This chapter focuses on the electron spin degree of freedom in semiconductor spintronics. In particular, the electrostatic control of the spin degree of freedom is an advantageous technology over metal-based spintronics. Spin–orbit interaction (SOI), which gives rise to an effective magnetic field. The essence of SOI is that the moving electrons in an electric field feel an effective magnetic field even without any external magnetic field. Rashba spin–orbit interaction is important since the strength is controlled by the gate voltage on top of the semiconductor’s two-dimensional electron gas. By utilizing the effective magnetic field induced by the SOI, spin generation and manipulation are possible by electrostatic ways. The origin of spin-orbit interactions in semiconductors and the electrical generation and manipulation of spins by electrical means are discussed. Long spin coherence is achieved by special spin helix state where both strengths of Rashba and Dresselhaus SOI are equal.
Infinite Spin Diffusion Length of Any Spin Polarization Along Direction Perpendicular to Effective Magnetic Field from Dresselhaus and Rashba Spin–Orbit Couplings with Identical Strengths in (001) GaAs Quantum Wells