Localization of nodal quasiparticles and plateau transitions

In the context of semiconductor physics, we propose a realization of 'unconventional' universality class in the problem of Anderson localization. In the beginning, we review our theoretical prediction on the critical phenomena driven by defects. It leads to 'critical metal' with continuously varying exponents in two dimensions. And we make some proposals for a realization of the critical metal in e.g. artificially designed semiconductor. Finally, we make some comments on the relation of this problem to the 'plateau transition' in e.g. GaAs/AlGaAs heterostructure