Theory of Thermal Relaxation of Electrons in Semiconductors

Journal Article · Fri Sep 01 00:00:00 EDT 2017 · Physical Review Letters

DOI:https://doi.org/10.1103/PhysRevLett.119.136602· OSTI ID:1427544

Sadasivam, Sridhar; Chan, Maria K. Y.; Darancet, Pierre

We compute the transient dynamics of phonons in contact with high energy ``hot'' charge carriers in 12 polar and non-polar semiconductors, using a first-principles Boltzmann transport framework. For most materials, we find that the decay in electronic temperature departs significantly from a single-exponential model at times ranging from 1 ps to 15 ps after electronic excitation, a phenomenon concomitant with the appearance of non-thermal vibrational modes. We demonstrate that these effects result from the slow thermalization within the phonon subsystem, caused by the large heterogeneity in the timescales of electron-phonon and phonon-phonon interactions in these materials. We propose a generalized 2-temperature model accounting for the phonon thermalization as a limiting step of electron-phonon thermalization, which captures the full thermal relaxation of hot electrons and holes in semiconductors. A direct consequence of our findings is that, for semiconductors, information about the spectral distribution of electron-phonon and phonon-phonon coupling can be extracted from the multi-exponential behavior of the electronic temperature.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1427544
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 13 Vol. 119; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English