A hybrid density functional view of native vacancies in gallium nitride

Gillen, Roland; Robertson, John

doi:10.1088/0953-8984/25/40/405501

Cited by 32 publications

(40 citation statements)

References 47 publications

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“…14, the isolated V Ga also has a deep 3−/2− transition level (2.06 eV above the VBM), and the PL band maximum (if the V Ga is present and behaves as a radiative defect) would be also in infrared. Similar value for the 3−/2− transition level was recently obtained by Gillen and Robertson by using the screened-exchange local density approximation (LDA) method [40]. Thus, neither isolated V Ga nor the V Ga -containing complexes can account for the YL or GL bands in GaN.…”

Section: Gallium Vacancy Complexessupporting

confidence: 81%

Carbon defects as sources of the green and yellow luminescence bands in undoped GaN

et al. 2014

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In high-purity GaN grown by hydride vapor phase epitaxy, the commonly observed yellow luminescence (YL) band gives way to a green luminescence (GL) band at high excitation intensity. We propose that the GL band with a maximum at 2.4 eV is caused by transitions of electrons from the conduction band to the 0/+ level of the isolated C N defect. The YL band, related to transitions via the −/0 level of the same defect, has a maximum at 2.1 eV and can be observed only for some high-purity samples. However, in less pure GaN samples, where no GL band is observed, another YL band with a maximum at 2.2 eV dominates the photoluminescence spectrum. The latter is attributed to the C N O N complex.

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Section: Gallium Vacancy Complexessupporting

confidence: 81%

Carbon defects as sources of the green and yellow luminescence bands in undoped GaN

et al. 2014

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“…Earlier theoretical studies are based on the standard DFT (LDA and GGA) [52][53][54] . Recently hybrid functionals are used increasingly [55][56][57] . Here we studied the complexes made of substitutional carbon and vacancy.…”

Section: Cn − Vgamentioning

confidence: 99%

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

Matsubara

Bellotti

2017

Journal of Applied Physics

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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. CN − CGa, CI − CN and CI − CGa, where CN, CGa and CI denote C substituting nitrogen, C substituting gallium and interstitial C, respectively, and of neighboring gallium/nitrogen vacancies (VGa/VN), i.e. CN − VGa and CGa − VN. 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 were unknown before.

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“…Whereas standard DFT calculations calculated the (2 −/3 −)

V_{Ga}

transition level to be 1.1 eV above the VBM, screened‐exchange LDA (sx‐LDA)] calculations moved the transition levels of

V_{Ga}

deeper into the band gap (i.e., further away from the VBM) (), with the (2 −/3 −) occurring 2.09 eV above the VBM. Optical transitions from the conduction‐band minimum (CBM) would thus be far away from the observed YL band.…”

Section: Gallium Vacancies and Gallium Vacancy Complexes In Ganmentioning

confidence: 99%

“…The authors of Ref. () proposed that the (0/ −) transition level of

V_{Ga}

could be an alternative candidate for causing YL.…”

Section: Gallium Vacancies and Gallium Vacancy Complexes In Ganmentioning

confidence: 99%

First‐principles theory of acceptors in nitride semiconductors

Lyons

Alkauskas

Janotti

et al. 2015

Physica Status Solidi (b)

127

107

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Acceptor defects and impurities play a critical role in the performance of GaN-based devices. Mg is the only acceptor impurity that gives rise to p-type conductivity, while other acceptors (such as C N impurities and V Ga defects) act as sources of compensation and trapping. From the point of view of theory, understanding the physics of acceptor species in GaN has long been a challenge. In the past, limitations of computational techniques made it difficult to quantitatively predict crucial quantities such as thermodynamic and optical transition levels. However, advances in first-principles calculations, including the use of hybrid functionals in density functional theory, have led to a resurgence in efforts to understand properties of acceptors in nitrides. After briefly discussing advances in theoretical techniques, we review recent computational work on acceptor impurities in GaN and compare theoretical results with the available experimental data. We also present new hybrid density functional calculations on the transition levels of V Ga and its complexes with O and H impurities. The results indicate that donor impurities significantly lower V Ga transition levels, and that V Ga -3H and V Ga -O N -2H complexes give rise to yellow luminescence. We also discuss the properties of acceptor impurities in AlN and InN.

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A hybrid density functional view of native vacancies in gallium nitride

Cited by 32 publications

References 47 publications

Carbon defects as sources of the green and yellow luminescence bands in undoped GaN

Carbon defects as sources of the green and yellow luminescence bands in undoped GaN

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

First‐principles theory of acceptors in nitride semiconductors

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