Unification of the metal-insulator transitions driven by the impurity concentration and by the magnetic field in arsenic-doped germanium

We show that one can unify the scaling behavior of the conductivity in Ge:As in the vicinity of the metal-insulator transition driven either by the concentration of impurities N or by the magnetic field B by introducing a new scaling variable U=[(N/Nc)-(B/B*)-1], where both the critical impurity concentration Nc and the characteristic magnetic field B* are constant.