Quantum resistance standards with double 2DEG

We have developed a new generation of quantum Hall array resistance standards (QHARS) obtained from GaAs/AlGaAs heterostructures with double two-dimensional electron gases (2DEGs) grown by the metal-organic vapor phase epitaxy process. We have achieved the fabrication of such a multilayer system with well matched carrier density and mobility of the two 2DEGs and characteristics required for metrological use. This technological achievement allowed calibrations in terms of a quantized Hall resistance (R/sub K//2 on i=2 plateau) of a single Hall bar (R/sub K//4) and 50 Hall bars placed in parallel by triple connections QHARS129 (R/sub K//200). In both cases relative deviations of their Hall resistance from their expected nominal value are found lower than eight parts in 10^9, corresponding to the measurement uncertainty (1(sigma)). These measurements were performed on QHARS129 samples supplied by higher measuring currents up to 2 mA at 1.3 K.