Probing the plateau-insulator quantum phase transition in the quantum Hallregime

We report quantum Hall experiments on the plateau-insulator transition in a low mobility In0.53Ga0.47As/InP heterostructure. The data for the longitud inal resistance rho(xx) follow an exponential law and we extract a critical exponent kappa = 0.55 +/- 0.05 which is slightly different from the establ ished value kappa = 0.42 +/- 0.04 for the plateau transitions. Upon correct ion for inhomogeneity effects, which cause the critical conductance sigma(x x)* to depend marginally on temperature, our data indicate that the plateau -plateau and plateau-insulator transitions are in the same universality cla ss.