Positive and Negative Magnetoresistance of a-C:Fe/Si Heterojunctions

The transition between positive and negative magnetoresistance (MR) is observed for Fe-doped amorphous carbon film/n-silicon (a-C:Fe/Si) heterojunctions. The sign of the MR changes as the applied bias voltage and temperature are changing. The MR transition voltage decreases from 0.2 to 0.06 V when temperature increases from 220 to 280 K. The transition from positive MR to negative MR is found to be accompanied by a decrease in slope of log(I) ~ log(V) plot. This phenomenon may be related to holes and electrons having different magnetic field responses.