High accuracy measurements of quantized Hall resistance ratios R/sub K/(i)/R/sub K/ (2i) for i=1 and 2 in GaAs and silicon

Indirect measurements of the quantized Hall resistance of three GaAs devices confirm that within a combined relative uncertainty (1 sigma ) of about 15 parts in 10/sup 9/, the ratio R/sub K/(i)/R/sub K/ (2i) for i=1 and 2 is exactly 2. A cryogenic current comparator bridge has been constructed to compare directly R/sub K/(2) in GaAs and R/sub K/(4) in Si with a relative uncertainty of 1 part in 10/sup 9/.<
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