Quantum Hall Effect as an Electrical Resistance Standard

A special modulation doped Al0.3Ga0.7As/GaAs sample was used in this manuscript with a main objective to demonstrate the application of the integer quantum Hall effect as an universal standard for electrical resistance measurements. The n-type impurities are introduced at a distance of 20 nm from the hetero interface. Some of the electrons are captured in the potential well, far from the impurity atoms. Extremely high carrier mobility (m(eff) = 480000 cm(2)/Vs at T = 4.2 K) is obtained due to this separation through a significant reduction in ionized impurity scattering.