Ballistic spin filtering across the ferromagnetic-semiconductor interface

Li Li

doi:10.5488/cmp.15.13701

Abstract

The ballistic spin-filter effect from a ferromagnetic metal into a semiconductor has theoretically been studied with an intention of detecting the spin polarizability of density of states in FM layer at a higher energy level. The physical model for the ballistic spin filtering across the interface between ferromagnetic metals and semiconductor superlattice is developed by exciting the spin polarized electrons into n-type AlAs/GaAs superlattice layer at a much higher energy level and then ballistically tunneling through the barrier into the ferromagnetic film. Since both the helicity-modulated and static photocurrent responses are experimentally measurable quantities, the physical quantity of interest, the relative asymmetry of spin-polarized tunneling conductance, could be extracted experimentally in a more straightforward way, as compared with previous models. The present physical model serves guidance for studying spin detection with advanced performance in the future.

Highlights

Based on spin-polarized electrons as information carrier, spintronics has been developing as an attractive field for a new generation of electronic devices, in which the injection and detection of spinpolarized carriers has been recognized as a significant challenge [1, 2]
The spin injection efficiency from FM to SC could be directly measured by using a built-in light emission diode (LED) structure and detecting its circular polarization degree of electric photoluminescence (e-PL) [4,5,6]
The asymmetry in the absorption for the σ+ and σ− lights could be induced by magnetic circular dichroism (MCD) inside the FM layer itself [9, 16]

Summary

Introduction

Based on spin-polarized electrons as information carrier, spintronics has been developing as an attractive field for a new generation of electronic devices, in which the injection and detection of spinpolarized carriers has been recognized as a significant challenge [1, 2]. The spin injection efficiency from FM to SC could be directly measured by using a built-in light emission diode (LED) structure and detecting its circular polarization degree of electric photoluminescence (e-PL) [4,5,6]. The measured spin-dependence of tunneling current relates to many other facts except for the intrinsic effect, for example, the photon energy of the exciting light [10,11,12,13] and the characteristic temperature [14, 15]. The asymmetry in the absorption for the σ+ and σ− lights could be induced by magnetic circular dichroism (MCD) inside the FM layer itself [9, 16]

Current theory

Present principle and method

Theoretical model

Conclusions