Electron focusing with multiparallel GaAs-AlGaAs wires defined by damageless processing

Magnetoresistance modulation, resulting from electron focusing, is investigated with multiparallel GaAs-AlGaAs wires, which are defined by electron beam lithography and damageless wet-chemical etching. Distinct focusing peaks in magnetoresistance are observed, although the samples have wires longer than a ballistic mean free path, which is derived from the focusing peak intensity. Specularity coefficient p for the etched region boundary is also obtained as p≊1 from the focusing peak ratio. The mechanism limiting ballistic transport in the electron focusing condition is discussed, based on the temperature and the electron density dependence of the peak intensity.