Free-carrier relaxation and lattice heating in photoexcited bismuth

Yu-Miin Sheu*, Y. J. Chien, C. Uher, S. Fahy, D. A. Reis

*Corresponding author for this work

Research output: Contribution to journalArticle

18 Scopus citations

Abstract

We report ultrafast surface pump and interface probe experiments on photoexcited carrier transport across single crystal bismuth films on sapphire. The film thickness is sufficient to separate carrier dynamics from lattice heating and strain, allowing us to investigate the time scales of momentum relaxation, heat transfer to the lattice, and electron-hole recombination. The measured electron-hole (e-h) recombination time is 12-26 ps and ambipolar diffusivity is 18-40 cm2/s for carrier excitation up to ∼1019cm - 3. By comparing the heating of the front and back sides of the film, we put lower limits on the rate of heat transfer to the lattice, and by observing the decay of the plasma at the back of the film, we estimate the time scale of electron-hole recombination. We interpret each of these time scales within a common framework of electron-phonon scattering and find qualitative agreement between the various relaxation times observed. We find that the carrier density is not determined by the e-h plasma temperature after a few picoseconds. The diffusion and recombination become nonlinear with initial excitation ≠3 1020cm - 3.

Original languageEnglish
Article number075429
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number7
DOIs
StatePublished - 19 Feb 2013

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