Tri-carbon defects in carbon doped GaN
K. Irmscher1, I. Gamov1, E. Nowak1,2, G. Gärtner3, F. Zimmermann4, F.C. Beyer4, E. Richter5, M. Weyers5, and G. Tränkle5
Published in:
Appl. Phys. Lett., vol. 113, no. 26, pp. 262101 (2018).
Abstract:
Carbon doped GaN crystals grown by hydride vapor phase epitaxy have been investigated using mid-infrared and near-ultraviolet absorption spectroscopy. Two local vibrational modes (LVMs) at 1679 cm-1 and 1718 cm-1 as well as an absorption shoulder in front of the band edge absorption of GaN are discovered, all of which increase in intensity with the carbon concentration. The LVMs are similar in wavenumber position to an LVM formerly observed in carbon-rich AlN crystals and unambiguously assigned to a tri-carbon defect. Together with the polarization dependence of the LVMs, we conclude that in GaN the underlying defects are two crystallographically inequivalent configurations of each three nearest neighbor carbon atoms. The strength of both the infrared and ultraviolet absorption features implies concentrations of the underlying defects of the same order as the total carbon concentration. Hence, the tri-carbon defects contribute to the UV absorption and possess deep energy levels in GaN.
1 Leibniz-Institut für Kristallzüchtung, Max-Born-Strasse 2, 12489 Berlin, Germany
2 Faculty of Technical Physics, Politechnika Poznanska, Piotrowo 3, 60-965 Poznan, Poland
3 Institute of Experimental Physics, TU Bergakademie Freiberg, 09599 Freiberg, Germany
4 Institute of Applied Physics, TU Bergakademie Freiberg, 09599 Freiberg, Germany
5 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Strasse 4, D-12489 Berlin, Germany
Copyright © 2018 AIP Publishing LLC. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the AIP Publishing LLC.
Full version in pdf-format.