Accurate equivalent-network modelling of GaAs/AlAs based resonant tunneling diodes with thin barrier layers

The small-signal intrinsic impedance of GaAs/AlAs based resonant tunnelling diodes with thin barriers has been measured at room temperature over the full 0-2 V bias-voltage and 0.05-40.05 GHz frequency ranges, on stable, non-oscillating devices. The classical Esaki and the quantum-inductance equivalent circuits were used to model the impedance for CAD purposes. Information about the quasibound-state lifetime against bias-voltage was extracte

Quantum point contact due to Fermi-level pinning and doping profiles in semiconductor nanocolumns

We show that nanoscale doping profiles inside a nanocolumn in combination with Fermi-level pinning at the surface give rise to the formation of a saddle-point in the potential profile. Consequently, the lateral confinement inside the channel varies along the transport direction, yielding an embedded quantum point contact. An analytical estimation of the quantization energies will be given

Two and Three Terminal Double Barrier Resonant Tunneling Devices.

viii+416hlm.;24c

A full alternative for the RTD quantum-inductance equivalent-circuit model

Under specific conditions, the small-signal series/parallel double-RC equivalent-network is a novel full mutual alternative for the resonant tunnelling diode quantum-inductance circuit model. Network optimisations to accurately match measured intrinsic impedances of stable, non-oscillating GaAs/AlAs devices, pointed at these conditions. The capacitance Cw of the series-RC branch, peaks needle-sharp at the negative dynamic conductance "maximum, indicating carrier discharge from the quantum well. The Rb Cw -time constant equals Lq Gd of the quantum-inductance model, so it is also an indication of the quasibound-state lifetime in the well. For CAD purposes, a very good RTD intrinsic impedance description in the entire bias/frequency space (0-2 V; 0.05-40.05 GHz) is obtained with frequency-independent intrinsic elements, scalable with device area

Electronic phase coherence in InAs nanowires

Magnetotransport measurements at low temperatures have been performed on InAs nanowires grown by In-assisted molecular beam epitaxy. Information on the electron phase coherence is obtained from universal conductance fluctuations measured in a perpendicular magnetic field. By analysis of the universal conductance fluctuations pattern of a series of nanowires of different length, the phase-coherence length could be determined quantitatively. Furthermore, indications of a pronounced flux cancelation effect were found, which is attributed to the topology of the nanowire. Additionally, we present measurements in a parallel configuration between wire and magnetic field. In contrast to previous results on InN and InAs nanowires, we do not find periodic oscillations of the magnetoconductance in this configuration. An explanation of this behavior is suggested in terms of the high density of stacking faults present in our InAs wires