Investigation of SiGe-heterostructure nanowires

Transport characterizations of wires obtained by electron beam Lithography and etching of (100)Si/SiGe heterostructures with a high-mobility two-dimen sional electron gas are reported. Depending on the wire width, two differen t regimes for the electrical transport are found. Wires with a width larger than similar to 200 nm exhibit metallic behaviour in the quasi-ballistic r egime. The conductance dependence on the wire width reveals the presence of a depletion layer, similar to 100 nm thick, on each etched side of the wir e. The wires of width smaller than 200 nm have very large resistance and tw o different behaviours. The first kind of wires exhibit a zero-current regi on, compatible with a Coulomb blockade effect involving multiple tunnel jun ctions or with. a space-charge limited current. Other wires are insulating up to applied voltages larger than 5-6 V and their I-V characteristics can be fitted by the functional dependence of voltage-induced tunnelling of Fow ler-Nordheim type.