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Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 35: Symposium Ferromagnetische Halbleiter

HL 35.7: Talk

Thursday, March 11, 2004, 13:15–13:45, H15

GaN-based semiconductor compounds for spin electronics — •Bernd Beschoten — 2. Physikalisches Institut, RWTH Aachen, Templergraben 55, 52056 Aachen

According to recent predictions of room temperature ferromagnetism in Mn-doped GaN, the material might be promising for spintronic applications. In the first part, the talk will focus on the material science aspects and magnetic properties of Mn-doped GaN layers grown by molecular beam epitaxy. Samples with low Mn content are homogeneous alloys showing spin-glass like behavior at low temperatures, but they are NOT ferromagnetic. Samples with higher Mn content additionally exhibit ferromagnetism with Curie temperatures of about 750 K, which originates from nm-scale Mn-rich clusters formed during growth.

The second part of the talk is devoted to the study of spin coherence and spin dephasing in n-type GaN, which is another important aspect for GaN-based spintronics. Despite densities of charged threading dislocations of 5 × 108 cm−2, this coherence studied by time-resolved Faraday rotation yielding lifetimes of ∼ 20 ns at T = 5 K, and persists to room temperature. The doping dependence of spin dephasing is compared to n-GaAs, suggesting a common origin for spin relaxation in these systems.

Work done in collaboration with D.D. Awschalom, O. Brandt, L. Däweritz, S. Dhar, A. Dohmen, K.J. Friedland, G. Güntherodt, E. Hu, E. Johnston-Halperin, J. Keller, K.H. Ploog, and A. Trampert. Supported by the German Federal Ministry of Education and Research (BMBF).

[1] S. Dhar et al., Appl. Phys. Lett. 82, 2077 (2003).

[2] B. Beschoten et al., Phys. Rev. B 63, 121202 (2001).

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