TY - BOOK

T1 - Enhancing Transparent Superconductor-Semiconductor Hybrids

T2 - Advances enabling future experiments in proximitized InAs(Sb) systems

AU - Drachmann, Asbjørn Cennet Cliff

PY - 2020

Y1 - 2020

N2 - Superconductor-semiconductor hybrids are studied, mainly due to the potential discovery of Majorana zero modes that could facilitate scalable quantum computers. Improving material quality and fabrication processes is believed necessary in order to realize Majorana zero mode applications. Important aspects of device processing include patterning and removal of superconducting material, which can lead to disorder/irregularities of the hybrid. This thesis investigates new techniques for superconductor patterning. We demonstrate the prospects of using anodic oxidation on transparent superconductor-semiconductor hybrids, specifically on shallow InAs 2-dimensional electron gas (2DEG) heterostructures terminated with epitaxially grown Al. Partial oxidation of Al increases its superconducting critical temperature and critical magnetic fields. Compared to using a regular Al etch, a full Al oxidation passivates the underlying 2DEG, enhancing the carrier properties. Quantum Hall effect is achieved one tesla below the highest achieved critical field of oxidized Al. Using a metal mask for lithography enables a lateral resolution <50 nm with anodic oxidation. The mask is used to construct a magnetic field resilient Josephson junction. The novel system of a disordered superconductor with transparent coupling to an underlying 2DEG, shows1/B periodic magnetoresistivity oscillations both belowand above the superconducting critical field. In particular, the oscillations below the critical field is studied as a function of magnetic field, temperature and DC current. Lastly, suggestions for improvements of the anodic oxidation setup and for further material upgrades are elaborated.

AB - Superconductor-semiconductor hybrids are studied, mainly due to the potential discovery of Majorana zero modes that could facilitate scalable quantum computers. Improving material quality and fabrication processes is believed necessary in order to realize Majorana zero mode applications. Important aspects of device processing include patterning and removal of superconducting material, which can lead to disorder/irregularities of the hybrid. This thesis investigates new techniques for superconductor patterning. We demonstrate the prospects of using anodic oxidation on transparent superconductor-semiconductor hybrids, specifically on shallow InAs 2-dimensional electron gas (2DEG) heterostructures terminated with epitaxially grown Al. Partial oxidation of Al increases its superconducting critical temperature and critical magnetic fields. Compared to using a regular Al etch, a full Al oxidation passivates the underlying 2DEG, enhancing the carrier properties. Quantum Hall effect is achieved one tesla below the highest achieved critical field of oxidized Al. Using a metal mask for lithography enables a lateral resolution <50 nm with anodic oxidation. The mask is used to construct a magnetic field resilient Josephson junction. The novel system of a disordered superconductor with transparent coupling to an underlying 2DEG, shows1/B periodic magnetoresistivity oscillations both belowand above the superconducting critical field. In particular, the oscillations below the critical field is studied as a function of magnetic field, temperature and DC current. Lastly, suggestions for improvements of the anodic oxidation setup and for further material upgrades are elaborated.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/1pioq0f/alma99123828752805763

M3 - Ph.D. thesis

BT - Enhancing Transparent Superconductor-Semiconductor Hybrids

PB - Niels Bohr Institute, Faculty of Science, University of Copenhagen

ER -