EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

We present a combined experimental and theoretical effort to fabricate NiSi$_2$-Si interfaces in nanowire structures and to understand the resulting Schottky barrier height, which is essential for the subsequent transport properties.
The NiSi$_2$-Si interfaces were created using silicidation of top-down fabricated silicon nanowires. Silicidation was performed using either rapid thermal or flash-lamp annealing. The latter method enables better control over the silicidation length. The crystal structure of the interface was characterized using high-resolution (scanning) transmission electron microscopy. Similar interface structures were observed for both silicidation methods. In addition, we have performed density functional theory calculations to calculate the stability of NiSi$_2$-Si interfaces with different orientation. In accordance with the fabricated structures, the {111} interface orientation is found to be the most stable [Khan2019, Fuchs2020].
The effective Schottky barrier heights of the fabricated structures were extracted from temperature-dependent current-voltage measurements. The extracted Schottky barrier heights for electrons were a few tens of meV higher than that of holes. Furthermore, density functional theory calculations of the physical Schottky barrier height for extended interfaces were performed for various NiSi$_2$-Si interfaces. We show that the Schottky barrier heights differ by several hundreds of meV between different interfaces. Applying external strain changes the silicon band gap and thus changes the absolute values of the Schottky barrier heights. The ratio between the Schottky barrier heights for electrons and holes is also modified via the external strain, which shows a different behavior depending on the interface. Therefore, by using a suitable combination of the interface orientation and strain, devices can be optimized without using additional doping.

References:
[Khan2019] M.B. Khan et al., Applied Sciences 9, 3462 (2019); https://doi.org/10.3390/app9173462
[Fuchs2020] F. Fuchs et al., Journal of Applied Physics 128, 085301 (2020); https://doi.org/10.1063/1.5143122