Semiconductor nanostructures with short depletion length and stacked gates, patterned with an atomic force microscope

We have investigated the electronic properties of the confining potentials obtained by oxidizing the surface of Ga[Al]As heterostructures with an atomic force microscope. From magnetotransport measurements on quantum wires at liquid-helium temperatures we find an extremely small lateral depletion length of (15±5) nm as well as a specularity of the boundary scattering above 95%. Furthermore, we demonstrate that this patterning technique for in-plane gates can be combined with top gate electrodes. Sufficiently thin top gates consisting of a suitable material can be patterned as well with an atomic force microscope, and the top gate structures can be aligned with respect to the in-plane gates.