ABSTRACT
This chapter presents the theory of electrical spin injection through a hybrid metal–semiconductor interface. It is devoted to the mechanism of spin injection at the interface between a ferromagnetic (FM) conductor, and a semiconductor (SC). Efficient electrical spin injection from a ferromagnetic metal or a dilute magnetic semiconductor is the fundamental requirement of semiconductor-based spintronic devices. The efficiency of the electrical spin injection has been measured in hybrid FM/tunnel barrier/Sc devices, called spin-light-emitting diodes (LED), where the circular polarization of the electroluminescence probes the electron spin polarization degree in the semiconductor. The operation principle of a spin-LED is that the spin polarized electron in the FM metal will be injected electrically into the SC by applying a forward bias to the device. All the electroluminescence experiments cited up to now have been realized under a quasi-stationary electrical injection operating mode.
