Optical investigation of electrical spin injection into semiconductors

Abstract

We investigate the electrical injection of spin-polarized electrons into a semiconductor ͓Al͑GaAs͔͒ heterostructure from ferromagnetic FeCo metal through an AlO x tunnel barrier. We have developed the optical oblique Hanle effect approach for the quantitative analysis of electrical spin injection into semiconductors. This technique is based on the manipulation of the electron spins within a semiconductor when spin polarized electrons have been injected. This allows us to clearly separate the effects caused by spin injection from others, that are magneto-optical, Zeeman, etc. Simultaneously, the oblique Hanle effect approach provides additional information on the spin dynamics in the semiconductor. In the FeCo/AlO x /Al(GaAs) heterostructures we observe spin injection of 21% and 16% at 80 and 300 K, respectively. The importance of electron thermalization effects and the impact of the doping level of the semiconductor for practical investigation of spin injection by optical means are demonstrated.

Spin filtering through ferromagneticBiMnO3tunnel barriers

“…Spin-polarized tunneling from a ferromagnetic metal through a nonmagnetic layer is also what can be used for spin injection into a semiconductor. 5 Another way for spin-polarized tunneling has been little explored: this is tunneling from a nonmagnetic electrode through a ferromagnetic insulator. The concept was reported by Moodera et al 6 with EuS tunnel barriers.…”

Double detected spin-dependent quantum dot

“…The emitted light is used for measuring the polarization of the injected spin or the spin dynamics in the quantum dot [32]. The photon detector in these experiments is the apparatus, which we modeled as the unsharp detector in the theory presented.…”

“…(32), that by measuring the electric current, the projections into different state correspond to different observed value of the current. This implies that the states of the quantum dot can be determined by monitoring directly the electric current.…”

Introduction to spin-polarized ballistic hot electron injection and detection in silicon

“…By fitting the data to the simulation, we can extract the transport variables v and D; along with the spin lifetime measurement, this comprises a spin Haynes-Shockley experiment. Equation (6.4) is valid only for the case of a purely perpendicular magnetic field B = B zẑ [102]. In the most general case, if there is also an in-plane field component B yŷ (owing to misalignment or a static field) and/or if the perpendicular component of the field B z is strong enough to overcome the in-plane magnetic anisotropy of the film, the cos ut term must be replaced with 5) where in the simplest case, the magnetization rotation angles q 1,2 = arcsin(tanh(B z /h 1,2 )), and h 1,2 are the demagnetization fields of injector and detector ferromagnetic layers (typically several tesla) [86].…”