Lifting of Spin Blockade by Charged Impurities in Si-MOS Double Quantum Dot Devices

TL;DR

This paper investigates how charged impurities in Si-MOS double quantum dots lift spin blockade, combining theory and experiments, and suggests design modifications like overlapping gates to mitigate this issue.

Contribution

It identifies stray positive charges as a cause of spin blockade lifting and proposes device design strategies to reduce this effect.

Findings

Charged impurities induce levels that lift spin blockade.

Overlapping gates can mitigate impurity effects.

Experimental and theoretical evidence supports these conclusions.

Abstract

One obstacle that has slowed the development of electrically gated metal-oxide-semiconductor (MOS) singlet-triplet qubits is the frequent lack of observed spin blockade, even in samples with large singlet-triplet energy splittings. We present theoretical and experimental evidence that the cause of this problem in MOS double quantum dots is the stray positive charges in the oxide inducing accidental levels near the device's active region that allow spin blockade lifting. We also present evidence that these effects can be mitigated by device design modifications, such as overlapping gates.