Direct comparison of the quantized Hall resistance in gallium arsenide and silicon

Using an ultrasensitive, cryogenic, current-comparator bridge the quantized Hall resistance RH(2) in a GaAs/AlGaAs heterostructure has been compared directly with RH(4) in a silicon MOSFET. The measurements show that RH(2;GaAs)/RH(4;Si)=2[1-0.22(3.5)×{}10^-10]. Within the 1{σ} combined uncertainty of ±{}3.5×{}10^-10 the result suggests that the quantized Hall resistance is a universal quantity, independent of the host lattice and Landau-level index, and is probably equivalent to h/e², the relationship predicted theoretically.