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ÉMISSION et MODULATION INTERSOUSBANDE dans les NANOSTRUCTURES de NITRURES

Abstract : Intersubband transitions in semiconductor heterostructures have been intensively studied since the mid 80s. Nowadays there are two frontiers to explore: extending the operation of intersubband devices to the THz domain and to the near infra-red range. To reach the optical fiber telecommunication spectral range, the GaN/AlN quantum wells and quantum dots under investigation in this manuscript are the most promising candidates due to their large conduction band offset (1.75 eV).
I first present room-temperature experiments on GaN/AlN quantum wells grown by molecular beam epitaxy on sapphire substrate (0001). I report on the resonant enhancement of second harmonic generation at λ~1 µm as well as the first observation of intersubband emission at λ~2.1 µm under an optical pumping at room temperature.
I then study the electron quantum confinement in GaN/AlN coupled quantum wells and demonstrate the electron tunnelling between the two quantum wells under applied bias. This process is then applied to the realization of a fast electro-optical modulator (3 GHz).
Finally, I investigate the quantum confinement in GaN/AlN quantum dots. In these nano-objects, I describe the observation of intraband emission between the pz and s states at λ~1.48 µm at room temperature. These measurements allow to estimate the homogeneous broadening of the intraband transition in a single quantum dot. I then present pump-probe experiments aimed at measuring the lifetime of excited electrons, T1~160 fs. The dephasing time of electrons between the quantum dot states is estimated to be T2~320 fs based on absorption saturation and emission measurements.
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https://tel.archives-ouvertes.fr/tel-00282996
Contributor : Laurent Nevou <>
Submitted on : Wednesday, May 28, 2008 - 6:25:14 PM
Last modification on : Wednesday, September 16, 2020 - 4:54:14 PM
Long-term archiving on: : Friday, May 28, 2010 - 6:36:23 PM

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  • HAL Id : tel-00282996, version 1

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Laurent Nevou. ÉMISSION et MODULATION INTERSOUSBANDE dans les NANOSTRUCTURES de NITRURES. Physique [physics]. Université Paris Sud - Paris XI, 2008. Français. ⟨tel-00282996⟩

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