  Semiconductor spintronics will need to control spin injection phenomena in
the non-linear regime. In order to study these effects we have performed spin
injection measurements from a dilute magnetic semiconductor [(Zn,Be,Mn)Se] into
nonmagnetic (Zn,Be)Se at elevated bias. When the applied voltage is increased
to a few mV we find a strong decrease of the spin injection efficiency. The
observed behavior is modelled by extending the charge-imbalance model for spin
injection to include band bending and charge accumulation at the interface of
the two compounds. We find that the observed effects can be attributed to
repopulation of the minority spin level in the magnetic semiconductor.
