Using a novel growth mechanism on patterned high-index GaAs (311)A substrates we have developed a new concept to fabricate quantum wires and quantum dots as well as coupled quantum wire–dot arrays by molecular beam epitaxy. The combination of self-organized growth with lithographic patterning and the assistance of atomic hydrogen produces these quasi-planar lateral nanostructure arrays with unprecedented uniformity in size and composition and with controlled positioning on the wafer. The sought for one- and zero-dimensional nature of these quantum wire and quantum dot arrays manifests itself in the superior optical properties. To functionalize our lateral semiconductor quantum wire and quantum dot arrays with the properties of magnetic thin films, epitaxial Fe layers have been grown on GaAs (311)A. Defect free Fe layers are obtained on As-saturated GaAs surfaces. The large electrical conductivity of thin Fe layers indicates reduced Fe–GaAs interface compound formation. An unusual in-plane spontaneous Hall-effect is observed in these epitaxial Fe layers of reduced symmetry.