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Optical time resolved spin dynamics in III-V semiconductor quantum wells

Optical time resolved spin dynamics in III-V semiconductor quantum wells
Optical time resolved spin dynamics in III-V semiconductor quantum wells

This thesis presents time-resolved measurements of the spin evolution of transient carrier populations in III-V quantum wells.  Non-equilibrium distributions of spin polarisation were photoexcited and probed with picosecond laser pulses in three samples; a high mobility modulation n-doped sample containing a single GaAs/AlGaAs quantum well, an In0.11Ga0.89As/GaAs sample containing three quantum wells and, a multi-period GaAs/AlGaAs narrow quantum well sample.

Electron spin polarisation in low mobility wells decays exponentially.  This is successfully described by the D’yakonov-Perel (DP) mechanism under the frequent collision regime, within which the mobility can be used to provide the scattering parameter.  This work considers the case of high mobility sample where collisions are infrequent enough to allow oscillatory spin evolution.  It is shown however, that in n-type quantum wells the electron-electron scattering inhibits the spin evolution, leading to slower, non-oscillatory, decays than previously expected. 

Observed electron spin relaxation in InGaAs/InP is faster that in GaAs/AlGaAs.  This may be ascribed to an enhanced DP relaxation caused by Native Interface Asymmetry (NIA) in InGaAs/InP, or to the differing natures of the well materials.  Here the two possibilities have been distinguished by measuring electron spin relaxation in InGaAs/GaAs quantum wells.  The long spin lifetime implicates the NIA as the cause of the fast relaxation in InGaAs/InP.

Finally, the reflectively probed optically induced linear birefringence method has been used to measure quantum beats between the heavy-hole exciton spin states, which are mixed by a magnetic field applied at various angles to the growth direction of the GaAs/AlGaAs multi-quantum well sample within which the symmetry is lower than D2d.  Mixing between the optically active and inactive exciton spin states by the magnetic field, and between the two optically active states by the low symmetry, are directly observed.

University of Southampton
Brand, Matthew Anthony
Brand, Matthew Anthony

Brand, Matthew Anthony (2003) Optical time resolved spin dynamics in III-V semiconductor quantum wells. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This thesis presents time-resolved measurements of the spin evolution of transient carrier populations in III-V quantum wells.  Non-equilibrium distributions of spin polarisation were photoexcited and probed with picosecond laser pulses in three samples; a high mobility modulation n-doped sample containing a single GaAs/AlGaAs quantum well, an In0.11Ga0.89As/GaAs sample containing three quantum wells and, a multi-period GaAs/AlGaAs narrow quantum well sample.

Electron spin polarisation in low mobility wells decays exponentially.  This is successfully described by the D’yakonov-Perel (DP) mechanism under the frequent collision regime, within which the mobility can be used to provide the scattering parameter.  This work considers the case of high mobility sample where collisions are infrequent enough to allow oscillatory spin evolution.  It is shown however, that in n-type quantum wells the electron-electron scattering inhibits the spin evolution, leading to slower, non-oscillatory, decays than previously expected. 

Observed electron spin relaxation in InGaAs/InP is faster that in GaAs/AlGaAs.  This may be ascribed to an enhanced DP relaxation caused by Native Interface Asymmetry (NIA) in InGaAs/InP, or to the differing natures of the well materials.  Here the two possibilities have been distinguished by measuring electron spin relaxation in InGaAs/GaAs quantum wells.  The long spin lifetime implicates the NIA as the cause of the fast relaxation in InGaAs/InP.

Finally, the reflectively probed optically induced linear birefringence method has been used to measure quantum beats between the heavy-hole exciton spin states, which are mixed by a magnetic field applied at various angles to the growth direction of the GaAs/AlGaAs multi-quantum well sample within which the symmetry is lower than D2d.  Mixing between the optically active and inactive exciton spin states by the magnetic field, and between the two optically active states by the low symmetry, are directly observed.

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Published date: 2003

Identifiers

Local EPrints ID: 465118
URI: http://eprints.soton.ac.uk/id/eprint/465118
PURE UUID: 6c4ac6ae-3f7b-4b45-aad7-8a7cf2b6f326

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Date deposited: 05 Jul 2022 00:24
Last modified: 05 Jul 2022 04:16

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Author: Matthew Anthony Brand

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