Hall effect in macroscopic ballistic four-terminal square structures

The Hall effect is studied for 10–30-μm size ballistic four-terminal square structures fabricated on an ${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As-GaAs high-mobility modulation-doped wafer. On this scale, four-terminal square structures with sharp aperture corners are possible. The Hall resistance is not quenched and is larger than the classical linear value in a low magnetic field. It has periodic peaks corresponding to electron focusing when the terminals are narrow, and a broadening of these peaks makes a plateaulike structure when the terminals are wide.