Journal Publications

The article deals with the modeling of gate voltage controlled resonant tunneling transport in a complementary-metal–oxide–semiconductor (CMOS) compatible double quantum dot channel nanowire field-effect-transistor (FET). Appropriate applied voltages at two separate gates, gate-1 and gate-2 of the device form two voltage-tunable quantum dots underneath the gates, within the nanowire channel. The quantum dot eigenstates are tuned by varying the applied gate voltages to enable voltage-modulated resonant tunneling transport. Such transport is modeled by employing a Schrödinger-Poisson self-consistent framework using non-equilibrium Green’s function (NEGF) formalism. Electron–phonon scattering within the nanowire channel is also considered. The transfer characteristics exhibit multiple current thresholds in the range of 10^(−4) uA/um – 1 uA/um due to resonant tunneling. The phonon scattering is observed to significantly depend on nanowire geometry and applied gate voltages, with tunneling dominated quasi-ballistic transport occurring at higher gate voltages. Also, steep sub-threshold slopes of 30 mV/decade–8 mV/decade range and transconductance in the range of 10^(−7) uS/um – 1 uS/um at room temperature are obtained by varying the nanowire diameter in the range of 20 nm – 5 nm. Therefore, such device architecture exhibits significant potential for achieving multi-current thresholds in a CMOS compatible architecture at room temperature.

This work investigates the material-dependent charge qubit performance of a gate voltage-induced double-quantum-dot gate nanowire channel field-effect transistor (DQD-NWFET) device through charge stability, Bloch sphere coverage, anti-crossing energy, and dephasing time. In this device, voltages at two localized gates along the nanowire channel create two quantum dots in series, which are further tuned by these voltages for the relevant qubit operations. To understand the material-dependent performance of the device, a self-consistent Schrodinger-Poisson framework coupled to non-equilibrium Green’s function formalism is developed. The study indicates that the charge qubit performance of the device significantly depends on the transport effective mass, with slight dependence on nanowire permittivity. It is observed that the increase in transport effective mass leads to sharpening of the “hyperbolic” nature of the charge stability diagram, along with a significant reduction in anti-crossing energy and Bloch sphere coverage. Consequently, anti-crossing energy in the range of 3–25 meV and dephasing time in the range of 25–130 ns can be achieved by varying the transport effective mass and nanowire permittivity from 0.04 to 0.10 and 10–16, respectively. The performance of the device is further studied for specific nanowire materials by taking into account the appropriate material parameters. Therefore, this study enables material engineering of nanowire FET devices for realizing superior charge qubit performance.