Selective Growth and Characterization of InAs and InSb Nanostructures

Overview & Synopsis

In the landscape of electronic device fabrication, the semiconductor compounds indium arsenide (InAs) and indium antimonide (InSb) have emerged as materials of significant interest for high-speed telecommunications and infrared optoelectronics. More recently, their excellent electron transport characteristics, characterized by high mobility and strong spin-orbit coupling, render them highly conducive for applications that exploit quantum transport phenomena. However, their deployment is often hampered by the lattice mismatch they possess with conventional III-V substrates, making them defective. This thesis proposes a solution for fabricating good-quality in-plane InAs and InSb nanostructures, using selective area growth by molecular beam epitaxy in SiO2 apertures.A structural and morphological study of InAs and InSb two-dimensional layers and nanowires on GaAs and InP substrates oriented along the [001] and [111] directions has been carried out. The optimization of the growth parameters led to the fabrication of continuous and faceted planar nanostructures with minimized threading defects. These systems were then studied by four-tip scanning tunnelling microscopy in ultra-high vacuum, a technique that eliminates the need for electrode fabrication to characterize the transport properties. The comparison of transport in surface-reconstructed InAs nanowires and core-shell InAs/GaSb nanowires revealed the benefits of embedding the InAs nanowires to significantly increase the electron mobility in the nanowires.Unlike the InAs nanowires, which can be protected by a thin layer of arsenic to preventtheir surface oxidation during their transfer to air, there is no effective protection for InSb.The final part of the thesis therefore focuses on characterizing the deoxidation of InSb (001) and (111) surfaces using a combination of Raman spectroscopy and scanning tunnelling microscopy. This latter study paves the way for subsequent measurements of the transport in InSb nanowires by four-tip scanning tunnelling microscopy.In conclusion, the structural and electronic quality of the InAs and InSb nanowires produced in this work is compatible with the ballistic transport regime. These results lay down the foundations for the fabrication of the more complex III-V structures, highly prized for thedesign of quantum devices.