Transition metal doped GaN based diluted magnetic semiconductors are very attractive candidate for future "spintronics" devices based on carrier-induced ferromagnetism. Theoretical calculations predicted that Cr-doped GaN was found to have the most stable ferromagnetic state in transition metal doped GaN. Up to now, Cr-doped GaN layers have been grown only by molecular beam epitaxy. Although metal organic vapor phase epitaxy (MOVPE) is a mature technique regarding the layer quality, no growth of Cr-doped GaN layers by MOVPE has been reported, yet. In this study we investigate the growth of Cr-doped GaN layers by MOVPE and their characterization. Conventional Ga and N precursors were used while bis(cyclopentadienyl)chromium (Cp₂Cr) was employed as the Cr precursor. The influence of precursors supply, carrier gas type and growth temperature on Cr incorporation efficiency in the GaN layers will be discussed. Secondary ion mass spectrometry (SIMS) was used to verify the incorporated Cr fraction in the layers. A linear dependence between mole fraction of Cp₂Cr in gas phase and incorporated Cr in solid phase was found. So far Cr-doped GaN layers with Cr concentrations in solid phase up to 2 ´ 10¹⁹ at/cm^-3 were grown. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL) measurements were performed to investigate the surface morphology, structural and optical properties of these layers. Superconducting quantum interference device (SQUID) zero field heating measurements showed a remanent magnetization even above room temperature for the Cr-doped GaN layers.

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1. Confocal Raman microscopy of the strain AlGaN/GaN heterostructures on sapphire
2. An old technique (Umweganregungen) for X-ray characterization of an epitaxial new material ( Chromium doped GaN)
3. MOVPE growth and in situ characterization of GaN layers