A first-principles study of carbon-related energy levels in GaN. Part I - complexes formed by substitutional/interstitial carbons and gallium/nitrogen vacancies

Abstract

Various forms of carbon based complexes in GaN are studied with first-principles calculations employing Heyd-Scuseria-Ernzerhof hybrid functional within the framework of density functional theory. We consider carbon complexes made of the combinations of single impurities, i.e. ${\mathrm{C}}_{\mathrm{N}}-{\mathrm{C}}_{\mathrm{Ga}}$, ${\mathrm{C}}_{\mathrm{I}}-{\mathrm{C}}_{\mathrm{N}}$ and ${\mathrm{C}}_{\mathrm{I}}-{\mathrm{C}}_{\mathrm{Ga}}$, where ${\mathrm{C}}_{\mathrm{N}}$, ${\mathrm{C}}_{\mathrm{Ga}}$ and ${\mathrm{C}}_{\mathrm{I}}$ denote C substituting nitrogen, C substituting gallium and interstitial C, respectively, and of neighboring gallium/nitrogen vacancies (${\mathrm{V}}_{\mathrm{Ga}}$/${\mathrm{V}}_{\mathrm{N}}$), i.e. ${\mathrm{C}}_{\mathrm{N}}-{\mathrm{V}}_{\mathrm{Ga}}$ and ${\mathrm{C}}_{\mathrm{Ga}}-{\mathrm{V}}_{\mathrm{N}}$. Formation energies are computed for all these configurations with different charge states after full geometry optimizations. From our calculated formation energies, thermodynamic transition levels are evaluated, which are related to the thermal activation energies observed in experimental techniques such as deep level transient spectroscopy. Furthermore, the lattice relaxation energies (Franck-Condon shift) are computed to obtain optical activation energies, which are observed in experimental techniques such as deep level optical spectroscopy. We compare our calculated values of activation energies with the energies of experimentally observed C-related trap levels and identify the physical origins of these traps, which are unknown before.

17 pages, 15 figures, 12 tables. Replacement for published version

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• Band-edge problem in the theoretical determination of defect energy levels: the O vacancy in ZnO as a benchmark case
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Cited by in corpus (4)

• A first-principles study of carbon-related energy levels in GaN: Part II - Complexes formed by carbon and hydrogen, silicon or oxygen
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• Fingerprints of carbon defects in vibrational spectra of gallium nitride (GaN) consider-ing the isotope effect