ABSTRACT
Spin-dependent electron tunneling in III-V semiconductors has become the subject of intensive study in the search for an effective non-magnetic spin injector. Non-magnetic spin filters are appealing since they do not require a magnetic field and they allow spin manipulation to be achieved with applied voltage. It is known that the direct contact between a ferromagnetic metal and a semiconductor has low spin injection efficiency due to the conductivity mismatch [1]. To improve the efficiency of spin transfer between a metal and a semiconductor, electrical contacts of increased resistance are proposed in Ref. [2]. The possible implementation of this approach is tunnel contact between nonmagnetic semiconductors with intrinsic spin splitting. Spin selection in tunnel contacts occurs in the course of electron transmission through a single-or double-barrier-quantum well (QW) if the spin-orbit interaction is essential. The study of tunnel spin discrimination started with cubic [100]-oriented InGaAs-based heterostructures. The case of wurtzite AlGaN quantum wells is more complex as symmetry allows intrinsic linear k-dependent spin splitting to exist. The polarization fields distort the band structure making the extrinsic Rashba term nonzero as the structure becomes electrically asymmetric. One more difference between cubic and wurtzite structures is that the Dresselhaus and Rashba terms in
wurtzite structures have the same momentum-dependent spin symmetry (see Chapter 2).
