  We study spin precession due to Rashba spin splitting of electrons and holes
in semiconductor quantum wells. Based on a simple analytical expression that we
derive for the current modulation in a broad class of experimental situations
of ferromagnet/nonmagnetic semiconductor/ferromagnet hybrid structures, we
conclude that the Datta-Das spin transistor (i) is feasible with holes and (ii)
its functionality is not affected by integration over injection angles. The
current modulation shows a universal oscillation period, irrespective of the
different forms of the Rashba Hamiltonian for electrons and holes. The analytic
formulas approximate extremely well exact numerical calculations of a more
elaborate Kohn--Luttinger model.
