Selected Area Growth Semiconductor/Superconductor Hybrid Topologically Protected Nanowire-based Networks and Planar Heterostructures (e.g. 2DEGs and 2DHGs)

Abstract

Semiconductor spin qubits have become an exciting avenue for scalable quantum computers, but the nanodevices that control them require further investigation to bring this excitement to fruition. By fine-tuning the strain on these devices the g-factor can be maximized and make it easier to control spin rotations for qubit gate operations, and increase spin qubit lifetimes. First, we analyzed multiple 2D electron gas (2DEG) devices, based on top down nanoengineering, using a Transmission Electron Microscope to probe into how factors such as crystal structure, strain, and composition affecting them. In Si/SiGe planar heterostructure 2DEG devices, we noted the exceedingly low density of dislocations for thinner quantum wells, as well as a larger compression imposed onto them. Secondly, we studied an alternative type of quantum devices based on planar Germanium nanowires, which follows a bottom up approach. In this latter case, strain was relieved through dislocations along the interface between the Ge wire and the Si substrate, which is thought to have been caused by the rough interface formed during fabrication as Si migrated into the Ge wire. Results for these devices have already shown better scattering properties in the heterostructures and longer coherence lengths in nanowires [RTM+22]. While the results for the nanowires already look promising, further engineering is being performed to maximize the device’s potential and finally achieve 2D Hole Gas devices (2DHG).