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Etude théorique et expérimentale de la génération térahertz par photocommutation dans des composants en GaAs basse température

Abstract : The aim of this work was to characterize and modelize a semiconductor photoswitch device that can generate subpicosecond electrical pulses. This device is an interdigital comb located in the central line of a gold coplanar waveguide layed deposited over a low-temperature-grown GaAs layer doped with beryllium. By exciting this polarized detector with a femtosecond laser pulse, picosecond and sub-picosecond electrical pulses are generated. The pulse duration is approximately equal to the electron lifetime in the semiconductor. A comparative study of several characterization methods (photoconductive, electro-optic and electroabsorption samplings) was done. The advantages and drawbacks of each technique are given. Measurements show the influence of the material and microwave circuit dynamics on the device response. Especially, an increase of the electron lifetime caused by trap level saturation is observed, as well as the influence of the detector capacity on the device response and the limitation of the amplitude of pulses caused by the line impedance. To describe the experimental data, we built a simple model based on an electrical equivalent circuit, that takes into account material and microwave responses of the device. The agreement between theory and experiment is good. This allows us to understand the dynamics of the physical and electrical parameters when the detector is excited by two consecutive optical pulses. This photoconductive pump-probe measurement shows clearly the relaxation time of the photoswitch and the trap saturation. Finally, the model allows us to calculate the bandwith of the device when used in a photomixing experiment.
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https://tel.archives-ouvertes.fr/tel-00009562
Contributor : Hervé Eusèbe <>
Submitted on : Wednesday, June 22, 2005 - 11:33:06 AM
Last modification on : Friday, November 6, 2020 - 3:27:57 AM
Long-term archiving on: : Friday, April 2, 2010 - 10:38:26 PM

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  • HAL Id : tel-00009562, version 1

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Hervé Eusèbe. Etude théorique et expérimentale de la génération térahertz par photocommutation dans des composants en GaAs basse température. Matière Condensée [cond-mat]. Institut National Polytechnique de Grenoble - INPG, 2004. Français. ⟨tel-00009562⟩

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