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Broadband optical ultrafast reflectivity of Si, Ge and GaAs

Authors
  • Di Cicco, A.1, 2
  • Polzoni, G.1
  • Gunnella, R.1
  • Trapananti, A.1, 2
  • Minicucci, M.1
  • Rezvani, S. J.1
  • Catone, D.3
  • Di Mario, L.3
  • Pelli Cresi, J. S.3
  • Turchini, S.3
  • Martelli, F.4
  • 1 University of Camerino, Camerino, 62032, Italy , Camerino (Italy)
  • 2 INFN, Sezione di Perugia, Perugia, 06123, Italy , Perugia (Italy)
  • 3 Istituto di Struttura della Materia (ISM), CNR, Rome, 00133, Italy , Rome (Italy)
  • 4 Istituto per la Microelettronica e i Microsistemi (IMM), CNR, Rome, 00133, Italy , Rome (Italy)
Type
Published Article
Journal
Scientific Reports
Publisher
Springer Nature
Publication Date
Oct 15, 2020
Volume
10
Issue
1
Identifiers
DOI: 10.1038/s41598-020-74068-y
Source
Springer Nature
License
Green

Abstract

Ultrafast optical reflectivity measurements of silicon, germanium, and gallium arsenide have been carried out using an advanced set-up providing intense subpicosecond pulses (35 fs FWHM, λ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda $$\end{document} = 400 nm) as a pump and broadband 340–780 nm ultrafast pulses as a white supercontinuum probe. Measurements have been performed for selected pump fluence conditions below the damage thresholds, that were carefully characterized. The obtained fluence damage thresholds are 30, 20.8, 9.6 mJ/cm2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {cm}^2$$\end{document} for Si, Ge and GaAs respectively. Ultrafast reflectivity patterns show clear differences in the Si, Ge, and GaAs trends both for the wavelength and time dependences. Important changes were observed near the wavelength regions corresponding to the E1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_1$$\end{document}, E1+Δ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_1+\Delta $$\end{document} singularities in the joint density of states, so related to the peculiar band structure of the three systems. For Ge, ultrafast reflectivity spectra were also collected at low temperature (down to 80 K) showing a shift of the characteristic doublet peak around 2.23 eV and a reduction of the recovery times.

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