Abstract-Theoretical analysis of conditions for observation of plasma oscillations in semiconductors from pulsed terahertz emission

Antanas Reklaitis^1,a)

1 Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Goshtauto 11, Vilnius 01108, Lithuania
http://scitation.aip.org/content/aip/journal/jap/116/8/10.1063/1.4894163
a) Electronic address: reklaitis@pfi.lt.
J. Appl. Phys. 116, 083107 (2014); http://dx.doi.org/10.1063/1.4894163

Oscillations of electron-hole plasma generated by femtosecond optical pulse in freestandingsemiconductor are studied using hydrodynamic model and Monte Carlo simulations. The conditions required for the observation of coherent plasma oscillations in THz emission fromsemiconductor are determined. It is shown that several conditions have to be fulfilled in order to observe coherent plasma oscillations. First, the intensity of the optical pulse must exceed some threshold value. Second, the optical absorption depth must exceed the thickness of the built-in electric field region. Third, the generation of electron-hole pairs with uniform illumination is required, i.e., the laser beam with the flattop intensity profile has to be used. It is found that the duration of the optical pulse does not play a vital role in the development of plasma oscillations.

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