Precision Measurement of 1 MΩ Quantum Hall Resistance Array

We present preliminary results of precision measurements of 1 MΩ quantum Hall resistance array made of the GaAsl AIGaAs heterosubstrate. Precision measurements have been performed with a cryogenic current comparator resistance bridge by comparing the array resistance to a 10 kΩ resistance standard traceable to the quantum Hall effect. Stability of the quantization in the array within the relative standard uncertainty of 18 ×10
^-9
through repeated thermal cycles reflects the invariant quantum nature of the array resistance in a given condition.