2024/04/03 by Sukhendu Nath, Ilke Simsek Turan, Nath, S. +19
Engineering · Materials Science · Physics and Astronomy · #Diamond and Carbon-based Materials Research #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Photonic and Optical Devices #Semiconductor Quantum Structures and Devices #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2404.02748
openalex publication_date 2024/04/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Superconductivity in ultra-doped Si1-xGex:B epilayers is demonstrated by nanosecond laser doping, which allows introducing substitutional B concentrations well above the solubility limit and up to 7 at.%. A Ge fraction x ranging from 0 to 0.21 is incorporated in Si:B : 1) through a precursor gas by Gas Immersion Laser Doping; 2) by ion implantation, followed by nanosecond laser annealing; 3) by UHV-CVD growth of a thin Ge layer, followed by nanosecond laser annealing. The 30 nm and 80 nm thick Si1-xGex:B epilayers display superconducting critical temperatures Tc tuned by B and Ge between 0 and 0.6 K. Within BCS weak-coupling theory, Tc evolves exponentially with both the density of states and the electron-phonon potential. While B doping affects both, through the increase of the carrier density and the tensile strain, Ge incorporation allows addressing independently the lattice deformation influence on superconductivity. To estimate the lattice parameter modulation with B and Ge, Vegard's law is validated for the ternary SiGeB bulk alloy by Density Functional Theory calculations. Its validity is furthermore confirmed experimentally by X-Ray Diffraction. We highlight a global linear dependence of Tc vs. lattice parameter, common for both Si:B and Si1-xGex:B, with δTc/Tc ∼ 50 % for δa/a ∼ 1 %.