Crossover phenomenon for variable range hopping conduction in strong magnetic field

Crossover from Mott to Efros-Shklovskii (ES) Variable Range Hopping (VRH) conduction has been observed upon lowering temperature in barely insulating n-GaAs. We show that all the resistivity data, for different magnetic fields, obey a universal scaling function the two asymptotic forms of which are Mott and ES VRH laws. The variations of the crossover temperature and of other pertinent parameters with increasing magnetic field are discussed.