Electrostatic Simulation of Bi-Implanted Silicon Single-Electron Transistor Nanodevices

In this research, we create an electrostatic model of a bismuth-implanted silicon nanodevice consisting of a single-electron transistor (SET) and a number of gates. The SET is used for precise charge sensing of bismuth (donor) atoms, which is needed to use them as qubits. After extracting capacitance data from experimental measurements of the nanodevice, we refine the model’s geometry to better represent the fabricated device, revealing potential misalignment of two fabrication layers in the order of 10 nm. Next, we perform donor triangulation by varying simulated donor position and matching simulated capacitances to experimental data. We are able to estimate the position of a donor within a region of approximately 10 nm × 10 nm — a factor of 400 times more accurately than the predicted donor implantation window prior to simulations. Additionally, we conduct strain simulations, and, in conjunction with triangulation results, identify a potential unintentional strain-induced quantum dot in the vicinity of the SET. We conclude that electrostatics simulations can be used to significantly enhance knowledge of donor positions, though they do not suffice for prediction of donor depth within the silicon substrate.