Simulations of gate-biased illumination in Si/SiGe quantum dots to achieve low and uniform operating voltages

The ability to tune semiconductor quantum dot devices using low and uniform gate voltages is a key requirement for scalability. However, this can be challenging in real devices, since gate voltages tend to drift slowly over time. A well-known method for mitigating such gate-voltage variability is to modify the local distribution of trapped charge at the oxide-semiconductor interface by illuminating with near-infrared light. More recently, in Si/SiGe quantum dots, it has been shown that the interface charge can be better controlled by biasing the gates during illumination. Here, we present simulations to explain the rearrangement of charge and determine the pinch-off voltages obtained after illuminating with given bias voltages. Our simulations use the MaSQE (Modeling and Simulation for Quantum Exploration) self-consistent Schrödinger-Poisson code. In the talk, we first describe the simulation procedure and then compare our theoretical results to experimentally measured turn-on voltages in a triple-dot device, obtaining excellent agreement. This correspondence implies that the device may be reset to a desired operating point, even after voltage drifts or uncontrolled charging events. Experimentally, we show that the triple-dot can be tuned to the (1,1,1) charge configuration using gate voltages that are low and uniform for all plunger and tunnel-barrier gates. This provides a proof-of-concept demonstration that biased illumination can provide a key tool for scaling up quantum dot qubit devices.