Large tunneling magnetoresistance in GaMnAs/AlAs/GaMnAs ferromagnetic semiconductor tunnel junctions

We have observed very large tunneling magnetoresistance (TMR) in epitaxially grown Ga1-xMnxAs/AlAs/Ga1-xMnxAs ferromagnetic semiconductor tunnel junctions. Large TMR ratios more than 70% (maximum 75%) were obtained in junctions with a very thin (less than or equal to1.6 nm) AlAs tunnel barrier when the magnetic field was applied along the [100] axis in the film plane. The TMR was found to rapidly decrease with increasing barrier thickness, which is explained by calculations assuming that the parallel wave vector of carriers is conserved in tunneling.