Extremely large magnetoresistance in silicon

CT 5: Monday, 14:30 - 14:45 Silicon holds exceptional promise for magnetoelectronics, by virtue of its long spin coherence and compatibility with the current CMOS technology. As a possible implicit contribution for future silicon based spintronics devices, weshow for the first time, using non magnetic materials, a robust low temperature positive resistance change up to eight orders of magnitude at a magnetic field of 500 mT in lateral boron-doped Si/SiO2/Al devices [1]. Systematic investigation of the role of the thin silicondioxide layer shows that the charge acceleration across the barrier provides the energy to trigger an autocatalytic process of impact ionization. A small magnetic field causes shrinkage of the acceptor wave functions and the overlap by the tails is reduced. Thereby, the acceptor energy level increases with respect to the valence band, as verified by admittance spectroscopy, by which the activation energy for impact ionization significantly increases, strongly suppressing the current. A macroscopic transport model is introduced that is able to describe how the magnetoresistance is controlled by voltage, direction of the magnetic field, electrode spacing and oxide thickness. By choosing deeper acceptor states, these huge magnetoresistance effects might be scaled up to higher temperature, where the device could be suitable as a magnetoresistive sensor or to construct spin logic. [1] J.J.H.M. Schoonus, H.J.M. Swagten, B. Koopmans et al., Phys. Rev. Lett. 100 (2008) 127202.