Exploring the effect of band-edge states at the MOS interface on quantum devices: A simulation study using transistor's subthreshold swing as the trigger

Charge noise induced by carrier trapping/de-trapping causes spin dephasing in silicon-based spin qubits. The defect states at the MOS interface are considered the most likely candidates for the noise source, a subject to which many researchers are dedicated to clarifying. Meanwhile, it has been reported that the band-edge states originating from the MOS interface defects induce noise in the cryogenic operation of MOSFETs. A key device parameter is the subthreshold swing (SS), which sensitively reflects the interface-related band-edge states.

We explore the source of charge noise in silicon spin qubits, focusing on the band-edge states as a potential candidate, and leveraging the SS in MOSFET operation as a trigger. In this presentation, we report a theoretical investigation capturing the distribution of the interface-related band-edge states, which can reproduce the experimental temperature dependence of the SS. This knowledge allows a quantitative discussion of the relationship between the noise and band-edge states, which will also be discussed in this talk. These findings suggest that improving the Si/SiO₂ interface quality to reduce the band-edge states is crucial for minimizing noise in MOS-based quantum devices.