Because silicon is one of the most intensively studied materials, on which the modern technology has been founded, one might think that no phenomenon remains to be discovered in it. Nevertheless, we found a new property of silicon; in a high electric field silicon shows large positive magnetoresistance between 0 T and 3 T more than 1,000 % at room temperature and 10,000 % at 25 K. The experiment on the lightly doped silicon reveals that when the carrier density decreases below 1013/cm3, the magnetoresistance in high electric fields exhibits linear dependence on the field between 3 T and 9 T. We propose that the quasi-neutrality breaking in the space charge effect in the high electric field induces inhomogeneity in silicon, yielding the unusual non-saturating magnetoresistance as in the inhomogeneous semiconductors. While large positive magnetoresistance at room temperature was achieved in the metal-semiconductor hybrid devices, it is now realized in a simpler structure in a way different from other known magnetoresistive effects. This novel effect can be utilized to develop new magnetic devices from silicon, which is expected to advance the current silicon technology. [fig1]
[1] M. P. Delmo, S. Yamamoto, S. Kasai, T. Ono, and K. Kobayashi, Large positive magnetoresistive effect in silicon induced by the space-charge effect, Nature 457, 1112 (2009).
[2] Michael P. Delmo, Shinya Kasai, Kensuke Kobayashi, Teruo Ono, Current-controlled magnetoresistance in silicon in non-Ohmic transport regimes Appl. Phys. Lett. 95, 132106 (2009).

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