Giant injection magnetoresistance induced by femtosecond laser pulses in semiconductor / granular film heterostructures with cobalt nanoparticles

The light-induced giant injection magnetoresistance in SiO₂(Co)/GaAs heterostructures, where the SiO₂(Co) structure is the granular SiO₂ film with Co nanoparticles, has been studied. It is found that the photocurrent are accompanied by relaxation oscillations caused by the Coulomb influence and transitions between the photocurrent and electrons on the highest level in the interface quantum well. The light-induced magnetoresistance reaches its maximum value in the avalanche onset region and has the local minimum at the higher voltage. The local minimum is explained by delocalization of the highest level in the interface quantum well and by decrease of the probability of the backscattering process of injected electrons on deeper levels.