Abstract:

Efficient injection of spin-polarized electrons from a ferromagnetic (FM) source into a semiconducting heterostructure is a prerequisite for the realization of semiconductor spintronic devices. However, due to the large conductivity mismatch between FM metals and semiconductors, direct deposition of the FM metal on the semiconductor surface will result in very poor spin injection efficiency [1]. In this talk, I will introduce two methods to overcome this impedance obstacle to get high spin-injection efficiency. (1) By insertion of a thin MgO tunnel barrier between FM and GaAs, we have obtained 32% circular polarization for spin-injection in GaAs.[2] (2) By using hot electron injection and detection technique, we have obtained 50% spin injection in Si.[3,4]
[1] A. Fert and H. Jaffr¨¨s, Phys. Rev. B 64, 184420 (2001).
[2] Y. Lu, V. G. Truong, P. Renucci, M. Tran, H. Jaffr¨¨s, C. Deranlot, J.-M.George, A. Lema?tre, Y. Zheng, D. Demaille, P.-H. Binh, T. Amand, and X. Marie, Appl. Phys. Lett. 63, 054416 (2008).
[3] Y. Lu and I. Appelbaum, Appl. Phys. Lett. 97, 162501 (2010).
[4] Y. Lu, J. Li and I. Appelbaum, Phys. Rev. Lett. 106, 217202 (2011).
 
 
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