We have examined the electronic properties associated with semiconductor electrons that are in proximity with a ferromagnet. Instead of focusing on the injection of ferro-magnet electrons into the semiconductor through the interface, we have instead chosen to look at the properties of semiconductor electrons that can interact with a ferromagnetic epilayer. We have focused on two main effects: the reflection of non-equilibrium electrons from the interface, and the coupling of 2DEG with a ferromagnetic gate. Both have relevance to spintronics applications. For n-doped semiconductors with ferromagnetic epilayers, we have calculated the spin-dependent reflectivities for electrons incident on the Schottky barrier from the semi- conductor. We find that the shape of the barrier has a large impact on the asymmetry between reflection for the two spin channels, and significantly that the sign of the asymmetry can change depending on the system parameters. The ability to control the spin polarization by tuning the properties of the Schottky barrier (through the semiconductor doping or through an applied bias, for example) is very appealing for device design. We have further studied the effect of coupling 2DEG electrons at a semiconductor interface with a ferromagnetic gate separated from the semiconductor by a thin oxide barrier. Here, the electron is confined at the interface, which is similar to the multiple-reflection limit of the earlier work. We find that for very thin oxide barriers, the coupling of the 2DEG electrons to the ferromagnet is non-negligible. The self-energy of the 2DEG electrons due to the interaction with the ferromagnetic continuum produces both a spin-dependent level shift and a spin-dependent escape time. These spin effects can be exploited in transport-based devices. We find that the dominant effect is the broadening of the 2DEG energy levels due to the coupling. This effect opens a new scattering channel for 2DEG electrons to escape into the ferromagnetic continuum, which causes the in-plane conductivity of the 2DEG to become inherently spin dependent. We have described our recent proposal of a device which operates on this principle, consisting of a normal MOSFET-style device with the normal metallic gate replaced with two ferromagnetic gates that are very close together. Due to the spin dependence of the in-plane conductivity, a magnetoresistance effect occurs in the in-plane current depending on the relative orientation of the magnetizations of the two ferromagnetic gates. We have calculated the behavior of such a device for two realistic systems.
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