Fabrication and characterization of quantum Hall devices for the resistance standard at CMS

We fabricated AlGaAs/GaAs heterostructure-based quantum Hall devices for the resistance standard at Center for Measurement Standards (CMS). The measurements using a Direct Current Comparator (DCC) show the consistency between the plateaus of v=2 and 4 at the temperature T=2 K, where v is the filling factor. On the other hand, the plateaus of higher filling factors may be susceptible to the reduced localization strength, under which the semiclassical effects can be important. The coexistence of localization-induced gaps and semiclassical transport is discussed.