The adsorption of AlCl₃ and incorporation of Al on Si(100) for Atomic Precision Fabrication

Superconducting semiconductors like Si, have the potential to combine aspects of spin-based qubits with superconducting devices and circuits within one material. Al-doped Si is predicted to have higher T_c than B-doped Si prompting an exploration of atomic precision (AP) compatible Al precursors. We investigated the adsorption of AlCl₃ on Si(100) with scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy, and density functional theory calculations to reveal reaction pathways of Al atom incorporation in Si. Annealing AlCl₃-exposed surface at temperatures<450°C produced three-atom-wide chlorinated aluminum chains (CACs) elongated along Si(100) dimer row. These CACs break up upon annealing at temperatures>450°C and are incorporated in Si. Subsequently, Al δ-layers were overgrown with epitaxial Si and secondary ion mass spectrometry profiling revealed an Al atom concentration > 10²⁰ cm^-3 within a ~2nm delta layer region. These results promote AlCl₃ as a viable precursor for Al doping processes of AP advanced manufacturing in Si devices.