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Theses

Transport polarisé en spin dans des nanostructures semiconductrices

Abstract : In the field of spin-electronic, the integration of magnetic materials in semiconductor heterostructures is promising for a new generation of electronic devices where two degrees of freedom will be associated: spin and charge of carriers. The outcome of this thesis is an electrical detection of spin injection into a GaAs quantum well. In order to do so, we have first studied thin films of the ferromagnetic semiconductor GaAs doped Mn and GaMnAs-based magnetic tunnel junctions. Magnetic and transport studies on GaMnAs thin films have shown that the magnetic and electronic properties are intimately connected. The spin polarization of carriers (40%) has been established from the magnetoresistance (MR) of the magnetic tunnel junction. Then we have elaborated heterostructures where two GaMnAs electrodes are separated by an AlAs/GaAs/AlAs quantum well. The first GaMnAs ferromagnetic electrode is used to polarize the carriers and the second to analyze the spin-polarized current injected in the quantum well. The MR, in these structures, is attributed to a sequential tunneling with a spin accumulation in the GaAs well. The high MR obtained (40%) is the signature of the spin conservation in the well. The spin lifetime is therefore longer than the tunneling time (time spent by the hole in the well). We have studied the influence of these two times on the MR. These studies have allowed us to establish required conditions to achieve an electrical detection of spins injected in a semiconductor quantum well. These all-electrical experiments have also allowed us to determine the spin lifetime of holes in a GaAs quantum well. Hole spin lifetime in these GaAs quantum well is longer than hundred picoseconds at 4.2K.
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Theses
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https://tel.archives-ouvertes.fr/tel-00004917
Contributor : Richard Mattana <>
Submitted on : Monday, February 23, 2004 - 9:39:05 AM
Last modification on : Wednesday, June 3, 2020 - 10:30:04 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:37:25 PM

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  • HAL Id : tel-00004917, version 1

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Richard Mattana. Transport polarisé en spin dans des nanostructures semiconductrices. Matière Condensée [cond-mat]. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00004917⟩

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