Engineering Si-Qubit MOSFET: Quantum-Electrostatic Integration at Cryogenic Temperatures

This study employs advanced phase-field modeling to investigate Si-based qubit MOSFETs, integrating electrostatics and quantum mechanical effects. We adopt a comprehensive modeling approach, utilizing full-wave treatment of the Schrödinger equation solutions, coupled with the Poisson equation at cryogenic temperatures. Our analysis explores the influence of interface traps on quantum dot (QD) barrier heights, affecting coupling due to tunneling. A wider trap distribution leads to the decoupling of QDs. Furthermore, the oscillations in the transmission and reflection coefficients increase as the plunger gate (PG)/barrier gate (BG) length is increased, reducing the coupling between the QDs. By optimizing PG and BG dimensions, spacer configurations, and gap oxide lengths, we enhance control over quantum well depths and minimize unwanted wave function leakage. The modeling algorithm is also validated against the experimental data and can accurately capture the oscillations in the ${I}_{d}$ – ${V}_{\text {gs}}$ caused by the Coulomb blockade at cryogenic temperature.