Fabrication of GaAs/AlGaAs based quantum resistance standards

This paper reports on the progress in the development of fabrication process of metrological quantum Hall effect (QHE) devices from GaAs/AlGaAs two-dimensional electron gas (2DEG), including single Hall bar quantum resistance standards, Quantum Hall Arrays Resistance Standards (QHARS) and other specific devices (quantum Wheatstone bridges) dedicated to very high-accuracy quantum Hall resistance comparisons and QHE universality tests. Single Hall bars have been obtained exhibiting very low resistance ohmic contacts (<;0.3 Ω), low longitudinal resistances (<;10 μΩ), bearing high biasing currents (up to 250 μA), hence allowing the Hall resistance to be measured exactly quantized on the V = 2 plateau at the expected value within an uncertainty lower than 2 parts in 10
⁹
. Besides, crucial steps have been overcome in the sophisticated fabrication process of QHARS.