采用转移矩阵法和Airy函数, 研究了ZnSe/ZnMnSe/ZnSe/ZnBeSe/ZnSe/ZnBeSe/ZnSe异质结构的自旋极化输运。在外加偏压和磁场对电子透射系数和自旋极化率的影响方面, 所得到的结论显现出复杂而有趣的特性。 磁场对自旋向上和向下电子隧穿的影响是不同的:对于自旋向上情况, 出现双共振向单共振转换现象。

Spintronics as a fast-developing interdisciplinary field, many novel devices, such as spin-FET and spin-LED, have been proposed. However, spin injection from ferromagnet to semiconductor has a low efficiency. In order to overcome this obstacle, diluted magnetic semiconductors (DMSs) have been proposed to realize the spin injection with high efficiency. In this paper, the spin-polarized tunnel through the ZnSe/ZnMnSe/ZnSe/ZnBeSe/ZnSe/ZnBeSe/ZnSe heterostructures is investigated by use of the transfer matrix and the linear combination of Airy functions. The bias and magnetic fields are both applied along the growth direction. The transmission coefficients as functions of the electron longitudinal energy are calculated, and some resonant peaks are observed. The transmission peaks for both spin-up and spin-down electrons move towards lower energy region with the increase of the applied voltage, which indicates that the bias can enhance the tunneling of electrons. For the spin-up case, the doublet resonance turn to singlet resonance with the increase of the magnetic field. However, the height of transmission peaks varies slightly with the magnetic field for the spin-down case. In our opinion, the reason that electrons with different spin have distinct transmission properties can be attributed to the fact that electrons are supposed by a spin-dependent potential in the DMS layer. Furthermore, we also calculate the spin polarization rate. It can be found that the spin polarization rate oscillates rapidly with the electron longitudinal energy in lower energy region, while converges to 0% in higher energy region. The curves of the rate shift towards lower energy region with the increase of the bias are as same as the transmission coefficient curves. Therefore, the spin-flip of electrons with specific energy can be realized by tuning the bias. External magnetic fields generally lift the spin polarization rate. It can be concluded that our heterostructure can be used as a spin-filter.