Electronic properties of (Ga,Mn)N thin films with high Mn content

MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand
Journal of Applied Physics (Impact Factor: 2.21). 12/2008; DOI:10.1063/1.3020536
Source: IEEE Xplore

ABSTRACT Optical and dc resistivity measurements as well as x-ray spectroscopies have been performed on (Ga,Mn)N films containing Mn at up to 11 at . % . The results indicate that at higher Mn contents, the Fermi level is situated within extended states, while GaN host interband optical transitions are unaffected. The Mn state is confirmed to be 3d5 , as in the case of lower Mn content films; however, the high Mn content merges the 3d levels into a band located just below the host conduction band. The Fermi level is located within these Mn states just below the conduction band, in sharp contrast to its midgap position in fully crystalline, low Mn concentration materials. The difference in the position of the Fermi level at high Mn dopant levels has important implications for the promotion of ferromagnetism in this material.

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    ABSTRACT: Amorphous GaN films have been deposited onto various substrates by ion-assisted deposition. The films were deposited at room temperature using nitrogen ion energies in the range 40-900 eV. Rutherford backscattering spectroscopy and nuclear reaction analysis show that the Ga:N atomic ratio is approximately one for films grown with ion energy near 500 eV; these films have the highest transparency. Films grown with ion energies below 300 eV are Ga rich, and show reduced transparency across the visible. Raman spectroscopy, x-ray diffraction, and transmission electron microscopy confirm the amorphous nature of the films. Annealing studies on a-GaN establish that the films begin to crystallise at a temperature of about 700 C. To investigate the local bonding environment of the Ga or N atoms, we have measured the extended x-ray absorption fine structure (EXAFS) of the transparent GaN films. The EXAFS results indicate that the films are dominated by heteropolar tetrahedral bonding, with a low density of homopolar bonds.
    MRS Proceedings. 12/2000; 693.

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