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

One obstacle that has impeded the development of electrically gated MOS singlet-triplet qubits is the lack of observed spin blockade, where the tunneling of a second electron into a dot is fast when the two-electron state is a singlet and slow when the state is a triplet, even in samples with large singlet-triplet energy splittings. We present theoretical and experimental evidence that the cause of this commonly exhibited problem in MOS double quantum dots is the presence of stray positive charges in the oxide layer that induce accidental dots near the device’s active region that allow spin blockade lifting. We also present evidence that these effects can be mitigated with device design modifications.

This work was supported by ARO (W911NF1210607, W911NF1410346, W911NF12R0012, W911NF1210609, W911NF1710257), NSF (IIA1132804, OISE1132804), the Department of Defense under Contract No. H9823015C 0453, and MINECO (Spain) FIS201233521 and FIS201564654P. The authors acknowledge support from the Vannevar Bush Faculty Fellowship program sponsored by the Basic Research Office of the Assistant Secretary of Defense for Research and Engineering and funded by the Office of Naval Research through grant N000141510029.