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Title: Magnetotransport studies of InAs/GaSb/AlSb-based structures
Author: Cooper, L. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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A reliable procedure has been developed which facilitates the fabrication of low-leakage front and back gated lateral transport devices in which electrons and holes reside in adjacent layers. This gating permits the alteration of the electron and hole densities in such devices almost independently of one another. A simple processing technique has also been developed for resonant inter-band and hybrid inter/intra-bond tunnelling devices. In the absence of a barrier between the layers in which the charge resides, it is shown that the wavefunctions of electrons and holes hybridise, causing an energy gap to form in the dispersion relation of the hybrid particles. This manifests itself in lateral transport measurements as a resistance peak when the Fermi energy in the system is made to lie in this "gap" by the action of the gates. The resistance resonance is seen to disappear as a function of temperature and in-plane magnetic field. The results of a simple numerical model are shown to predict the broad features in the experimental data and allow the extraction of the magnitude of the energy gap in the system. Anomalous low-field positive magnetoresistance in an in-plane magnetic field is discussed in the context of wavefunction movement in the growth plane and the antilocalisation effects of asymmetry. In a perpendicular magnetic field, Landau levels are formed in the system and the transport shows Shubnikov-de Haas oscillations and quantum Hall plateaux originating from either carrier type. So-called "compensated Hall plateaux" are observed and the absence of a completely compensated "v=0" plateau is discussed. Magnetic field induced charge transfer between the electron and hole layers which depends on the inter-layer tunnelling is observed. Tilted magnetic field measurements are performed to extract the effective g-factor of the electrons in the system and the effect of electron-hole coupling on its value is discussed.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available