Complete spin polarization of electrons in semiconductor layers and quantum dots
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(a) Ferromagnet-semiconductor heterostructure containing a donor doped nonmagnetic semiconductor layer sandwiched between two FMs having opposite magnetizations, and , and two thin layers of a heavily doped degenerate S ( layers) between the and FM layers. (b) Energy diagrams of the heterostructure in equilibrium (broken curves) and at bias voltage (solid curves) in the case when the layers have a narrower band gap than that of the region, and the region is a degenerate S (for the nondegenerate region ). Here, is the Fermi level in equilibrium, is bottom of S conduction band, and are the values of in the and layers, respectively; and thicknesses of the and layers, respectively; and are the height and thickness of the Schottky barrier of the junctions. (c) Spatial dependence of electron spin polarization, , in the nondegenerate (solid lines) and degenerate S layer (dashed lines) for and at currents (curves 1), (curves 2), (curves 3), and (curves 4). Solid curves are calculated from Eq. (5) and dashed curves are obtained from numerical analysis of the diffusion-drift equation for .
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Schematic drawing of a ferromagnet S heterostructure (a). and are ferromagnetic layers with magnetization and (blue arrows); areas (1,3,4,5) are donor-doped S regions with different band-gap energy and placement of bottom of conduction band : , respectively; gray areas (2) are heavily doped degenerate S regions with ; dark gray area P is acceptor doped -semiconductor region. (b) Energy diagrams of the heterostructure in Sections I-I shown in Fig. 2(a). is the equilibrium Fermi level, and are quasi-Fermi levels for up- and down-electrons, respectively.
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