title: Enhancement of the spin accumulation at the interface between a spin-polarized tunnel junction and a semiconductor.
abstract: We report on spin injection experiments at a Co/Al2O3/GaAs interface with electrical detection. The application of a transverse magnetic field induces a large voltage drop DeltaV at the interface as high as 1.2 mV for a current density of 0.34 nA.microm(-2). This represents a dramatic increase of the spin accumulation signal, well above the theoretical predictions for spin injection through a ferromagnet/semiconductor interface. Such an enhancement is consistent with a sequential tunneling process via localized states located in the vicinity of the Al2O3/GaAs interface. For spin-polarized carriers these states act as an accumulation layer where the spin lifetime is large. A model taking into account the spin lifetime and the escape tunneling time for carriers traveling back into the ferromagnetic contact reproduces accurately the experimental results.
authors.affiliation: Unité Mixte de Physique CNRS-Thales, Route départementale 128, 91767 Palaiseau Cedex and Université Paris-Sud 91405, Orsay, France. michael.tran@thalesgroup.com
authors.forename: M
authors.initials: M
authors.lastname: Tran
authors.forename: H
authors.initials: H
authors.lastname: Jaffrès
authors.forename: C
authors.initials: C
authors.lastname: Deranlot
authors.forename: J-M
authors.initials: JM
authors.lastname: George
authors.forename: A
authors.initials: A
authors.lastname: Fert
authors.forename: A
authors.initials: A
authors.lastname: Miard
authors.forename: A
authors.initials: A
authors.lastname: Lemaître