Generation of THz transients by photoexcited single-crystal GaAs meso-structures

Zhang, Jie; Mikulics, Martin; Sobolewski, Roman; Grützmacher, Detlev; Adam, Roman

doi:10.1007/s00340-013-5495-1

Journal Article

FZJ-2014-00596

Generation of THz transients by photoexcited single-crystal GaAs meso-structures

Zhang, J. (Corresponding author) ; Mikulics, M.FZJ* ; Adam, R.FZJ* ; Grützmacher, D.FZJ* ; Sobolewski, R.

2013
Springer Berlin

Applied physics / B 113(3), 339 - 344 (2013) [10.1007/s00340-013-5495-1]

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Please use a persistent id in citations: http://hdl.handle.net/2128/5815 doi:10.1007/s00340-013-5495-1

Abstract: We report a sub-picosecond photoresponse and THz transient generation of GaAs single-crystal mesoscopic platelets excited by femtosecond optical pulses. Our structures were fabricated by a top-down technique, by patterning an epitaxial, 500-nm-thick GaAs film grown on top of an AlAs sacrificial layer and then transferring the resulting etched away 10 9 20-lm2 platelets onto an MgO substrate using a micropipette. The freestanding GaAs devices, incorporated into an Au coplanar strip line, exhibited extremely low dark currents and *0.4 % detection efficiency at 10 V bias. The all-optical, pump–probe carrier dynamics analysis showed that, for 800-nmwavelengthexcitation, the intrinsic relaxation of photocarriersfeatured a 310-fs-wide transient with a 290 fs falltime. We have also carried out a femtosecond, timeresolved electro-optic characterization of our devices and recorded along the transmission line the electrical transients as short as *600 fs, when the platelet was excited by a train of 100-fs-wide, 800-nm-wavelength optical laser pulses. The platelets have been also demonstrated to be very efficient generators of free-space propagating THz transients with the spectral bandwidth exceeding 2 THz. The presented performance of the epitaxial, freestanding GaAs meso-structured photodevices makes them uniquely suitable for THz-frequency optoelectronic applications, ranging from ultrafast photodetectors to THz-bandwidth optical-to-electrical transducers and photomixers.

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