Mn- and Fe- doped GaN for spintronic applications
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1040-Q06-09
Mn- and Fe- doped GaN for spintronic applications Enno Malguth1,2, Axel Hoffmann1, Stefan Werner1, Matthew H. Kane3, and Ian T. Ferguson3 1 Institut für Festkörperphysik, Technische Universität Berlin, Berlin, 10623, Germany 2 Microstructural Analysis Unit, University of Technology Sydney, Sydney, 2007, Australia 3 School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA, 30332-0245 ABSTRACT In the context of ferromagnetic spin-coupling in dilute magnetic semiconductors, we present optical investigations on Mg co-doped GaMnN and Fe doped GaN. A complex luminescence feature occurring in Mg co-doped GaMnN around 1 eV was previously attributed to the internal 4T2(F) —4T1(F) transition of Mn4+ involved in different complexes. Selective excitation studies indicate the presence of at least three different complexes. Photoluminescence excitation spectra suggest that the internal Mn3+ transition may represent an excitation mechanism. Magneto photoluminescence spectra indicate equal g values for the ground and excited state. Low temperature infrared absorption spectra of Fe doped GaN allow to unambiguously establish the electronic structure of the Fe2+ center in GaN. Our results suggest that the Fe2+(5T2) state is stabilized against Jahn-Teller coupling by the reduced site-symmetry of the hexagonal lattice. INTRODUCTION Recent studies predict a high potential of a ferromagnetic spin-coupling at room temperature for GaMnN with a high concentration of free holes [1, 2, 3]. In accordingly prepared Mg doped GaMnN material, a rich luminescence structure was detected around 1 eV and attributed to the internal spin allowed Mn4+(4T2(F) —4T1(F)) transition [4, 5]. This interpretation is supported by theoretical considerations suggesting that the Mn3+/4+ donor level is found within the band gap of GaN [6]. As a consequence, Mn incorporation should compensate p-type doping in GaN rendering hole mediated spin-coupling rather difficult to achieve in GaMnN. Until now, no unambiguous evidence could be given that the luminescence feature around 1 eV actually originates from Mn4+. Also bound states consisting of a hole bound to an ionized TM center (A-) may play an important role for ferromagnetic spin-coupling [8]. Such a state has been observed in GaN involving Fe2+[9, 10]. For a good understanding of this effective-mass-like state the electronic structure of the involved Fe2+ center needs to be known. In this work, we present infrared absorption spectra recorded at liquid helium temperatures. These results confirm the electronic structure of the Fe2+ center in GaN that had been established on the basis of measurements at 40 K [11]. These results allow conclusions about the axial distortion of the tetrahedral crystal field in the hexagonal crystal as well as about the Jahn-Teller coupling affecting the Fe center.
Mg co-doped GaMnN 19 -3 Mn: 1.5%, Mg: 1 x 10 cm
PL-Intensity (arb. units)
1.8 K exc.: 1.72 eV
exc.: 2.41 eV
exc.: 2.54 eV
0.90
0.95
1.00
1.05
Energy (eV) Figure 1. PL spectr
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