Valley splitting in Si quantum dots embedded in SiGe

Abstract

We examine energy spectra of Si quantum dots embedded into Si_{0.75}Ge_{0.25} buffers using atomistic numerical calculations for dimensions relevant to qubit implementations. The valley degeneracy of the lowest orbital state is lifted and valley splitting fluctuates with monolayer frequency as a function of the dot thickness. For dot thicknesses <6 nm valley splitting is found to be >150 ueV. Using the unique advantage of atomistic calculations we analyze the effect of buffer disorder on valley splitting. Disorder in the buffer leads to the suppression of valley splitting by a factor of 2.5, the splitting fluctuates with ~20 ueV for different disorder realizations. Through these simulations we can guide future experiments into regions of low device-to-device fluctuations.

4 pages, 4 figures

References in corpus (4)

• Controllable valley splitting in silicon quantum devices
• Valley Splitting Theory of SiGe/Si/SiGe Quantum Wells
• Spin and valley-orbit splittings in SiGe/Si heterostructures
• The Two-flux Composite Fermion Series of Fractional Quantum Hall States in Strained Si

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• Valley Phase and Voltage Control of Coherent Manipulation in Si Quantum Dots
• Coulomb interaction and valley-orbit coupling in Si quantum dots