Efficient nonlinear room-temperature spin injection from ferromagnets into semiconductors through a modified Schottky barrier

We show that spin polarization of electrons in nonmagnetic semiconductors near specially tailored ferromagnet-semiconductor junctions can achieve 100%. This effect is realized even at moderate spin injection coefficients of the contact when these coefficients only weakly depend on the current. The effect of complete spin extraction occurs at relatively strong electric fields and arises from a reduction of spin penetration length due to the drift of electrons from a semiconduc...

We report electrical spin injection from a ferromagnetic metal contact into a semiconductor light emitting diode structure with an injection efficiency of 30% which persists to room temperature. The Schottky barrier formed at the Fe/AlGaAs interface provides a natural tunnel barrier for injection of spin polarized electrons under reverse bias. These carriers radiatively recombine, emitting circularly polarized light, and the quantum selection rules relating the optical and ca...

Efficient injection of spin-polarized electrons into the conduction band of silicon is limited by the formation of a silicide at the ferromagnetic metal (FM)/silicon interface. In the present work, this "magnetically-dead" silicide (where strong spin-scattering significantly reduces injected spin polarization) is eliminated by moving the FM in the spin injector from the tunnel junction base anode to the emitter cathode and away from the silicon surface. This results in over a...

The electrical creation and detection of spin accumulation in ferromagnet/semiconductor Schottky contacts that exhibit highly non-linear and rectifying electrical transport is evaluated. If the spin accumulation in the semiconductor is small, the expression for the spin voltage is identical to that of linear transport. However, if the spin accumulation is comparable to the characteristic energy scale that governs the degree of non-linearity, the spin detection sensitivity and...

A quantum theory of the spin-dependent scattering of semiconductor electrons by a Schottky barrier at an interface with a ferromagnet is presented. The reflection of unpolarized non-equilibrium carriers produces spontaneous spin-polarization in the semiconductor. If a net spin-polarization pre-exists in the semiconductor, the combination of the ferromagnet magnetization and the incident carrier polarization combine to tilt the reflected polarization in the semiconductor. The ...

New mechanism of magnetoresistance, based on tunneling-emission of spin polarized electrons from ferromagnets (FM) into semiconductors (S) and precession of electron spin in the semiconductor layer under external magnetic field, is described. The FM-S-FM structure is considered, which includes very thin heavily doped (delta-doped) layers at FM-S interfaces. At certain parameters the structure is highly sensitive at room-temperature to variations of the field with frequencies ...

We predict it is possible to achieve high-efficiency room-temperature spin injection from a mag- netic metal into InAs-based semiconductors using an engineered Schottky barrier based on an InAs/AlSb superlattice. The Schottky barrier with most metals is negative for InAs and positive for AlSb. For such metals there exist InAs/AlSb superlattices with a conduction band edge perfectly aligned with the metal's Fermi energy. The initial AlSb layer can be grown to the thickness req...

In order to enhance spin injection efficiency from ferromagnetic (FM) metal into a two-dimensional electron gas (2DEG), we introduce another FM metal and two tunnel barriers (I) between them to investigate the current polarization in such ballistic FM/I/FM/I/2DEG junction. Our treatment is based on the free-electron scattering theory. It is found that due to quantum interference effect, the magnitude and sign of the current polarization exhibits periodical oscillating behavio...

Current understanding of spin injection tells us that a metal ferromagnet can inject spin into a semiconductor with 100% efficiency if either the ferromagnet is an ideal half metal with 100% spin polarization, or there exists a suitable tunnel barrier at the interface. In this paper, we show that, at absolute zero temperature, 100% spin injection efficiency from a non-ideal metal ferromagnet into a semiconductor quantum wire can be reached at certain injection energies, witho...

We propose a spin-dependent resonant tunneling structure to efficiently inject spin-polarized current into silicon (Si). By means of a heavily doped polycrystalline Si (Poly-Si) between the ferromagnetic metal (FM) and Si to reduce the Schottky barrier resistance, we estimated raising the tunneling current density up to $10^8$Am$^{-2}$. The small Fermi sea of the charge carriers in Si focuses the tunneling electrons to the resonant spin states within a small region of transve...