Optical Transmission Measurements on MOCVD Grown GaMnN Films on Sapphire
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Optical Transmission Measurements on MOCVD Grown GaMnN Films on Sapphire Fevzi Erdem Arkun1, Nadia A El-Masry2, John Muth3, Xiyao Zhang4, Amr Mahrouse3, John Zavada5, and Salah M Bedair3 1 Materials Science and Engineering, North Carolina State University, 4327 Avent Ferry Rd Apt 4, Raleigh, NC, 27606 2 Materials Science and Engineering, North Carolina State University, Raleigh, NC, 27695 3 Electrical and Computer Engineering, North Carolina State University, Raleigh, NC, 27695 4 Physics, North Carolina State University, Raleigh, NC, 27695 5 Army Research Office, Durham, NC, 27709
ABSTRACT We demonstrate optical transmission measurements performed on 1.2 µm thick GaMnN films grown by metalorganic chemical vapor deposition on (0001) sapphire substrates. According to the data acquired from these measurements, Mn forms a deep acceptor band at 1.4 eV above the valance band of GaMnN. Full width at half maximum of this absorption band increases from 107 meV to 198meV as the Mn concentration increases from 0.3% to 1.6 %; which indicates that this band becomes wider as the concentration of Mn increases in the lattice. A broad absorption band starting at 1.9eV and extending to the band edge of GaMnN was also determined. This was attributed to the transition from the Mn energy band to the conduction band edge of GaMnN. Absorption at both of these bands scales with the Mn concentration and thickness of the films. The effect of co-doping of GaMnN films with magnesium on the transmission spectra was also investigated. The absorption band initially observed at 1.4 eV was shifted to 1.6 eV as a result of introduction of Magnesium into the lattice of GaMnN. From these results we conclude that Mn is incorporated in the lattice and forms an energy band in the bandgap of GaMnN. The width of this energy band is also a function of the Mn concentration in GaMnN.
INTRODUCTION Spin based electronics or spintronics utilizes the spin of carriers in addition to the charge of carriers to create new functionalities in devices. Dilute Magnetic Semiconductors (DMSs) can show ferromagnetic ordering above room temperature and are compatible with current growth and device fabrication technologies. The development and understanding of DMSs are very important in order to achieve spintronics device structures. According to a mean field model, the ferromagnetic ordering temperature for GaMnN is above room temperature for a Mn concentration of 5% Mn and a hole concentration of 3.5 x 1020 /cm3 [1]. In this model the spins of the delocalized carriers couple antiferromagnetically with the spins of the localized Mn ions in the lattice thereby creating long range ferromagnetic ordering among Mn ions. The properties of GaMnN films that are co-doped with silicon and magnesium have been studied in detail previously[2]. In this study the optical properties of these films are investigated in relation to co-
doping and compared with their magnetic properties. A correlation between optical and magnetic properties has been determined as a result of t
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