Gating of TASE Grown InAs Nanowires for Applications in Fault-Tolerant Topological Quantum Computing

In recent years, III-V semiconductor nanowires (NWs) are attracting increasing interest in the scientific world because of the promise to provide value-added functionalities on integrated circuits by means of spintronic components, photonic circuit elements and topological quantum devices. This is mainly thanks to their high carrier mobility and saturation velocity combined with large effective g-factor. The interest of the quantum computing community in these devices stems from the possibility to eventually interface the III-V semiconductor to a superconductor. This combination unlocks the observation and control of new phenomena in mesoscopic physics. Carriers in the semiconductor may inherit certain properties of the superconductor while maintaining semiconducting characteristics such as tunable carrier density, long mean free paths, spin–orbit interaction and large g–factor. Outstandingly, the combination of gate- and magnetic field-tunability with superconductivity allows to realize a topological state of matter where Majorana Zero Modes (MZMs) are predicted to exist . In particle physics, Majorana Fermions (MFs) are (fermionic) particles which are their own antiparticles. It is still unclear if MFs exist as elementary particles, but they are likely to exist as quasiparticle excitation in certain condensed matter systems, where a MF is a quasiparticle which is its "own hole". Being its own antiparticle means that a MF must be an equal superposition of an electron and a hole state. That is why it seems natural to search for such excitations in superconducting systems, where the wavefunction of Bogoliubov quasiparticles has electron and 'hole' components intermixed.\\ Because of the peculiar nature of the creation operator describing Majoranas, the exchange of two of these quasiparticles, a process referred to as braiding, changes the state of the system, and can be used to implement logical operations on quantum bits. Even though this is already remarkable, another outstanding characteristic of these systems is that braiding of Majoranas is insensitive to local perturbations: this could be a milestone for quantum computing since many current qubit implementations are limited by decoherence effects. This work will be focused on the fabrication of high quality InAs NWs integrated on a Silicon On Insulator (SOI) wafers by means of Template-Assisted Selective Epitaxy (TASE) . We will first describe the growth process trying to highlight what makes TASE an attractive technique for both the continued downscaling of CMOS circuits and quantum computing devices. We will then discuss the issues concerning patterning of contacts and gates at nanometer scale and will characterize electrical transport in the nanowires. These devices may constitute a basis for device architectures able to perform operation. The final goal of our research is to perform fault-tolerant topologically protected quantum operations through braiding of MZMs in NWs networks.