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Effects of metal gate-induced compressive strain on hole mobility in Si at cryogenic temperatures
Wesolowski, Lukasz (2025) Effects of metal gate-induced compressive strain on hole mobility in Si at cryogenic temperatures.
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| Full Text Status: | Access to this publication is restricted |
| Embargo date: | 1 July 2027 |
| Abstract: | Silicon acceptor spin qubits are one of the most promising avenues to the realisation of a multi-qubit quantum computer. At the same time, design is quite complex due to the necessary lifting of the Si valence band degeneracy. As the qubit must be cooled down to cryogenic temperatures to operate, one possible approach is to use the difference in coefficients of thermal expansion of silicon and the metal gates to induce compressive strain in the Si substrate. This work investigates the relationship between hole mobility and channel strain induced by the contraction of a metal gate cooled down to 2 K, as well as the impact of device annealing time on this relationship. It is shown that in devices annealed in H2O vapour for 5 min, increasing the gate thickness from 20 nm to 60 nm results in higher hole mobility. This indicates a higher induced compressive strain. The mobility enhancement is larger along the ⟨1 1 0⟩ crystal orientation compared to the ⟨1 0 0⟩ crystal orientation, reinforcing previously documented directional dependence of holes in Si. A preferential mobility enhancement along the ⟨1 1 0⟩ crystal orientation is also observed in devices annealed in H2O vapour for 10 min, however to a much lesser extent, and with no equivalent enhancement along the ⟨1 0 0⟩ crystal orientation. This suggests that extended annealing reduces or counteracts the gate-induced strain, and that it is at least suffcient to nullify mobility enhancement along the inferior ⟨1 0 0⟩ crystal orientation. |
| Item Type: | Essay (Bachelor) |
| Faculty: | EEMCS: Electrical Engineering, Mathematics and Computer Science |
| Subject: | 33 physics, 53 electrotechnology |
| Programme: | Electrical Engineering BSc (56953) |
| Link to this item: | https://purl.utwente.nl/essays/107387 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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