The Optically Induced and Bias-Voltage-Driven Magnetoresistive Effect in a Silicon-Based Device

The giant change in photoconductivity of a device based on the Fe/SiO2/p-Si structure in magnetic field is reported. As the magnetic field increases to 1 T, the conductivity changes by a factor of more than 25. The optically induced magnetoresistance effect is strongly dependent of the applied magnetic field polarity, as well as of sign and value of a bias voltage across the device. The main mechanism of the magnetic field effect is related to the Lorentz force, which deflects the trajectories of photogenerated carriers, thereby changing their recombination rate. The structural asymmetry of the device leads to the asymmetry of the dependence of recombination on the magnetic field polarity: recombination of carriers deflected in the bulk of semiconductor is relatively slow, while recombination of carriers at the SiO2/p-Si interface is faster. In the latter case, the interface states serve as effective recombination centers. The bias voltage sign specifies the type of carriers, whose trajectories pass near the interface, providing the main contribution to the magnetoresistance effect. The bias voltage controls the electric field accelerating carriers and, thus, affects the hole and electron trajectories. Moreover, when the bias voltage exceeds a certain threshold value, the electron impact ionization regime is implemented. The magnetic field suppresses impact ionization by enhancing recombination, which makes the largest contribution to the magnetoresistance of the device. The investigated device can be used as a prototype of silicon chips controlled simultaneously by optical radiation, magnetic field, and bias voltage.