Magnetoresistive switch effect in metal/semiconductor hybrid granular films: extremely huge magnetoresistance effect at room temperature

Hybrid granular films, consisting of nanoscale metal clusters that are grown on a GaAs substrate by molecular beam epitaxy, exhibit magnetic-field-sensitive current-voltage (I-V) characteristics at room temperature. When a constant voltage, above the threshold value, is applied to the film. the I-V curve becomes nonlinear and a breeding-like current increase appears. The abrupt increase disappears with the application of magnetic fields, which we call the magnetoresistive switch. The switch yields the huge positive magnetoresistance effect, for example 320 000% at 2 kOe. The origin of the magnetoresistive switch effect is discussed in terms of a magnetic-field dependence of an avalanche breakdown.