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Toward a zinc oxide based quantum cascade laser

Abstract : The Terahertz domain (THz), situated between the visible and microwave energy range, turns out to be very promissing in terms of applications. However its application potential is not fully used because of the lack for compact sources able to cover a large part of its energy range. Quantum Cascade Lasers (QCL) are good candidates for this purpose, because there are both compact and highly tunable. But in the THz range, the existing QCLs suffer from the operation temperature limitation ( 200K ), which is very restricting from the application viewpoint. It comes from an intrinsic property of the materials commonly used to build QCLs: the LO-phonon energy. As a consequence a strong competition between the LO-phonon transition and the QCL radiative transition arise at room temperature, which hinder the lasing efficiency. To tackle this issue, we choose to make use of ZnO, because its LO-phonon energy is twice larger compared to the aforementioned materials, thus enabling to keep the lasing action efficient at room temperature. Even if ZnO and its related alloys are not new in the field of semiconductor science, they are totally exotic for the QCL field. Indeed, QCL are built from highly periodic heterostructures, from which all the key device properties come from. Therefore, the heterostructure should be controlled at the monolayer scale and this precision should be reproducible on hundred of periods, which made QCL growth an indubitabble challenge. This thesis aims at take up this challenge by bringing ZnO/(Zn, Mg)O heterostructures to this ultime degree of control. We are growing ZnO/(Zn, Mg)O heterostructures on ZnO substrates with a new molecular beam epitaxy system and we demonstrate that the heterostructures quality matche the QCL material requirements. This first step enables us to demonstrate the observation of intersubband transitions in the mid-infrared range until room temperature, as well as their coupling within asymmetric quantum well structures. Complete cascade structures were also grown and lead to the first demonstration of a ZnO based Quantum Cascade Detector in the infrared range until room temperature. QCL structures were also grown and shows very good heterostructure control as stated by scanning transmission electron microscopy experiments.
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Submitted on : Tuesday, June 2, 2020 - 5:48:11 PM
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  • HAL Id : tel-02736475, version 1

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Nolwenn Le Biavan. Toward a zinc oxide based quantum cascade laser. Physics [physics]. COMUE Université Côte d'Azur (2015 - 2019), 2019. English. ⟨NNT : 2019AZUR4070⟩. ⟨tel-02736475⟩

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