The Effect of Mn Concentration on Curie Temperature and Magnetic Behavior of MOCVD Grown GaMnN Films
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J7.3.1
The Effect of Mn Concentration on Curie Temperature and Magnetic Behavior of MOCVD Grown GaMnN Films Erkan Acar Berkman1, Mason J. Reed1, F. Erdem Arkun1, Nadia A. El-Masry1, John M. Zavada2, M. Oliver Luen3, Meredith L. Reed3, Salah M. Bedair3. 1Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, 27695 2Army Research Office, Research Triangle Park, Durham, North Carolina, 27709 3Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina, 27695
ABSTRACT We report on the growth and characterization of dilute magnetic semiconductor GaMnN showing ferromagnetism behavior above room temperature. GaMnN films were grown by MOCVD using (EtCp2)Mn as the precursor for in-situ Mn doping. Structural characterization of the GaMnN films was achieved by XRD, SIMS and TEM measurements. XRD and TEM confirmed that the films were single crystal solid solutions without the presence of secondary phases. SIMS analysis verified that Mn was incorporated homogeneously throughout the GaMnN layer which was ~0.7µm thick. Ferromagnetic behavior for these films was observed along the c-direction (out of plane orientation) in a Mn concentration range of 0.025-2%. The saturation magnetization ranged from 0.18-1.05 emu/cc for different growth conditions. Curie temperatures of the GaMnN films were determined to be from 270 to above 400K depending on the Mn concentration. This dependence of Curie temperature on concentration of Mn in GaMnN indicates that the grown films are random solid solutions. SQUID measurements ruled out the possibility of spin-glass and superparamagnetism in these MOCVD grown GaMnN films. The grown films were electrically semi-insulating; however PL measurements showed that the films were still optically active after Mn doping. This study showed that the growth of III-Nitride films doped with Mn requires a small window of growth conditions that depend on growth temperature and (EtCp)2Mn flux to achieve ferromagnetism above room temperature, and the magnetic response of the film depends on the Fermi level position. We suggest that ferromagnetism occurs when the Fermi level lies within the Mn energy level which is 1.4 eV above the GaN valence band. INTRODUCTION The current integrated circuits and electronic devices are operated by controlling the flow of carriers (electrons or holes) through the semiconductor material, i.e. these conventional devices are based on controlling only the charge of the electrons. The main objective of making a ferromagnetic semiconductor is to utilize the spin of the electrons as well as their charge, thus manufacturing a device which will enable processing and data storage simultaneously. Considerable attention has been focused on the III-V DMS materials since the first DMS reported by Munekata et al. [1], and subsequent studies predicting Curie temperatures above room temperature for GaN [2-4]. Reed et al. produced the first GaMnN material with a ferromagnetic ordering above 300K via soli
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