Mesoscopic coherence phenomena in semiconductor devices

Abstract

Semiconductor devices have several attractive properties which make them useful in the study of electronic coherence phenomena such as universal conductance fluctuations. The use of gated devices allows the Fermi level, and thus the electronic wavelength, to be adjusted in order to study energy correlation effects. The two-dimensional electron gas formed beneath the gate can be tilted with respect to the magnetic field to reveal that the field correlation length of the fluctuations obeys a cosine law. This strongly suggests that the fluctuations are caused by quantum interference in the same way that the Aharonov-Bohm effect arises in metallic rings. The energy range over which electrons are correlated in these materials is generally larger than in metals. This allows one to study these conductance fluctuations at much higher temperatures than are feasible in metallic conductors. For the same reason, substantially larger source-drain voltages can be applied to observe asymmetry and nonlinear effects in the conductance.