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Title: The characterisation of InSb quantum well heterostructures by electrical measurement
Author: Smith, George St J. V.
ISNI:       0000 0004 7652 6180
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2019
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This thesis describes both experimental and theoretical work on the electronic transport properties of 30 nm InSb/AlInSb quantum well 2DEG heterostructures. Advances in the epitaxial growth of large lattice constant III-V materials using mismatched substrates like GaAs or Si has generated renewed interest in developing high mobility devices. Similarly, narrow gap semiconductors are promising candidates for the advancement of spintronic devices taking advantage of their extreme material parameters, such as the small effective mass and large effective Landé g-factor. An investigation of the low temperature Hall effect and Shubnikov-de Haas oscillations of asymmetrically doped InSb quantum well heterostructures has been made to determine the scattering mechanisms present for carriers in the 2D system. Modelling these oscillations by calculation of the density of states at the Fermi energy as a function of magnetic field was performed to analyse the effects of parameter variation on the observed oscillation. Application of a dielectric layer and gate electrode to the material surface has allowed for a carrier density dependent investigation of the transport properties to be performed. These investigations have provided a detailed understanding of the transport limiting scattering mechanisms over a range of carrier densities and temperatures. A novel study of the current-voltage characteristics of high resistance contacts has been performed to investigate the energetic distribution of electron states in the quantum well under the application of large magnetic fields. Clear Landau level quantisation of the 2D density of states for the first subband of the quantum well has been observed. Analysis of the high field asymmetry of the fundamental Landau level has revealed the presence of significant spin dependent broadening within the heterostructure, which has previously been suggested to exist from an asymmetry of the Fourier transform of Shubnikov-de Haas oscillation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics