Special CPM Seminar

Fabrication and characterization of gate-defined structures in metamorphic InAs heterostructures

Javad Shabani

California NanoSystems Institute
University of California Santa Barbara

Theory and recent experiments suggest that nanowires of narrow band gap semiconductors, such as InAs, are a suitable platform for realization of topological states of matter. Molecular beam epitaxy (MBE) growth of large area InAs two-dimensional systems (2DESs) combined with semiconductor processing techniques (top-down approach) provides an avenue toward substantially more complex architectures than can be achieved using vapor-liquid-solid self-assembled nanowires. Fabrication of gate-defined devices on these heterostructures is highly desirable as it offers the possibility of tuning confinement potential, carrier density and spin orbit coupling while maintaining the mobility of the parent 2DES. However, reliable gating has proven difficult in InAs due to gate leakage and hysteretic behavior. In this talk, we show that these difficulties could be surmounted using epitaxial growth of strained InAs quantum wells in metamorphic heterostructures. At liquid helium temperature electron mobilities in excess of 400,000 cm²/Vs are now achieved. The gate-controlled mobility dependence on carrier density indicates mobility is limited due to scattering from background impurities. Consistent with this picture, we find a metal insulator transition at very low critical density. We also demonstrate the first gate-defined one-dimensional channels on high mobility InAs 2DES and discuss their future prospects for fabricating hybrid superconducting-InAs devices.