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Several practical issues in the development and operation of quantum-dot cellular automata (QCA) cells and systems are discussed. The need for adiabatic clocking of QCA systems and modeling of electrostatic confinement of quantum dots are presented. Experimental data on dot coupling and applications to QCA detectors in a 2-dimensional electron gas (2DEG) are presented. We report a charge detection scheme where we observe strong modulation in the detector signal, in addition to the detector exhibiting minimal effect on the dot being measured. With this investigation, we demonstrate these two key components required for QCA in AlGaAs/GaAs materials, namely dot coupling and charge-state detection.

Numerical simulations for the design of gated delta‐doped AlGaAs/GaAs quantum‐dot structures in the few‐electron regime are presented. The confining potential is obtained from the Poisson equation with a Thomas–Fermi charge model. The electronic states in the quantum dot are then obtained from solutions of the axisymmetric Schrodinger equation. Our model takes into account the effect of surface states by viewing the exposed surface as the interface between the semiconductor and air (or vacuum). Various gate configurations and biasing modes are explored. The simulations show that the number of electrons can be effectively controlled in the few‐electron regime with combined enhancement and depletion gates.

We present a study of the boundary conditions for the potential at exposed semiconductor surfaces in split‐gate structures, which views the exposed surface as the interface between the semiconductor and air. A two‐dimensional numerical algorithm is presented for the coupling between the nonlinear Poisson equation in the semiconductor(finite element method) and Laplace’s equation in the dielectric (boundary element method). The utility of the coupling method is demonstrated by simulating the potential distribution in an n‐type AlGaAs/GaAs split‐gate quantum wire structure within a semiclassical Thomas–Fermi charge model. We also present a comparison of our technique to more conventional Dirichlet and Neumann boundary conditions.

We present numerical simulations for the design of gated few-electron quantum dot structures in the Si/SiO2 material system. Because of the vicinity of the quantum dots to the exposed surface, we take special care in treating the boundary conditions at the oxide/vacuum interfaces. In our simulations, the confining potential is obtained from the Poisson equation with a Thomas-Fermi charge model. We find that the dot occupancy can be effectively controlled in the few-electron regime.