Impact of Manganese incorporation on the structural and magnetic properties of MOCVD-grown Ga 1-x Mn x N
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Impact of Manganese incorporation on the structural and magnetic properties of MOCVDgrown Ga1-xMnxN Matthew H. Kane1,2, Ali Asghar1, Martin Strassburg1,4, Qing Song3, Adam M. Payne1, Christopher J. Summers2, Z. John Zhang3, Nikolaus Dietz4 and Ian T. Ferguson1 1 Georgia Institute of Technology, School of Electrical and Computer Engineering, Atlanta, GA 30332, U.S.A. 2 Georgia Institute of Technology, School of Materials Science and Engineering, Atlanta, GA 30332, U.S.A. 3 Georgia Institute of Technology, School of Chemistry and Biochemistry, Atlanta, GA 30332, U.S.A. 4 Georgia State University, Department of Physics and Astronomy, Atlanta, GA 30303, U.S.A. * [email protected] ABSTRACT This paper reports the impact of the Mn incorporation on the structural and magnetic properties of Ga1-xMnxN on the metal-organic vapor phase deposition (MOCVD). Crystalline quality and phase purity were determined by high-resolution X-ray diffraction and indicated that no macroscopic second phases are formed during growth. Atomic force microscopy revealed a 2dimensional MOCVD step-flow growth pattern in the Mn-incorporated samples. Various annealing steps were applied to some of the samples to reduce compensating defects and to investigate the effects of post processing on the growth. SQUID measurements showed an apparent ferromagnetic hysteresis behavior. However, none of the requirements for room temperature ferromagnetism in the prevailing mean field DMS theories were found. Therefore, different origins of the ferromagnetic signal are discussed. INTRODUCTION Diluted magnetic semiconductors (DMS) are attractive candidates for the next generation of electronic devices which can exploit both the spin and charge of an electron for computational, logic, and storage operations. These materials consist of a traditional III-V, II-VI, or group IV semiconductor into which a small fraction of a magnetic element, such as interior transition metal like Mn, has been introduced. Some DMS materials can exhibit ferromagnetic behavior under certain doping and processing conditions. These ferromagnetic materials could provide a stable source of spin polarized carriers, which combined with the ease of integration into existing semiconductor technology, may enable future spintronic devices in these DMS systems. Traditional III-V DMS, such as Ga1-xMnxAs, are well-established, though the Curie temperatures of these materials are limited to only around 170K [1]. The ferromagnetic ordering is thought to originate from a long range coupling of the magnetic centers through the free hole carriers [2]. When applying this mean field model to the GaN system, the Curie temperature is predicted to be above room temperature, though this model requires larger substitutional Mn concentrations (~5%) and hole concentrations (3.5x1020) than may be achievable in the Ga1-xMnxN system. Other models have been developed based on first principles density functional theory calculations using the local spin density approximation that also predict ferromagnetism in the
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