Dresden 2003 – scientific programme

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MA: Magnetismus

MA 7: Spin-Elektronik

MA 7.9: Talk

Monday, March 24, 2003, 17:15–17:30, HSZ/401

Spin dephasing across the metal-insulator transition in n-GaAs — •T. Rohleder, M. Heidkamp, A. Oulmqadem, A. Tillmanns, B. Beschoten, and G. Güntherodt — II. Physikalisches Institut, RWTH Aachen, 52056 Aachen

Optically pumped electron spins in n-doped GaAs exhibit long spin lifetimes of more than 100 ns and spin coherence lengths longer than 100 µm [1]. The understanding and control of spin dephasing processes is crucial for spintronic devices. Using time-resolved Kerr spectroscopy we explore the relevant electronic states yielding these long spin lifetimes in Si doped bulk GaAs with donor concentrations ranging from 2×10¹⁵ cm⁻³ to 1×10¹⁸ cm⁻³. Depending on the photon energies both free band electron spins and donor spins can be excited and are distinguishable due to their different spin lifetimes and electron g-factors. We can assign the longest spin lifetimes of more than 100 ns to the donor-related electron spins, where we also find the strongest decrease in lifetime with increasing B-field. In contrast, free band electron states exhibit significantly shorter spin lifetimes of about 20 ns and a much weaker field dependence. Our results indicate the B-field dependent spin scattering mechanism for the donor-related spins to depend on the carrier localization length which diverges at the metal-insulator transition. Supported by BMBF FKZ 01BM160 and 13N8244.

[1] J.M. Kikkawa and D.D. Awschalom, Phys. Rev. Lett. 80 (19), 4313(1998), Nature 397, 139 (1999)