Abstract-Laser generation of hypersound by a terahertz photo-Dember electric field in a piezoelectric GaAs semiconductor

Gwenaelle Vaudel, Thomas Pezeril, Alexei Lomonosov, Marius Lejman, Pascal Ruello, and Vitalyi Gusev
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.014302

We experimentally demonstrate the optical generation of hypersound in a piezoelectric GaAs semiconductor through laser excitation of the THz photo-Dember electric field. Such an ultrashort transient Dember electric field is linked to the spatial separation of photoexcited electrons and holes right after above-band-gap femtosecond laser excitation. Through time-domain coherent Brillouin scattering we demonstrate that photoinduced piezoelectric generation of hypersound can dominate even in the absence of preexisting built-in fields and we observe, with increasing laser fluence, a nonlinear optoacoustic excitation process. These results reveal the onset of the THz photo-Dember electric field and highlight the transition from non-ambipolar flow to ambipolar diffusion of the photoexcited electron-hole plasma.

DOI: http://dx.doi.org/10.1103/PhysRevB.90.014302

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• Published 9 July 2014
• Received 23 December 2013
• Revised 20 June 201