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Title: Spin dependent electron transport in nanoscale InSb quantum well devices
Author: Li, Juerong
ISNI:       0000 0004 2709 3286
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2011
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Spin dependent magneto-transport provides a way of injecting, manipulating and detecting spins in spintronic technologies. In the laboratory large magnetic fields are commonly used to produce spin populations in semiconductors via the Zeeman Effect. However, the use of large fields in consumer electronics is not a viable option. InSb quantum wells (QWs) are appealing candidates for the study of spin-dependent phenomena due to their large spin-orbit interactions that lead to a large splitting in spins. In this thesis, the spin-dependent transport is investigated in narrow gap InSb/InAlSb QW devices using small magnetic fields (less than 200 mT). Investigating the spin dependent effects requires introducing a spin polarised current and measuring the spin dependent resistance of the nanoscale devices. This can be achieved by photo-exciting spins using circularly polarised light. In addition, photoinduced current enables us to eliminate the parallel conduction which obscures the contribution of the quantum well. Spin-dependent transport is more pronounced in ballistic regime as it reduces the probability of spin randomization by impurity scattering. Therefore, the determination of ballistic transport was performed by means of observing the negative bend resistance as well as the quenching of Hall effect. Due to the spin dependent cyclotron radius caused by spin-orbit coupling, spin dependent photocurrents have been obtained in longitudinal resistance and transverse electron focusing nanoscale geometries. Hence, by tuning a small magnetic field, spin filtering properties that do not require the inclusion of magnetic materials could be achieved. This provides a way of producing spin injectors, spin manipulators and spin detectors. Simulations of the spin dependent signal are also presented using a classical billiard-ball model which includes both spin precession and a spin energy term. The simulation suggests the spin dependent signal is not expected to be observed in linear polarised photocurrents and purely electrical measurements.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available