Spin Injection Across a Heterojunction: A Ballistic Picture

Abstract

Spin injection across heterojunctions plays a decisive role in the new field of spintronics. Within the ballistic transport regime, we state a general expression for the spin-injection rate in a heterojunction made of two ballistic electrodes. Both the spin-orbit interaction and interface scattering effect are taken into account. Our model is consistent with the well-documented results of ferromagnetic-metal junctions. It explains the recent experimental results of a dilute-magnetic-semiconductor/semiconductor junction and predicts solutions to enhance the spin-injection rate across a ferromagnetic-semiconductor junction.

Spin injection across a hybrid heterojunction: Theoretical understanding and experimental approach (invited)

“…Benefiting from such a spindependent scattering nature, we found can be further enhanced by inserting a thin tunneling barrier at the interface. 18 This is consistent with the result of an earlier diffusive model proposed by Rashba. 14 To demonstrate the advantage of the semiconductor in a hybrid device, we extended our theory 21 to calculate the change of magnetoconductance on carrier density for a realistic hybrid device, depicted in Fig.…”

“…This value is of the same order as that calculated in our theory for spin injection. 18 On devices with larger 2DEG channel lengths L, dips instead of peaks are observed. We found a systematic channel length dependence of the normalized resistance change 12 that demonstrates the importance of transport in the 2DEG channel.…”

Spintronics: Fundamentals and applications

“…Blonder et al (1982) used a similar approach, known as the Blonder-Tinkham-Klapwijk method, in which the two limits correspond to Z→0 and Z→ϱ, respectively, and Z is the strength of the ␦-function barrier. The transparency of this approach 98 makes it suitable for the study of ballistic spin-polarized transport and spin injection even in the absence of a superconducting region (Heersche et al, 2001;Hu and Matsuyama, 2001;Hu, Nitta, et al, 2001;Matsuyama et al, 2002). It is instructive to note a similarity between the twocomponent transport in N/S junctions (for electronlike and holelike quasiparticles) and F/N junctions (for spin ↑, ↓), which both lead to current conversion, accompanied by additional boundary resistance (Blonder et al, 1982;van Son et al, 1987).…”

“…IV.A.3. Considering spin-orbit coupling and the potential scattering at the F/N interface modeled by the ␦ function, Hu and Matsuyama (2001) have examined ballistic spin injection in the F/N junction. They show that even a spin-independent barrier can be used to enhance the spin injection and lead to an increase in the conductance polarization.…”

Rashba effect and magnetic field in semiconductor quantum wires

“…7,8,9,10 This is the basis of the spin dependent field-effect-transistor (spinFET) earlier discussed theoretically by Datta and Das. 11 Numerous theoretical spintronic devices have been proposed using interference, 12,13,14,15 resonant tunneling, 16,17,18,19 ferromagnet-semiconductor hybrid structures, 20,21,22,23 multiterminal geometries, 24,25,26,27 and adiabatic pumping. 28 Magnetic field effects on the transport properties in 2D systems with SOI have been investigated theoretically 29,30,31 as well as experimentally 7,8,9,10,32,33 .…”