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.

The ultralow thermal conductivity $\kappa$ observed experimentally in intentionally roughened silicon nanowires (SiNWs) is reproduced in phonon Monte Carlo simulations with exponentially correlated real-space rough surfaces similar to measurement [J. Lim, K. Hippalgaonkar, S. C. Andrews, A. Majumdar, and P. Yang, Nano Lett. 12, 2475 (2012)]. Universal features of thermal transport are revealed by presenting $\kappa$ as a function of the normalized geometric mean free path $\bar\lambda$ ($0<\bar\lambda<1$); the diffusive (Casimir) limit corresponds to $\bar\lambda=1/2$. $\kappa$ vs $\bar\lambda$ is exponential at low-to-moderate roughness (high $\bar\lambda$), where internal scattering randomly interrupts phonon bouncing across the SiNW, and linear at high roughness (low $\bar\lambda$), where multiple scattering events at the same surface results in ultralow, amorphous-limit thermal conductivity.