Electron focusing with a double grid in AlGaAs/GaAs heterostructures

Electron focusing has been observed in single‐ and double‐grid structures. The magnetoresistance shows strong maxima and minima with values both above and below the zero field resistance. These are interpreted in terms of electron trajectories which are either backscattered from or transmitted through the grids, with a good match between the measured and calculated magnetic field values for the position of these peaks. The difference in magnetoresistance between the two structures is explained by an internal scattering mechanism which is present only for the double‐grid system.