Abstract
Carbon (C) doping is essential for producing semi-insulating GaN for power electronics. However, to date the nature of C doped GaN, especially the lattice site occupation, is not yet well understood. In this work, we clarify the lattice site of C in GaN using polarized Fourier-transform infrared and Raman spectroscopies, in combination with first-principles calculations. Two local vibrational modes (LVMs) at 766 and in C doped GaN are observed. The mode is assigned to the nondegenerate mode vibrating along the axis, whereas the mode is ascribed to the doubly degenerate mode confined in the plane perpendicular to the axis. The two LVMs are identified to originate from isolated with local symmetry. Experimental data and calculations are in outstanding agreement both for the positions and the intensity ratios of the LVMs. We thus provide unambiguous evidence of the substitutional C atoms occupying the N site with a charge state in GaN and therefore bring essential information to a long-standing controversy.
- Received 20 May 2018
DOI:https://doi.org/10.1103/PhysRevLett.121.145505
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