from the 3D electron Monte Carlo with 2D quantum correction to the phonon Monte Carlo. Subsequently, the phonon Monte Carlo transports the phonons introduced from the electron simulation and considers their scattering through the anharmonic three-phonon processes. The anharmonic three-phonon decay and the use of full dispersion facilitate a detailed description of heat transfer and the determination of the temperature map. We compare the performance of gate-all-around junctionless against the conventional inversion mode gate-all-around MOSFET. Our results indicate that junctionless MOSFET has less self-heating effects than the conventional inversion mode device, particularly at the limits of high currents.