Fabricating tunable semiconductor devices with an atomic force microscope

We fabricated quantum wires of different geometries in Ga[Al]As heterostruc tures by local oxidation of the semiconductor surface with an atomic force microscope. By magnetotransport measurements at low temperatures on these w ires the electronic width is determined and compared to the geometrical wid th. An extremely small lateral depletion length of the order of 15 nm and a high specularity of the scattering at the confining walls is found. Furthe rmore, we demonstrate experimentally that these quantum wires can be tuned by a combination of in-plane gates and top gates. (C) 1999 American Institu te of Physics. [S0003-6951(99)02134-8].