Unravelling the mechanism of large room-temperature magnetoresistance in silicon

In this experimental study, we confirm that the magnetoresistance effect measured in boron-doped Si-SiO2-Al structures originates from bulk silicon, and prove that the magnetic field non-uniformly squeezes the acceptor wave functions. In line with the expectation that the effect of a magnetic field on an acceptor wave function becomes stronger with increasing distance from the impurity centre, we show that the magnetoresistance increases for decreasing doping concentration, although the role of background impurities in this process cannot be completely excluded. When using an ultrathin insulating layer instead of ohmic contacts in the latter devices, large constant-voltage magnetoresistances (MR > 1000% at 1 MA m-1) are obtained in low-doped silicon at room temperature.