Caractérisation électro-optique de composants térahertz par échantillonnage Franz-Keldysh subpicoseconde

Abstract : The increasing flows of telecommunications need the realization of integrated circuits using transistors with increasing cut-off frequencies. The evaluation of the intrinsic performances of these devices that work today at several hundredth of GHz, presents one a difficult problem of instrumentation. The capacities of networks analyzers generally used for these measurements are indeed exceeded.

Electro-optic sampling methods based on a femtosecond pulsed laser constitute an alternative solution for microwave characterizations. These measurements can have a time resolution better than one picosecond and allow the study of integrated devices presenting a frequency response up to 1 THz.

The ultra-high speed sampling technique we propose is based on an electroabsorption effect in bulk semiconductors : the Franz-Keldysh effect. This effect allowed us to optically probe ultrafast electrical pulses propagating on a transmission line on Gallium Arsenide (GaAs). These pulses are generated also by an optical way using an ultrafast photoconductive material: GaAs grown by molecular beam epitaxy at low temperature.

The experimental demonstration of this characterization tool is first realized using the intrinsic properties of the semiconductor substrate. The obtained results show a very low invasiveness, a subpicosecond time resolution and a good sensitivity. In a second time, improvement is brought to the experimental set-up to extend the measurement technique to all kind of substrates. In this aim, we have used an epitaxial lift-off technique that consists in bonding with Vand der Waals forces a thin film of a semiconductor layer directly on the transmission line under test. We measured very clean electrical pulses with a 2.5 THz bandwidth.

These measurement techniques are applied to the characterization of several transmission lines or passive devices in the THz band. They allow for example the demonstration of shock wave coupling between coplanar striplines on GaAs or the evaluation of the S-parameters of an integrated Bragg filter up to 1.2 THz. The possibility to study the ultrafast behaviour of an Heterojunction Bipolar Transistor by electroabsorption sampling can now be contemplated.
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Contributor : Ludovic Desplanque <>
Submitted on : Friday, April 14, 2006 - 1:38:48 PM
Last modification on : Thursday, October 18, 2018 - 1:22:19 AM
Long-term archiving on : Saturday, April 3, 2010 - 11:11:43 PM

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  • HAL Id : tel-00012147, version 1

Citation

Ludovic Desplanque. Caractérisation électro-optique de composants térahertz par échantillonnage Franz-Keldysh subpicoseconde. Micro et nanotechnologies/Microélectronique. Université des Sciences et Technologie de Lille - Lille I, 2003. Français. ⟨tel-00012147⟩

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