Selection criteria for AlGaAs-GaAs heterostructures in view of their use as a quantum Hall resistance standard

Abstract

The effects of several practical properties of GaAs-AlGaAs heterostructures on the accuracy of a quantum-Hall resistance standard at a level of 1:108 are discussed. Conduction through a parallel layer, metallic current contacts, homogeneity of the electron density, sample size, and mobility are addressed. Measurements are presented concerning the influences of sample size and mobility. As regards mobility, the slope of the Hall plateau, longitudinal resistance, and critical current have been investigated. Recommendations are given on sample geometry and mobility. Feasible measurement methods are presented to check the absence of a parallel conducting layer and the quality of the contacts.