QDev Seminar: Javad Shabani

Fabrication and characterization of gate-defined structures in epitaxially grown InAs heterostructures

Fabrication of gate-defined devices on epitaxially grown heterostructures containing InAs layers is highly desirable as it offers the possibility of tuning the confinement potential, carrier density and spin orbit coupling. However, reliable gating has proven difficult in these materials due to gate leakage and hysteretic behavior. In addition, charge traps and Fermi level pinning could screen the applied electric field and significantly reduce the gate efficiency. In this work, we have grown quantum wells containing InAs layers using molecular beam epitaxy. The InAs layer is strained inside an InxGa1-xAs (x=0.75) quantum well, which is flanked by InxAl1-xAs  (x=0.75) barriers. By optimization of the growth, we have achieved low temperature mobilities over 300,000 cm^2/Vs at the density of 3e11 cm^-2.

We have  successfully fabricated split-gate devices to form one-dimensional channels and achieved full depletion under the gates. The point contact conductance exhibits quantized plateau and have studied spin orbit parameters in this material in gate-defined quantum wires and gated- etched quantum wires.