Low-resistance, high-yield electrical contacts to atom scale Si:P devices using palladium silicide
Scott W. Schmucker, Pradeep N. Namboodiri, Ranjit V. Kashid, Xiqiao Wang, Binhui Hu, Jonathan E. Wyrick, Alline F. Myers, Joshua D. Schumacher, Richard M. Silver, Michael D. Stewart
Scanning tunneling microscopy (STM) enables the fabrication of 2-D delta-doped structures in Si with atomistic precision, with applications from tunnel field effect transistors to qubits. The combination of a very small contact area and the restrictive thermal budget necessary to maintain the integrity of the delta layer make developing a robust electrical contact method a significant challenge to realizing the potential of atomically precise devices. Here, we demonstrate a method for electrical contact using Pd2Si formed at the temperature of silicon overgrowth (250°C) minimizing the diffusive impact on the delta layer. We use the transfer length method to show our Pd2Si contacts have very high yield (>98.2%) and low-resistance (272±41 Ω-μm) in contacting mesa-etched blanket delta layers. We also present three terminal measurements of low contact resistance (96.8%).