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Technology development for nanoscale InSb quantum split-gate structures

Jubair, Shawkat 2019. Technology development for nanoscale InSb quantum split-gate structures. PhD Thesis, Cardiff University.
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In this project some of the challenges of novel InSb based semiconducting material are investigated. Various features of electron transport in low dimensional semiconductors were studied for AlInSb/InSb quantum well (QW) two-dimensional electron gas (2DEG) heterostructures with an emphasis placed on realising onedimensional systems (which exhibit quantum phenomena where the conductance takes on a discrete ‘step-like’ nature). This material allows us to take advantage of very extreme material parameters such as light effective mass, the lowest binary material band gap, the highest electron mobility at room temperature, and an extremely large effective g-factor (with associated spin orbit coupling). However, this material still has significant challenges due to the large mismatch between the substrate GaAs and the QW, which produces threading dislocations that lead to limitations in mobility. Surface roughness has been investigated as a result of shallow etching for Ohmic contact deposition on the AlInSb/InSb wafer. Both dry and wet techniques have been investigated, and their effect on the electron transport as a function of roughness, primarily using Transmission Length Measurement (TLM). In addition, the Ohmic contact resistivity was investigated as a function of depth over a wide range of temperatures to extract an effective contact barrier. The contact potential barrier was found to have a strong effect at low temperatures, which leads to a non-linear I-V characteristic. Finally, this thesis studied different designs of nanoscale split gate structures that were fabricated on this state of the art InSb QW 2DEG material. This material was grown by collaborators at Sheffield University at the National Centre for III-V technologies. The devices were fabricated at Cardiff using photo-lithography and nanoscale electron beam lithography (EBL) using recipes tailored to this material.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Uncontrolled Keywords: InSb Semiconductors, low dimensional semiconductors, AlInSb/InSb quantum well two-dimensional electron gas heterostructures, nanoscale split gate structures
Funders: Iraqi Government Sponsorship
Date of First Compliant Deposit: 19 December 2019
Last Modified: 20 Oct 2021 01:17

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