Phase-coherent transport in InN nanowires of various sizes

We investigate phase-coherent transport in InN nanowires of various diameters and lengths. The nanowires were grown by means of plasma-assisted molecular beam epitaxy. Information on the phase-coherent transport is gained by analyzing the characteristic fluctuation pattern in the magneto-conductance. For a magnetic field oriented parallel to the wire axis we found that the correlation field mainly depends on the wire cross section, while the fluctuation amplitude is governed by the wire length. In contrast, if the magnetic field is oriented perpendicularly, for wires longer than approximately 200 nm the correlation field is limited by the phase coherence length. Further insight into the orientation dependence of the correlation field is gained by measuring the conductance fluctuations at various tilt angles of the magnetic field.Comment: 5 pages, 5 figure

Andreev reflection and strongly enhanced magnetoresistance oscillations in GaInAs/InP heterostructures with superconducting contacts

We study the magnetotransport in small hybrid junctions formed by high-mobility GaInAs/InP heterostructures coupled to superconducting (S) and normal metal (N) terminals. Highly transmissive superconducting contacts to a two-dimensional electron gas (2DEG) located in a GaInAs/InP heterostructure are realized by using a Au/NbN layer system. The magnetoresistance of the S/2DEG/N structures is studied as a function of dc bias current and temperature. At bias currents below a critical value, the resistance of the S/2DEG/N structures develops a strong oscillatory dependence on the magnetic field, with an amplitude of the oscillations considerably larger than that of the reference N/2DEG/N structures. The experimental results are qualitatively explained by taking Andreev reflection in high magnetic fields into account.Comment: 5 pages, 5 figure

Electron states, magneto-transport and carrier dynamics in modulation-doped V-groove quantum wires

We report electrical transport and photoluminescence measurements of modulation-doped GaAs/AlGaAs V-groove quantum wires. Magneto-resistance measurements clearly indicate that transport occurs through the bottom layer in wide structures, whereas sidewall quantum wells may contribute in the case of narrow structures. Strong anisotropy of the photoluminescence clearly identifies quantum wire recombination. The energy of this state is strongly dependent on the incident laser power, increasing with increasing energy, and pinning at the energy of the sidewall quantum well. The considerably reduced quantum wire electron-hole recombination rate obtained from time-resolved photoluminescence measurements, together with the density-dependence of the energy suggest that electron-hole separation occurs during the relaxation process. (C) 1998 Elsevier Science Ltd. All rights reserved