Large magnetoresistance in Si:B-SiO2-Al structures

A magnetic-field-dependent resistance change of eight orders of magnitude is observed in boron-doped Si-SiO(2)-Al structures. In order to identify the elementary mechanisms governing this phenomenon, the thickness of the oxidic layer, which is used as an interface energy barrier, has been varied by changing the exposure time to an oxygen plasma. Next, the chemical composition has been monitored by in situ x-ray photoelectron spectroscopy measurements. From current-voltage measurements, we observe that at low temperatures, an ultrathin SiO(2) layer provides the kinetic energy to trigger an autocatalytic process of impact ionization. A magnetic field suppresses the onset of impact ionization to higher electric fields, resulting in a large magnetoresistance. (C) 2008 American Institute of Physics.