Metal-nanocluster equipped GaAs surfaces designed for high-sensitive magnetic field sensors

A huge positive magnetoresistance (MR) effect, more than 105% at room temperature (RT), has been discovered in metal-nanocluster equipped GaAs surfaces. Granular film consisting of nanoscale MnSb metal-clusters that are grown on a sulfur-terminated GaAs(0 0 1) substrate by molecular-beam epitaxy exhibits magnetic-field-sensitive current–voltage characteristics. When a constant voltage, above the threshold value, is applied to the film, very steep change in the current, which we term magnetoresistive switch, is driven by the huge MR effect under a relatively low magnetic field at RT. The origin of the magnetoresistive switch effect is discussed in terms of a novel concept of magnetic-field-sensitive avalanche breakdown. These properties strongly depend on the morphological condition of metal-nanoclusters, and seem to depend on electronic properties of the GaAs surface.