DFG-RSF: Nonequilibrium Phenomena and Interactions in Ultrapure III-V Nanowires

• Applicants: Privatdozent Dr. Gregor Koblmüller; Privatdozent Dr. Stefan Ludwig
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 310339015

Semiconductor nanowires (SNW) are widely explored because of their flexibility in material combinations and their inherent one-dimensional geometry, which allow to tailor their physical properties in an unprecedented way and open unique opportunities in nanoelectronics, spintronics, nanophotonics and thermoelectrics. However, many applications have electronic property requirements still exceeding that of commonly available SNWs. Therefore, one main objective of this proposal is to realize ultra-pure III-V-based SNWs with intrinsically very high charge carrier mobility and/or large spin-orbit interaction.Our high quality SNWs will be particularly tailored for the second main objective of our proposal, namely to study the complex interaction dynamics of the charge carriers in SNWs being at the heart of most applications. Based on our high quality InAs-, InSb- and modulation-doped GaAs-AlGaAs core-shell SNWs, we aim at the full control of their intrinsic structural and electronic properties to enable tunability between the diffusive and ballistic transport regimes. The focus of our experiments then lies on studying many-body correlations which are enhanced in one-dimensional systems (and should be clearly visible in ballistic SNWs), the influence of spin-orbit interaction on the scattering dynamics, as well as inelastic scattering and electron-phonon interaction. Next to standard lithography techniques to contact and control the SNWs via field effect gates we will also implement intrinsically grown barriers based on axial heterostructures or superlattices, for instance to create Bragg mirrors for phonons to foster the electron-phonon interaction. Further, we will optimize ohmic contacts and create superconducting contacts by in-situ regrowth. Low resistive ohmic contacts are essential for studying the ballistic transport regime and superconducting contacts will allow us to realize unusual nonequilibrium quasiparticle distributions.To reach all these goals in this proposal we combine the core expertise of a multidisciplinary team already active in the synthesis and characterization of ultra-pure SNWs, advanced quantum transport spectroscopy and nonequilibrium nanoelectronics, as well as primary noise and scanning gate measurements. This project will provide an important progress in the MBE growth of ultra-pure and tailored SNWs, understanding of correlation effects and nonequilibrium interactions therein.

• DFG Programme: Research Grants
• International Connection: Russia
• Partner Organisation: Russian Science Foundation
• Cooperation Partner: Dr. Vadim Khrapai