  We investigate the spin-dependent transport of GaMnAs-based magnetic tunnel
junctions (MTJs) containing a paramagnetic AlMnAs barrier with various
thicknesses. The barrier height of AlMnAs with respect to the Fermi level of
GaMnAs is estimated to be 110 meV. We observe tunneling magnetoresistance (TMR)
ratios up to 175% (at 2.6 K), which is higher than those of the GaMnAs-based
MTJs with other barrier materials in the same temperature region. These high
TMR ratios can be mainly attributed to the relatively high crystal quality of
AlMnAs and the suppression of the tunneling probability near at the in-plane
wave-vector k||=0.
