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We report on a theoretical study of giant magnetoresistance (GMR) effect in a δ -doped GaAs / Al x Ga 1 − x As heterostructure modulated by two stripes of ferromagnetic metal and a stripe of Schottky metal in parallel configuration. The δ -doping dependent transmission and conductance of the device are calculated. It is shown that a considerable giant magnetoresistance (GMR) effect exists in this structure. It is also shown that the magnetoresistance ratio ( MR ) can be switched by the δ -doping. The underlying physical mechanism of the results is analysed in light of δ -doping-dependent tunneling process in the device. [ABSTRACT FROM AUTHOR]

We report on a theoretical investigation of spin-polarized transport in a δ -doped magnetically modulated semiconductor nanostructure, which can be experimentally realized by depositing a ferromagnetic stripe on the top of a semiconductor heterostructure and by using the atomic layer doping technique such as molecular beam epitaxy (MBE). It is shown that although such a nanostructure has a zero average magnetic filed, a sizable spin polarization exists due to the Zeeman splitting mechanism. It is also shown that the degree of spin polarization varies sensitively with the weight and/or position of the δ -doping. Therefore, one can conveniently tailor the behaviour of the spin-polarized electron by tuning the δ -doping, and such a device can be employed as a controllable spin filter for spintronics. [ABSTRACT FROM AUTHOR]