Fabrication and characterization of InAs nanowire-based quantum dot structures utilizing buried bottom gates

Semiconductor nanowires can be utilized to create quantum dot qubits. The formation of quantum dots is typically achieved by means of bottom gates created by a lift-off process. As an alternative, we fabricated flat buried bottom gate structures by filling etched trenches in a Si substrate with sputtered TiN, followed by mechanical polishing. This method achieved gate line pitches as small as 60 nm. The gate fingers have low gate leakage. As a proof of principle, we fabricated quantum dot devices using InAs nanowires placed on the gate fingers. These devices exhibit single electron tunneling and Coulomb blockade.