We report the numerical analysis of our experimental results for electron-wave propagation from a quantum point contact to a quantum wire. Our numerical method solves the boundary problem of a lattice model, and determines wave functions at an arbitrary site. This method also includes a recursive Careen s-function method. Our study found oscillations in the conductance, and magnetic suppression of those oscillations. For a simple model, we simulate the oscillations directly related to the channel number in the quantum wire. To understand the magnetic suppression, we investigate the dependence of the electron-wave propagation on the magnetic field using a realistic model. Numerical results show that a realistic rounded corner at the point-contact and a magnetic field could suppress the oscillations. We also discuss the transition from a classical skipping orbit with clear circular segments and focusing to a quantum edge state along a potential wall.

Based on work by Molenkamp et al. , we measured transfer efficiency through two quantum point contacts (QPC s) as a function of magnetic field applied perpendicularly to two-dimensional electron gas. We have reported that the results depend on the number of modes in the QPC. Previously, we had analyzed our results assuming classical mechanical trajectories of an electron. This time, to analyze our results, we studied the formulation of a Green s function using weak-magnetic-field approximation and constructed a mirror-image method in a weak magnetic field. Based on this, we calculated the position probability densities of an electron near the detector. The calculated probability densities agreed qualitatively with our results. Using quantum mechanics, we showed that our measured results equal the electron-wave dift'raction pattern in a two-dimensional electron gas. We also showed that our experiments correspond to measurements of the angular distribution of electrons injected through a QPC.

Lateral patterning of arsenic precipitates in GaAs is reported. The positions of near-surface precipitates in a GaAs layer grown by molecular beam epitaxy at low temperature are controlled by InGaAs stressors 45 nm in width covered by a SiO2 film. The stressors form a surface grating which governs the precipitate position by modulating the strain in the GaAs near the surface. Electron microscopy clearly reveals the formation of precipitates about 15 nm in diameter aligned with the stressors at a depth of ∼50 nm. It is suggested that this capability to control the position of nanometer-size metallic particles within a semiconductor could open up new possibilities for novel devices.

A study of electron-wave interference effects in a structure which is comprised of a split-gate point contact with a parallel reflector gate is reported. The structure constricts the injected electrons to a waveguide. The variation of point contact conductance with reflector voltage has novel oscillations directly related to the one-dimensional (1D) states in the waveguide. The oscillations are caused by the change in matching between a mode for the 1D waveguide state and an electron wave injected into the states. The oscillations are also found to be quenched with weak magnetic fields due to electron wave deflection.

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