2023, Corley-Wiciak, Cedric, Richter, Carsten, Zoellner, Marvin H., Zaitsev, Ignatii, Manganelli, Costanza L., Zatterin, Edoardo, Schülli, Tobias U., Corley-Wiciak, Agnieszka A., Katzer, Jens, Reichmann, Felix, Klesse, Wolfgang M., Hendrickx, Nico W., Sammak, Amir, Veldhorst, Menno, Scappucci, Giordano, Virgilio, Michele, Capellini, Giovanni

A strained Ge quantum well, grown on a SiGe/Si virtual substrate and hosting two electrostatically defined hole spin qubits, is nondestructively investigated by synchrotron-based scanning X-ray diffraction microscopy to determine all its Bravais lattice parameters. This allows rendering the three-dimensional spatial dependence of the six strain tensor components with a lateral resolution of approximately 50 nm. Two different spatial scales governing the strain field fluctuations in proximity of the qubits are observed at <100 nm and >1 μm, respectively. The short-ranged fluctuations have a typical bandwidth of 2 × 10-4 and can be quantitatively linked to the compressive stressing action of the metal electrodes defining the qubits. By finite element mechanical simulations, it is estimated that this strain fluctuation is increased up to 6 × 10-4 at cryogenic temperature. The longer-ranged fluctuations are of the 10-3 order and are associated with misfit dislocations in the plastically relaxed virtual substrate. From this, energy variations of the light and heavy-hole energy maxima of the order of several 100 μeV and 1 meV are calculated for electrodes and dislocations, respectively. These insights over material-related inhomogeneities may feed into further modeling for optimization and design of large-scale quantum processors manufactured using the mainstream Si-based microelectronics technology.

2021, Schlipf, Jon, Tetzner, Henriette, Spirito, Davide, Manganelli, Costanza L., Capellini, Giovanni, Huang, Michael R. S., Koch, Christoph T., Clausen, Caterina J., Elsayed, Ahmed, Oehme, Michael, Chiussi, Stefano, Schulze, Jörg, Fischer, Inga A.

We examine the Raman shift in silicon–germanium–tin alloys with high silicon content grown on a germanium virtual substrate by molecular beam epitaxy. The Raman shifts of the three most prominent modes, Si–Si, Si–Ge, and Ge–Ge, are measured and compared with results in previous literature. We analyze and fit the dependence of the three modes on the composition and strain of the semiconductor alloys. We also demonstrate the calculation of the composition and strain of SixGe1 − x − ySny from the Raman shifts alone, based on the fitted relationships. Our analysis extends previous results to samples lattice matched on Ge and with higher Si content than in prior comprehensive Raman analyses, thus making Raman measurements as a local, fast, and nondestructive characterization technique accessible for a wider compositional range of these ternary alloys for silicon-based photonic and microelectronic devices.