| AVS 55th International Symposium & Exhibition | |
| Magnetic Interfaces and Nanostructures | Wednesday Sessions |
| Session MI-WeA |
| Session: | New Directions in Spintronics |
| Presenter: | G. Kioseoglou, Naval Research Laboratory |
| Authors: | G. Kioseoglou, Naval Research Laboratory A.T. Hanbicki, Naval Research Laboratory C.H. Li, Naval Research Laboratory P.E. Thompson, Naval Research Laboratory O.M.J. van 't Erve, Naval Research Laboratory M. Holub, Naval Research Laboratory C. Awo-Affouda, Naval Research Laboratory R. Goswami, Naval Research Laboratory G. Spanos, Naval Research Laboratory B.T. Jonker, Naval Research Laboratory |
| Correspondent: | Click to Email |
Electrical spin injection is a prerequisite for a semiconductor spintronics technology. While significant progress has been realized in GaAs, little has been made in Si, despite its overwhelming dominance of the semiconductor industry. Si is an ideal host for spin-based functionality due to its smaller spin orbit than GaAs (responsible for spin relaxation) and to its long spin lifetimes (microseconds). Recently1 we have reported successful injection of spin-polarized electrons from an Fe film through an Al2 O3 tunnel barrier into Si (001). The circular polarization of the electroluminescence (EL) resulting from radiative recombination in Si and in GaAs (in Si/AlGaAs/GaAs structures) tracks the Fe magnetization, confirming that these spin polarized electrons originate from the Fe contact. The polarization reflects Fe majority spin. We determined a lower bound for the Si electron spin polarization of ~30% at 5K, with significant polarization extending to at least 125K. Here we compare electrical spin injection from Fe into MBE grown Si n-i-p heterostructures using different tunnel barriers- a reversed biased Fe/Si Schottky contact and an Fe/Al2 O3 barrier. For both types of structures the EL spectra are dominated by transverse acoustic and optical phonon emissions in the Si and the circular polarization of the EL due to radiative recombination in the Si tracks the Fe out of plane magnetization. However, the polarization is almost 50% lower for the Fe/Si contact than that of the Fe/Al2 O3/Si system. This could be due to different interface structure or it may result from changes in the transport mechanism involved. Systematic TEM analysis has been performed to correlate the interface structure with the observed optical polarization, and reveals some Fe/Si intermixing that is absent in the Fe/ Al2 O3/Si structure. While the zero bias resistance for the Fe/ Al2 O3/Si system shows very weak temperature dependence, the resistance for the Fe/Si system increases orders of magnitude with decreasing temperature. This implies that two different transport mechanisms may be responsible for the spin injection.
1B.T. Jonker, G. Kioseoglou, A.T. Hanbicki, C.H. Li, and P.E. Thompson, Nature Physics 3, 542 (2007). This work was supported by ONR and core programs at NRL.