Defect-assisted high activation yields of bismuth donors in silicon

Bismuth donors in silicon are extremely promising candidates for applications within quantum technologies [1]. However, there are physical and technological challenges, which need to be overcome in order to achieve their potential [2]. This work considers the effect of destroying the crystalline structure of silicon and annealing conditions on the activation of Bi donors implanted to a depth of 20 nm. Secondary Ion Mass Spectrometry (SIMS) and Hall measurements were performed in order to calculate the proportion of the dopant, which was electrically active. The electrical activation yield (EAY) of implanted donors decreases with annealing temperature and achieves 60% for crystalline Si and 90% for preamorphized Si at a low thermal budget. Micro-Raman and XPS measurements show a strong correlation between annealing temperature and silicon recrystallization, which is more complex than solely considering the effect of EAY. These results demonstrate the significance in careful selection of optimal implantation and activation strategies when considering the fabrication of quantum devices based on active bismuth impurity states in silicon.

[1] G. W. Morley et al., Nat. Mater., 9, 9, 725–729, 2010

[2] A. Morello et al., Adv. Quantum Technol., 3, 11, 2000005, 2020