Recent Progress Towards the Development of Ferromagnetic Nitride Semiconductors for Spintronic Applications
This article describes progress towards producing prototype magnetoelectronic structures based on III-N semiconductor materials. We focus on the materials properties connected with the key physical phenomena underlying potential spintronic devices: producing, injecting, transporting, manipulating and detecting spin-polarized electron populations. Our experiments have shown that the maximum magnetic moment is realized for a composition of Ga0.97Cr0.03N and a substrate growth temperature of 1050 K. Ion channeling experiments show that 90% of Cr sits substitutionally on the cation site. The highest measured magnetization was 1.8B/Cr atom (60% of the expected moment from band theory for ideal material) with the Curie temperature over 900 K. This strongly suggests a link between the CrGa impurity band and ferromagnetism and suggests that a double-exchange-like mechanism is responsible for the ferromagnetic ordering. The transport properties of spin-polarized charge carriers were modeled theoretically taking into account both the Elliott-Yafet and the D'yakonov-Perel' scattering mechanisms. We include the spin-orbit interaction in the unperturbed Hamiltonian and treat scattering by ionized impurities and phonons as a perturbation. Our numerical calculations predict two orders of magnitude longer electron spin relaxation times and an order of magnitude shorter hole spin relaxation times in GaN than in GaAs. First-principles electronic structure calculations predict that efficient spin injection can be achieved using a ferromagnetic GaN:Cr electrode in conjunction with an AlN tunnel barrier. In this structure, the electrode is found to be half-metallic up to the interface and is thus a candidate for high-efficiency magnetoelectronic devices. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
N. Newman and J. E. Medvedeva and L. Gu and S. Krishnamurthy and D. J. Smith and M. van Schilfgaarde and S. Y. Wu and H. X. Liu and R. K. Singh and Z. G. Yu and I. L. Krainsky and A. J. Freeman, "Recent Progress Towards the Development of Ferromagnetic Nitride Semiconductors for Spintronic Applications," Physica Status Solidi (A), John Wiley & Sons, Jan 2006.
The definitive version is available at http://dx.doi.org/10.1002/pssa.200669636
United States. Defense Advanced Research Projects Agency
National Science Foundation (U.S.)
United States. Office of Naval Research
Keywords and Phrases
71.55.Eq; 72.25.-B; 75.50.Pp
Article - Journal
© 2006 John Wiley & Sons, All rights reserved.