Structural and Magnetic Characterization of MOCVD Grown GaMnN and GaFeN Nanostructures
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Structural and Magnetic Characterization of MOCVD Grown GaMnN and GaFeN Nanostructures Shalini Gupta1, Hun Kang1, Matthew H. Kane1,2, Eun Hyun Park1, and Ian T. Ferguson1,2 1 School of Electrical and Computer Engineering, Georgia Institute of Technology, 777 Atlantic Dr., Atlanta, GA, 30332-0250 2 School of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Dr., Atlanta, GA, 30332-0245 Abstract The growth of Ga1-xMnxN and Ga1-xFexN nanostructures was carried out by MOCVD. Introduction of transition metals (TM) Mn and Fe in GaN nanostructures enhanced the nucleation of the nanostructures resulting in reduced lateral dimensions and increased nanostructure density. The Ga1-xMnxN nanostructures showed hysteresis behavior at 5K. Room temperature ferromagnetism was obtained in the Ga1-xFexN nanostructures unlike its bulk counterpart. This paper presents the growth and magnetization study of Ga1-xTMxN nanostructures. These structures could be used to enhance the efficiency of spintronic devices. Introduction The developing field of spintronics seeks to exploit the spin property of the electron in addition to its charge. This could lead to the integration of electro-magneto-optical properties into devices. The realization of these devices, such as reconfigurable logic elements [1] and circularly polarized light emitting diodes [2], requires new materials which can support both the storage and transport of spin-polarized carriers. Diluted magnetic semiconductors (DMS) are ideal in this regard, as they can exhibit ferromagnetism in materials compatible with those used for modern solid state electronics and optoelectronics. In the Arsenide system, GaAs doped with Manganese (Mn) has been widely studied. This material shows magnetic properties at relatively low temperatures with the highest reported Curie temperature (Tc) of 110 K although normally quoted values are about 50-60 K [3, 4]. This low Tc does not make the device feasible for practical application. For practical devices, it is essential that the ferromagnetism be retained at room temperature. Further, it is advantageous if the DMS that is employed can be easily incorporated into existing applications. In this regard, the III-Nitrides will be excellent for room temperature (RT) spintronic application because recent theoretical predictions and experimental data show that Ga1-xMnxN has a Tc higher than RT [5]. Several studies have been done on bulk GaN doped with transition metal (TM). However, there are not many published reports of ferromagnetism in GaN quantum dots (QDs). Studies in the Arsenides have shown that a higher Tc can be obtained by using ferromagnetic QDs [6, 7]. Further, longer carrier spin-relaxation times have been reported in QDs. Carrier confinement within a QD is expected to strengthen carrier localization and subsequently enhance the thermal stability of magnetic polarons. Higher spin injection efficiencies are expected by
using ferromagnetic QDs [6]. In addition, QDs have been shown to improve the efficiency
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