Enhanced spin-orbit scattering length in narrow AlxGa1-xN/GaN wires

The magnetotransport in a set of identical parallel AlxGa1-xN/GaN quantum wire structures is investigated. The width of the wires ranges between 1110 and 340 nm. For all sets of wires, clear Shubnikov-de Haas oscillations are observed. We find that the electron concentration and mobility are approximately the same for all wires, confirming that the electron gas in the AlxGa1-xN/GaN heterostructure is not deteriorated by the fabrication procedure of the wire structures. For the wider quantum wires, the weak antilocalization effect is clearly observed, indicating the presence of spin-orbit coupling. For narrow quantum wires with an effective electrical width below 250 nm, the weak antilocalization effect is suppressed. By comparing the experimental data to a theoretical model for quasi-one-dimensional structures, we come to the conclusion that the spin-orbit scattering length is enhanced in narrow wires.