Electron-phonon coupling in semiconductors

Zlatan Aksamija, Beckman Institute, UIUC

Thermal budget is quickly emerging as the prominent limitation on future trends in scaling of semiconductor devices. Detailed understanding of electron-phonon coupling, as well as characteristics of the phonon heat generated by the electron current, such as phonon mode and spectrum, are crucial to our understanding of the micro-scale heating issues in semiconductor devices. We combine established numerical algorithms for Brillouin zone integration with the deformation potentials given in the literature to compute detailed electron-phonon scattering rates. The electronic band structure is obtained from non-local pseudo-potentials including strain, while the adiabatic bond-charge model is used for the phonon dispersion. The full-band Monte Carlo algorithm is applied, and the resulting electron distribution integrated to obtain the phonon emission spectrum for several electric field strengths. The phonon emission spectrum is then compared to the phonon density-of-states (DOS). We find that, with increasing field strength, longitudinal acoustic (TA) phonon emission and absorption decrease, while longitudinal acoustic (LA) emission increases to account for the overall increase in dissipation at high fields. This work gives us an opportunity to probe the nature of phonon emission and absorption in silicon in detail, and learn more about the trends in heat dissipation at high electric fields.