Quantum Switching Modeling and Optimization of a Metal-Oxide-Semiconductor Gated Y-Shaped Structure

Using Silvaco Atlas codes achieving 3D simulation by combining a 2D Schrodinger-Poisson electrostatic solver and non-equilibrium Green’s function (NEGF) transport simulator, we demonstrated low-power switching in a gated Y-shaped one-dimensional ballistic waveguides prepared from Al-free InGaAs/ GaAs quantum well. We have evaluated current switching in the devices as a function of modulation doping and temperature. Modulation doping was implemented symmetrically around the quantum well with 5nm spacer layers to match the experimentally fabricated test structures. To verify the solver is correctly treating quantum transport, simulations were executed for different doping levels to control filling of the first few 1D subbands. The resulting conductance showed the expected stair-like profile with the quantum steps of 7.75x10^-5 S. We demonstrated the current switching between branches of the Y-shaped waveguide at gate voltage as low as 10 mV with 1 mV bias applied to the waveguide, and compared these results to estimates based on the overlap of wavefunctions of the stem and the branches. Notably, the most efficient switching occurs when only the first subband of the stem is occupied with the second subband starting to fill near the junction. In this case, the conduction 1D subband discontinuity at the junction results in the first energy level of the branches matching the second partially filled subband of the stem. This results in one order of magnitude ballistic current steering between the degenerate (metallic) semi-conductor 1D branches at about 6 mV at low temperature.