Towards Utilizing Scanning Gate Microscopy as a High-Resolution Probe of Valley Splitting in Si/SiGe Heterostructures

TL;DR

This paper develops a simulation framework to assess how scanning gate microscopy can be used as a high-resolution method to measure spatial variations in valley splitting in Si/SiGe heterostructures, crucial for quantum computing.

Contribution

It introduces a combined electrostatic and Schrödinger-Poisson simulation to evaluate the feasibility of using scanning gate microscopy for valley splitting measurements.

Findings

Tip-induced quantum dots can be moved away from electrodes.

Spatial translation of the tip can detect valley splitting variations.

Simulation supports the potential of SGM for valley splitting mapping.

Abstract

A detailed understanding of the material properties that affect the splitting between the two low-lying valley states in Si/SiGe heterostructures will be increasingly important as the number of spin qubits is increased. Scanning gate microscopy has been proposed as a method to measure the spatial variation of the valley splitting as a tip-induced dot is moved around in the plane of the Si quantum well. We develop a simulation using an electrostatic model of the scanning gate microscope tip and the overlapping gate structure combined with an approximate solution to the three-dimensional Schr\"odinger-Poisson equation in the device stack. Using this simulation, we show that a tip-induced quantum dot formed near source and drain electrodes can be adiabatically moved to a region far from the gate electrodes. We argue that by spatially translating the tip-induced dot across a defect in the Si/SiGe interface, changes in valley splitting can be detected.