  We investigate theoretically the efficiency of the Rashba effect, i.e. the
spin splitting resulting from an electric field. This is the mechanism behind
the Datta-Das spin transistor. In the research efforts so far the carriers have
usually been taken to be electrons. Here we demonstrate remarkable improvements
by several orders of magnitude by utilising holes instead. We also show that
the frequently neglected lattice-mismatch between GaAs and AlGaAs can be used
to further enhance the efficiency of the spin splitting mechanism. An inverse
Rashba effect is also demonstrated.
