Tunnelling current in semimagnetic semiconductor heterostructures

We have investigated theoretically the spin-polarised tunnelling current th rough a triple-barrier structure based on semimagnetic semiconductors. In t his device the resonant tunnelling for each spin state is achieved at diffe rent bias, yielding well defined peaks in the I-V curve that have high degr ee of spin polarisation. Spin-flip scattering gives rise to additional peak s in the I-V curve when the alignments of the levels with opposite spins oc cur. We have used perturbation theory to treat the spin-dependent scatterin g mechanism, which in our model is driven by the thermal fluctuation of the ion magnetic moments. A double-barrier-tunnelling device has also been inv estigated, in which we found current with high degree of spin polarisation, even when the aforementioned spin-flip mechanism is considered. This devic e has potential applications as a spin filter. (C) 2000 Elsevier Science B. V. All rights reserved.