Ferromagnetic GaN based structures for room temperature spintronics: spin dynamics and spin interactions

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The observation of ferromagnetism of GaN:Gd and even GaN:Cu in SQUID measurements is still not well understood. We will perform sensitive static measurements of the magnetooptical Kerreffect to check if this (phantom) ferromagnetism has an influence on the conduction band and if it may be useful for applications in spin aligners. We will continue our time-resolved measurements on spin relaxation in wurtzite GaN based materials to explore heterostructures for improved spin lifetimes. These studies will be extended to the metastable cubic phase of GaN, where we will perform the first measurements on cubic GaN quantum wells and superlattices motivated by our recent findings of ns-spinlifetimes in bulk c-GaN at room temperature. Our preliminary results indicate open questions in cubic GaN like a weak temperature dependence or strong spatial variations of the spin lifetime. We plan spatial correlation of µ-photoluminescence data with spin lifetime data and time-resolved photoluminescence measurements to clarify e.g. the influence of the ever present hexagonal inclusions in cubic structures.