Noise and transport study of semiconductor microstructures

In this work an experimental study of electrical noise and transport near the metal-to-insulator transition and in the insulating regime of conduction of semi-conductor microstructures is presented. It is demonstrated that by studying the behaviour of noise important information can be obtained about the details of electron kinetics in microstructures. Moreover, it is shown that noise measurement is a sensitive tool for investigations of the effect of electron-electron interactions in the localised regime of conduction. By employing time dependent measurements of the resistivity of the two-dimensional electron gas in silicon, the presence of a narrow impurity band in the vicinity of the conducting channel is detected. This observation confirms that the unexpected metal-to-insulator transition in our 2D structures is a result of non-interacting electron transport. A significant part of this thesis deals with experimental studies of shot noise in the insulating regime. When transport is dominated by phonon-assisted hopping via many localised states, it is shown that shot noise is generally suppressed compared with its classical non-interacting value. The suppression factor is determined by the geometry of the studied structures, electron density and applied electric field. When resonant tunnelling through individual localised states is the main transport mechanism, the effect on shot noise of the Coulomb interaction between two localised states is studied. It is found that correlated electron transport in this case leads to an enhancement of shot noise. With decreasing temperature, resonant tunnelling across a short-length potential barrier becomes phase coherent. In this regime unusual features of shot noise are observed near the onset of the tunnelling current and their possible origins are discussed. (author)SIGLEAvailable from British Library Document Supply Centre- DSC:DXN055377 / BLDSC - British Library Document Supply CentreGBUnited Kingdo