Electronic transport and structure of a surface quantum well

Kan, Carolyn

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https://hdl.handle.net/2142/101463 Copy

Description

Title

Electronic transport and structure of a surface quantum well

Author(s)

Kan, Carolyn

Issue Date

2018-05-15

Director of Research (if dissertation) or Advisor (if thesis)

Eckstein, James N.

Doctoral Committee Chair(s)

Mason, Nadya

Committee Member(s)

• Vishveshwara, Smitha
• Zuo, Jian-Min

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• proximity effect
• surface quantum well

Abstract

Lattice-mismatched heteroepitaxy is present in the growth of any thin-film heterostructure, and has inevitable consequences on the nature of film growth. A mismatch in the lattice parameter between two materials leads to strain within both films, which can lead to dislocations and deformations in the lattices. The formation of dislocations is a complex phenomenon with both thermodynamic and kinetic influences. In this work, a structural study of antimonide buffer layers on GaAs substrates was performed. Using in situ diffraction and ex situ microscopy, we examine the lattice transition between GaAs substrates, and the highly mismatched material GaSb. When GaSb grows on GaAs, it follows a complex Stranski-Krastanov 2D to 3D transition. Using our real-time diffraction data, we determine that the change in lattice constant and the transition to 3D growth occur simultaneously. Our work on the growth of antimonides is motivated by the desire to grow high quality InAs films. InAs is closely lattice-matched to the antimonide compounds studied, making them candidates for the composition of buffer layers on which to grow InAs. The superconducting proximity effect in a highly spin-orbit coupled material such as InAs is key to the realization of Majorana zero modes and future advances in topological computing. The surface accumulation layer that InAs forms when in contact with a superconductor makes it ideal for proximity effect-based devices, as the carriers are physically connected to the superconductor. We grew and measured InAs surface quantum wells grown on GaSb buffers, characterizing their electronic properties and preparing measurements of the proximity effect in the wells. While electrons in the InAs surface quantum wells are scattered more than those buried InAs quantum wells, an electron mean free path approaching 100~nm was obtained. Fabrication methods are being developed for the creation of Josephson junction arrays on our InAs films, with which the proximity effect can be studied.

Graduation Semester

2018-08

Type of Resource

text

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http://hdl.handle.net/2142/101463

Copyright and License Information

Copyright 2018 Carolyn Kan

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