A new approach to simulating electron densities obtained in scanning gate microscopy of Si/SiGe quantum dot devices

To advance the understanding of what limits the valley degree of freedom in silicon-based spin qubits, a cryogen-free scanning gate microscope (SGM) has been demonstrated [1]. Along with probing the microscope’s potential to enable spatial mapping of the valley splitting in Si/SiGe quantum dot (QD) devices, semiconductor quantum device simulations were implemented [2]. However, these simulations assume a 2D device gate geometry and omit the role of the tip bias and the 3D overlapping gate architecture [3] in the charge occupation of the QD device. Here, we present recent efforts on using domain decomposition methods to combine an electrostatics model of the tip bias and the 3D overlapping gate structure with an approximate solution to the 3D Schroedinger-Poisson equation [4]. These efforts allow us to explore the effect of the tip bias of the microscope on the electron density of a Si/SiGe quantum dot and compare with experimental data.

[1] Oh et al., AIP Adv. 11, 125122 (2021)

[2] Denisov et al., Nano Lett. 22, 12, 4807 (2022)

[3] Zajac et al., Phys. Rev. App. 6, 054013 (2016)

[4] Anderson et al., J. Comput. Phys. 228, 4745 (2009)