Monolithic and Single-Crystalline Aluminum–Silicon Heterostructures

Overcoming the difficulty in the precise definition of the metal phase of metal–Si heterostructures is among the key prerequisites to enable reproducible next-generation nanoelectronic, optoelectronic, and quantum devices. Here, we report on the formation of monolithic Al–Si heterostructures obtained from both bottom-up and top-down fabricated Si nanostructures and Al contacts. This is enabled by a thermally induced Al–Si exchange reaction, which forms abrupt and void-free metal–semiconductor interfaces in contrast to their bulk counterparts. The selective and controllable transformation of Si NWs into Al provides a nanodevice fabrication platform with high-quality monolithic and single-crystalline Al contacts, revealing resistivities as low as ρ = (6.31 ± 1.17) × 10–8 Ω m and breakdown current densities of Jmax = (1 ± 0.13) × 1012 Ω m–2. Combining transmission electron microscopy and energy-dispersive X-ray spectroscopy confirmed the composition as well as the crystalline nature of the presented Al–Si–Al heterostructures, with no intermetallic phases formed during the exchange process in contrast to state-of-the-art metal silicides. The thereof formed single-element Al contacts explain the robustness and reproducibility of the junctions. Detailed and systematic electrical characterizations carried out on back- and top-gated heterostructure devices revealed symmetric effective Schottky barriers for electrons and holes. Most importantly, fulfilling compatibility with modern complementary metal–oxide semiconductor fabrication, the proposed thermally induced Al–Si exchange reaction may give rise to the development of next-generation reconfigurable electronics relying on reproducible nanojunctions.