  The magneto-electric properties of resonant tunneling double barrier
structures using GaMnAs for the quantum well is investigated within a
self-consistent Green's function approach and a tight-binding electronic
structure model. The magnetic state of the well is determined self-consistently
by the tunneling current which controls the hole spin density and, hence, the
degree of exchange splitting of the subbands inside the well. Prompted by
recent experiments we compare model systems of increasing defect concentration
(substitutional disorder) regarding their I-V curve, magnetic state, and spin
polarization. We predict that, near resonance, the ferromagnetic order which
may be present at zero bias in the GaMnAs well tends to be destroyed. Resonance
peaks are found to be more sensitive to disorder than ferromagnetic ordering
and spin polarization of the steady-state current.
