Flux periodic oscillations and phase-coherent transport in GeTe nanowire-based devices

Despite the fact that GeTe is known to be a very interesting material for applications in thermoelectrics and for phase-change memories, the knowledge on its low-temperature transport properties is only limited. We report on phase-coherent phenomena in the magnetotransport of GeTe nanowires. From universal conductance fluctuations measured on GeTe nanowires with Au contacts, a phase-coherence length of about 280 nm at 0.5 K is determined. The distinct phase-coherence is confirmed by the observation of Aharonov–Bohm type oscillations for parallel magnetic fields. We interpret the occurrence of these magnetic flux-periodic oscillations by the formation of a tubular hole accumulation layer. For Nb/GeTe-nanowire/Nb Josephson junctions we obtained a critical current of 0.2 μA at 0.4 K. By applying a perpendicular magnetic field the critical current decreases monotonously with increasing field, whereas in a parallel field the critical current oscillates with a period of the magnetic flux quantum confirming the presence of a tubular hole channel.

Semiconductors

Semiconductors are introduced. Hole kinematics are deduced. Effects of doping giving donor and acceptor levels are surveyed: silicon and AlxGa1−xAs are used as exemplars. Diode function is interpreted in terms of carrier densities. Zener diodes. Optical response, diode photon detectors and photovoltaic cells. Limitation of LEDs to direct bandgap materials is explained. The operation of ultrafast Silicon MOSFETs and 100GHz GaAs HEMTs is described. The conditions for quantum effects at the mesoscopic scale examined: the influence of coherence length, Fermi wavelength and mean free path. Cryogenic quantum point contact devices, the quantum of conductance and Landauer’s equation surveyed. Ballistic and diffusive transport contrasted. Coulomb blockade is described. Observation at cryogenic temperatures of quantum interference in disordered conducting material. Universal conductance fluctuations are presented.

Universal conductance fluctuations and phase-coherent transport in a semiconductor Bi2O2Se nanoplate with strong spin–orbit interaction

Universal conductance fluctuations and spin–orbit interaction induced reduction in fluctuation amplitudes have been observed for the first time in the magnetotransport measurements of a Bi2O2Se nanoplate.