Abstract:
Historically, in measurements of electron transport in disordered systems, an Arrhenius Hall carrier density has never been observed alongside an Arrhenius conductivity, when the Fermi level is below a mobility edge. This has long been an issue with respect to claiming observation of conductivity via activation to a mobility edge. In this work, an Arrhenius conductivity and Arrhenius Hall carrier density have been observed alongside one another. Measurements were made of a two-dimensional electron gas hosted in a gated GaAs/Al0.33Ga0.67As heterostructure. Furthermore, in the regime of Arrhenius conductivity and Arrhenius carrier density, the mobility is shown to be independent of the position of the Fermi level below the mobility edge. A transition between carrier density and mobility dominating the resistivity temperature dependence has been observed, as Fermi level is varied. Measurements were also made in the Efros-Shklovskii hopping transport regime. The results support other works which claim a Hall mobility of the same form as the conductivity, but with a different characteristic temperature.
Bio:
Robert Carroll studied for his doctorate at University College London, under the supervision of Michael Pepper. The project focused on localisation in disordered electronic systems. The Hall effect, in the case that the Fermi level is below a mobility edge, and the breakdown of the quantum Hall effect were studied using GaAs/AlxGa1-xAs heterostructures.
Following this, he joined Julie Euvrard’s group in February this year. Here his research will focus on the Hall effect with mixed hopping and band-like transport in organic semiconductors.