Semiconductor nanowires as building blocks for quantum devices

Semiconductor nanowires are versatile building blocks for the design of future electronic devices. Among the many possible materials, InN is particularly interesting because of its low energy band gap and its high surface conductivity. At low temperatures electron interference effects often play an important role in the transport characteristics of nanostructures. We studied the electronic transport of InN nanowires grown by plasma-assisted molecular beam epitaxy. The wires had a diameter ranging from 40 nm to 130 nm and a length of approximately 1 μm. Information on the phase-coherent transport was gained from the measurement of universal conductance fluctuations. It was found that at low temperatures phase-coherence is maintained in the complete wire structure, which is an important prerequisite for quantum devices. For nanowires comprising a very small diameter of approximately 40 nm pronounced flux-periodic oscillations in the magneto-conductance were observed. This effect is attributed to the formation of coherent circular quantum states on in the tube-like surface electron gas.