Calculations reveal new insights into heat diffusion in silicon
Calculations reveal new insights into heat diffusion in silicon lead image
One of the main impediments to efficiency in electronic devices is the dissipation of heat produced by electrons traveling through the material, such as silicon, used to make device components. It has long been thought that hot electrons in silicon lose their energy mainly to optical phonons.
New calculations published in AIP’s Applied Physics Letters show that this is not the case. These calculations reveal that electrons in silicon lose over 50% of their energy to acoustic phonons, not optical ones.
Two co-authors of the current paper previously carried out Monte Carlo calculations independent of one another using two different physical models. One involved empirical pseudopotentials, and the other used Harris potentials. Both calculations showed that the widespread assumption of optical phonons involvement in energy dissipation in silicon was incorrect.
These early results, however, remained unpublished until now. In this latest study, the group performed calculations using density functional theory, or DFT, and found that, within the uncertainty that still affects DFT, the results are consistent with the early conclusions: The energy lost to acoustic phonons cannot be neglected.
Interestingly, the only direct experimental information available is inconsistent with the widely held assumption that optical phonons are involved in the heat-dissipation process. The results reported in this work clarify the discrepancy and show that early common assumptions that treated electron/acoustic-phonon scattering as elastic and the use of oversimplified physical models were incorrect.
The results from the study will be important for understanding electron transport, energy dissipation and heat generation in silicon-based electronic devices.
Source: “‘Hot electrons in Si lose energy mostly to optical phonons’: Truth or myth?,” by M. V. Fischetti, P. D. Yoder, M. M. Khatami, G. Gaddemane, and M. L. Van de Put, Applied Physics Letters (2019) The article can be accessed at https://doi.org/10.1063/1.5099914 .
