Transition from 1-dimensional to 2-dimensional hopping conductivity in silicon accumulation layers

We have used p+ diffusions to confine electrons in an accumulation layer on n- silicon. This allowed for electrical control of the channel width. When the channel was narrowest the conductance followed lnσ = -(To/T) 1 2; when it was wider it followed lnσ = -(To'/T) 1 3. These results are consistent with a transition from 1D to 2D variable range hopping. Strong structure in the conductance as a function of carrier concentration occurred which may be the result of fluctuations in the density of states in the band tail. In the 1D range, the effect of high magnetic field is to increase the power law; in the 2D range, magneto-oscillations were observed above 7T. © 1983.