Scaling and Universality of Integer Quantum Hall Plateau-to-Plateau Transitions

We have investigated the integer quantum Hall plateau-to-plateau transition in two-dimensional electrons confined to ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}\mathrm{\text{−}}{\mathrm{Al}}_{0.33}{\mathrm{Ga}}_{0.67}\mathrm{As}$ heterostructures over a broad range of Al concentration $x$. For $x$ between 0.65% and 1.6%, where the dominant contribution to disorder is from the short-range alloy potential fluctuations, we observe a perfect power-law scaling in the temperature range from 30 mK to 1 K with a critical exponent $\kappa =0.42\pm 0.01$.