Manipulating Superconductivity in Ultra-Doped Silicon and Germanium

Jerrold A. Floro
Department of Materials Science and Engineering, School of Engineering and Applied Sciences, UVa

Jongsoo Yoon
Department of Physics, College of Arts and Sciences, UVa

Recently, it was discovered that Group IV semiconductors exhibit superconductivity when the host material is doped far beyond the equilibrium solubility. Realization of robust superconductivity that can be controlled by doping of the host semiconductor is truly fascinating, and could open up a new horizon in semiconductor-based device paradigms. However, the superconductivity observed so far is fragile, and the important material parameters that could enhance the superconductivity are not clearly identified. Furthermore, the nature and the mechanism of the supesrconductivity are not known. By combining our expertise in extreme semiconductor processing (Floro), and superconductivity (Yoon), we propose to push the limit of material synthesis to optimize the superconductivity and to enhance the understanding of the superconductivity in ultra-doped semiconductors.  Our efforts will focus on exploiting lattice mismatch strain in alloys of GeSi grown on Si, combined with precise kinetic control via hyperthermal molecular beam epitaxy, to synthesize highly supersaturated electronic dopant concentrations (including B, Ga and Al). The electronic properties of the synthesized material will be studied by Hall measurement, dc transport measurement down to ~ 20 mK and magnetic fields as high as 11 T, and nonlinear transport and magnetoresistance measurements. This NanoStar seed grant will allow us to demonstrate our capability to push the limit in the material synthesis and to enhance the understanding of the superconductivity in ultra-doped Group IV epitaxial films.