Enhanced carrier lifetimes and suppression of midgap states in GaAs at a magnetic metal interface

We report the first measurement of room temperature carrier lifetimes at a magnetic metal-semiconductor interface, Fe/GaAs(001)-(2 x 4). The lifetimes are significantly enhanced relative to uncoated or sulfur-passivated surfaces. or the Al/GaAs(001)-(2 x 4) interface. These enhanced life-times correlate with a corresponding decrease in the density of midgap states which otherwise dominate the character of the GaAs(001) surface, The epitaxial Fe film provides both a ferromagnetic contact and a superior surface-passivating layer which does not pin the Fermi energy.