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

Using an ultrasensitive, cryogenic, current-comparator bridge the quantized Hall resistance ${\mathit{R}}_{\mathit{H}}$(2) in a GaAs/AlGaAs heterostructure has been compared directly with ${\mathit{R}}_{\mathit{H}}$(4) in a silicon MOSFET. The measurements show that ${\mathit{R}}_{\mathit{H}}$(2;GaAs)/${\mathit{R}}_{\mathit{H}}$(4;Si)=2[1-0.22(3.5)×${10}^{\mathrm{-}10}$]. Within the 1σ combined uncertainty of ±3.5×${10}^{\mathrm{-}10}$ 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/${\mathit{e}}^2$, the relationship predicted theoretically.