Magnetic field dependence of 2D sodium impurity band conduction in activated regions

We have measured the temperature dependence of conductance of electrons in 2D sodium induced impurity bands in silicon inversion layers from 4.2 to 80 K observing both activation of electrons to a mobility edge. E1, and nearest neighbor hopping, E3 in magnetic fields up to 25 T. The results are that E1 decreases slightly between 0 and about 20 T and then increases slightly. The prefactor decreases by about a factor of four. E3 increases monotonically. None of these results was expected. © 1984.