Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

Y. D. Jho; D. S. Kim; A. J. Fischer; J. J. Song; J. Kenrow; K. El Sayed; C. J. Stanton

doi:10.1103/PhysRevB.68.165325

Exceptionally slow rise in differential reflectivity spectra of excitons in GaN: Effect of excitation-induced dephasing

Y. D. Jho, D. S. Kim, A. J. Fischer, J. J. Song, J. Kenrow, K. El Sayed, and C. J. Stanton

Phys. Rev. B 68, 165325 – Published 20 October 2003

Abstract

Femtosecond differential reflectivity spectroscopy (DRS) and four-wave mixing (FWM) experiments were performed simultaneously to study the initial temporal dynamics of the exciton line-shapes in GaN epilayers. Beats between the $A - B$ excitons were found only for positive time delay in both DRS and FWM experiments. The rise time at negative time delay for the DRS was much slower than the FWM signal or differential transmission spectroscopy at the exciton resonance. A numerical solution of a six band semiconductor Bloch equation model including nonlinearities at the Hartree-Fock level shows that this slow rise in the DRS results from excitation induced dephasing, that is, the strong density dependence of the dephasing time which changes with the laser excitation energy.

Received 28 January 2003

DOI:https://doi.org/10.1103/PhysRevB.68.165325

Authors & Affiliations

Y. D. Jho^*

National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA

D. S. Kim

Department of Physics, Seoul National University, Seoul 151-747, Korea

A. J. Fischer and J. J. Song

Department of Physics and Center for Laser Research, Oklahoma State University, Stillwater, Oklahoma 74078, USA

J. Kenrow^†, K. El Sayed, and C. J. Stanton

Department of Physics, University of Florida, Gainesville, Florida 32611, USA

^*Electronic address: ydjho@mail.magnet.fsu.edu
^†Present address: Dept. of Electrical and Computer Engineering, University of the Pacific, Stockton, CA 95211.

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Vol. 68, Iss. 16 — 15 October 2003

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