Understanding the Electronic Transport of Al–Si and Al–Ge Nanojunctions by Exploiting Temperature-Dependent Bias Spectroscopy

• Published in: ACS applied materials & interfaces 2024-04, Vol.16 (15), p.19350-19358
• Main Authors: Behrle, Raphael, Murphey, Corban G. E., Cahoon, James F., Barth, Sven, den Hertog, Martien I., Weber, Walter M., Sistani, Masiar
• Format: Article
• Language: English
• Subjects: Functional Nanostructured Materials (including low-D carbon); Physics
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.3c18674

Understanding the electronic transport of metal–semiconductor heterojunctions is of utmost importance for a wide range of emerging nanoelectronic devices like adaptive transistors, biosensors, and quantum devices. Here, we provide a comparison and in-depth discussion of the investigated Schottky heterojunction devices based on Si and Ge nanowires contacted with pure single-crystal Al. Key for the fabrication of these devices is the selective solid-state metal–semiconductor exchange of Si and Ge nanowires into Al, delivering void-free, single-crystal Al contacts with flat Schottky junctions, distinct from the bulk counterparts. Thereof, a systematic comparison of the temperature-dependent charge carrier injection and transport in Si and Ge by means of current-bias spectroscopy is visualized by 2D colormaps. Thus, it reveals important insights into the operation mechanisms and regimes that cannot be exploited by conventional single-sweep output and transfer characteristics. Importantly, it was found that the Al–Si system shows symmetric effective Schottky barrier (SB) heights for holes and electrons, whereas the Al–Ge system reveals a highly transparent contact for holes due to Fermi level pinning close to the valence band with charge carrier injection saturation due to a thinned effective SB. Moreover, thermionic field emission limits the overall electron conduction, indicating a distinct SB for electrons.