Graphene Quantized Hall Array Star-Mesh Network for Improved Bridge Sensitivity

Our recent work on implementing a 1 GΩ starmesh graphene quantum Hall array resistance standard (QHARS) using a dual-source bridge has comparable measurement results with uncertainties of the same order of magnitude to the wellestablished measurements based on scaling from a single Hall bar to the MΩ and GΩ ranges, while also revealing certain limitations of the symmetric star-mesh device. The breakdown current in the first branch with few Hall elements, and a low output-to-ground resistance of this QHARS compared to that of the measured standard resistor decreased the bridge sensitivity. These two issues may be overcome by adding a sufficient number of Hall elements at the first and the last branch of the QHARS. The performance of the bridge measurement was then analyzed using a Spice model to replicate the behavior of a star-mesh device in the quantized state. The simulations were performed with a maximum input voltage that the device can withstand. Several improved designs for 1 GΩ, as well as new designs for 10 GΩ QHARS devices, are reported, with device output resistances falling within 500 µΩ/Ω of nominal.