Design guidelines for Si metal-oxide-semiconductor and Si/SiGe heterostructure quantum dots for spin qubits

Si-based spin qubits are promising due to their long decoherence time and the compatibility with state-of-the-art semiconductor technology and have been demonstrated using quantum dots (QDs) to host single electrons for spin manipulation. In this work, we simulate the electrostatics and quantum transport properties of quantum dots on a Si metal-oxide-semiconductor platform and a Si/SiGe heterostructure. We investigate the effects of gate configurations and the SiGe spacer thickness on device characteristics, such as gate capacitances, Coulomb blockade, and charge stability. For a single quantum dot, placing its barrier gates (BGs) under the plunger gate improves the charge stability, while swapping the positions of those gates reduces the effects of the barrier gate biases on the charge stability. A thicker SiGe spacer further suppresses the effects of the barrier gate biases on the charge stability for quantum dots on the Si/SiGe heterostructure but leads to stronger crosstalk between neighboring quantum dots. Wider barrier gates can help to mitigate the crosstalk effects for multiple quantum dots. These findings provide key insights into the optimization of the gate configurations and material selection to improve the charge stability and minimize the crosstalk by different gates for future development of scalable Si-based quantum dots.