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Germanium Quantum Technology Solutions

01 /What can CMOS technology do for quantum computing? 02 /Semiconductor devices and scaling with industrial approach 03 /Semiconductor foundry facilities: the good and the bad for qubits 04 /IMEC's latest qubit developments 05 /Summary and outlook 06 /Semiconductors for spin qubits 07 /Germanium quantum wells on silicon 08 /Germanium quantum wells on silicon-germanium 09 /Growth methods 10 /Characterization techniques 11 /Electrical characterization of germanium quantum wells 12 /Fabrication of H-FET 13 /Semiconductor qubits: vision and challenges 14 /Quantum materials 15 /Quantum dot qubits and their operation 16 /Types of quantum dot qubits 17 /Qubit Readout 18 /Qubit Control 19 /Qubit Coherence and Fidelity 20 /Multi-qubit control and quantum algorithms 21 /Quantum links and scaling 22 /Physics of holes 23 /Hole spin qubits 24 /Introduction to electronics for quantum computing 25 /Room temperature electronics 26 /Cryogenic qubit chip carriers 27 /Contribution to IGNITE 28 /Quantum Control Stack for Spin Qubits 29 /What is auto-tuning? 30 /Neural network tuning 31 /Navigating charge stability diagrams 32 /Experimental implementation 33 /Towards universal quantum algorithms 34 /Classical error correction 35 /Quantum error correction 36 /Progress and challenges 37 /Introduction to quantum algorithms 38 /The first algorithms 39 /Quantum annealing 40 /Quantum Machine Learning

Characterization techniques

True or False: Geometrical Phase Analysis (GPA) carried out in TEM measurements of the Ge QW with respect to a reference point in the SiGe barrier indicates an in-plane strain close to 0. This means that the QW is fully relaxed.

False.

It actually indicates that the Ge QW has the same in-plane lattice constant as the SiGe barrier i.e. that the QW is fully strained. The strain in a GPA measurement is not defined in terms of the measured lattice parameter and the expected natural lattice parameters of the material but rather the measured lattice parameter as compared to a reference measured in another part of the image. In order to arrive at the true strain values, knowledge of the material is required (the composition can be found e.g. from electron energy loss spectroscopy if not from XRD or SIMS). In addition, the thin TEM section may elastically relax, further complicating the relationship between the measured strain values and the actual strain in the 2d QW.

See for example figures S5 and S6 in the Supplementary Information of Daniel Jirovec, Andrea Hofmann, Andrea Ballabio, Philipp M. Mutter, Giulio Tavani, Marc Botifoll, Alessandro Crippa, Josip Kukucka, Oliver Sagi, Frederico Martins, Jaime Saez-Mollejo, Ivan Prieto, Maksim Borovkov, Jordi Arbiol, Daniel Chrastina, Giovanni Isella, and Georgios Katsaros. A singlet triplet hole spin qubit in planar Ge. Nature Mater. 20 (8) 1106--1112 (2021). https://www.nature.com/articles/s41563-021-01022-2