Coherence and Lifetime of Excitons in Core-Shell GaAs/AlGaAs Nanowires
ORAL
Abstract
Three-beam heterodyne four-wave mixing (HFWM) measurements of the ultrafast coherent and lifetime dynamics of excitons in Au catalyzed MOVPE grown GaAs/AlGaAs/GaAs core-shell-cap nanowires will be presented. Measurements exploring the excitation wavelength dependance of the coherent decay dynamics will be shown, highlighting the shift from mainly homogenous broadening with excitation pulse energy at the band gap to slight inhomogeneous broadening below the gap energy. Power dependent HFWM experiments display a decrease in the coherence time for excitons when excited at high powers. A fast dephasing time (of <1 ps) obtained is attributed to a high electron-hole pair scattering rate. HFWM measurements in “lifetime configuration” reveal a biexponential decay of 3 and 175 ps. The fast and slow lifetimes are related to fast capturing of excitons at surface states or defects at the AlGaAs interface, and radiative recombination, respectively. A 5-level third order model and an all order 2-level model displaying the occurrence of a photon echo and coherence observed in the nanowires will also be presented.
*Support from the National Science Foundation (NSF, grant DMR-2004768), the Australian Research Council (ARC) and the Australian National Fabrication Facility, ACT Node, and the Graduate Student Government (GSG) at the University of Cincinnati are gratefully acknowledged.
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Presenters
Matthew T Larson
University of Cincinnati
Authors
Matthew T Larson
University of Cincinnati
Samia Alyami
Department of Physics, University of Cincinnati, Cincinnati, University of Cincinnati
Carsten A Ullrich
University of Missouri
Naiyin Wang
Australian National University, The Australian National University
Hark Hoe Tan
The Australian National University, Australian National University
Chennupati Jagadish
Australian Natl Univ
Hans Peter Wagner
University of Cincinnati, University Of Cincinnati
