Abstract
The high efficiency of a magnetic tunnel transistor as a source of spin-polarized electrons has been proven recently [X. Jiang et al., Phys. Rev. Lett. $90,$ 256603 (2003)]. A concept of this device based on an active group of hot electrons controlling the collector current and experiencing predominantly inelastic scattering in the base is developed. It takes into account the connection between the injection and filtering of spin-polarized electrons inside the device. Explicit expressions for the parameters of the device in terms of the basic parameters of the system are presented.
Highlights
Despite spectacular progress achieved during the last couple of years, efficient spin injection from ferromagneticFMmetallic emitters still remains one of the central problems of semiconductor spintronics.[1]
In what follows I propose an analytical theory of such spintronic devices. This theory of three-terminal devicessuch as MTT, based on a different physical concept, in its formalism generalizes the theory of two-terminal diffusive[14,15,16,17] and ballistic[18] devices and, establishes a connection to them. It is an important property of the MTT source that it employs both spin injection and spin filtering and, in this way, increases spin polarization of the electron beam
Are the barrier transparencies for the right- and left-moving electrons, respectively, near the energy stands for the current of those left-moving electrons at the left boundary of the base that were reflected elastically from the Schottky barrier and did not experience inelastic scattering in the base; they have enough energy to return to the emitter
Summary
The current is carried mostly by the electrons in close vicinity of the distribution function can be written as f ␣(x,vx)ϭ f 0(E) ϩ(d f 0 /dE)␣(x,vx), where ␣ϭ(↑,↓) is the spin index and. Milne equation and solved when the spin-diffusion length Le is large as compared with the electron mean free path.[18] For this purpose it is convenient to change from the functions. ␣(x,vx) to functions e␣(x,vx)ϭϪ␣(x,vx)ϩe(x)͔, where (x) is the electrostatic potential and Ϫe(eϾ0) is the electron charge. Far from the tunnel junction, in the diffusion region, the functions ␣(x,vx) averaged over v acquire the meaning of electrochemical potentials ␣(x). A solution of the Boltzmann problem depends on the boundary values. The spin-injection coefficient at the contact boundary, ␥eϭ( j↑. Le is a spindiffusion length, and are conductivities of spin-up and spin-down electrons.[23]
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