Tunnelling current in semimagnetic semiconductor heterostructures

Abstract

We have investigated theoretically the spin-polarised tunnelling current through a triple-barrier structure based on semimagnetic semiconductors. In this device the resonant tunnelling for each spin state is achieved at different bias, yielding well defined peaks in the I– V curve that have high degree of spin polarisation. Spin-flip scattering gives rise to additional peaks in the I– V curve when the alignments of the levels with opposite spins occur. We have used perturbation theory to treat the spin-dependent scattering mechanism, which in our model is driven by the thermal fluctuation of the ion magnetic moments. A double-barrier-tunnelling device has also been investigated, in which we found current with high degree of spin polarisation, even when the aforementioned spin-flip mechanism is considered. This device has potential applications as a spin filter.