Native defects and impurities in GaN

Neugebauer, Jörg; Walle, Chris G. Van de

doi:10.1007/bfb0107538

Cited by 72 publications

(71 citation statements)

References 35 publications

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“…A unique feature of group III nitrides compared to traditional semiconductors is their large ionicity, which has important consequences for the formation of, e.g., surfaces or defects. 27,28 While in binary bulk systems the electrostatic interaction can be partially described by the next nearest neighbor coupling within the Keating parameters this is not possible for ternary alloys where the specific arrangement of cations determines the electrostatic energy. We will therefore study in the following how the Keating model can be extended to account for electrostatic interactions.…”

Section: Valence Force Field Modelsmentioning

confidence: 99%

Limits and accuracy of valence force field models forInxGa1−xNalloys

Grosse

Neugebauer

2001

Phys. Rev. B

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Formation energies, equilibrium geometries, and elastic properties of ordered In x Ga 1Ϫx N structures have been calculated employing density funcional theory. Based on these results, limits and accuracy of several valence force field ͑VFF͒ models are compared. While these empirical models have been shown to work reasonably well to describe zincblende III/V semiconductors we find significant deviations for group III nitrides ͑GaN, InN͒ and their alloys. We therefore propose a new model that correctly takes into account the long-range electrostatic interactions. Although only the elastic constants of the binary zincblende compounds and the formation energy difference to wurtzite are used as input, the model correctly describes the formation energies and structure of wurtzite binary compounds and ternary alloys.

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Section: Valence Force Field Modelsmentioning

confidence: 99%

Limits and accuracy of valence force field models forInxGa1−xNalloys

Grosse

Neugebauer

2001

Phys. Rev. B

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“…We consider first the H-assisted incorporation suggested recently [2] for Mg. The formation energy of a (neutral) Be-H complex in its equilibrium configuration in GaN is 0.32 (0.87) eV/complex in N-rich (Ga-rich) conditions (solubility limits: Be 3 N 2 and H 2 molecules): the concurrent incorporation of Be and H in GaN is therefore efficient.…”

Section: Gamentioning

confidence: 99%

“…Si Ga is a suitable shallow donor, but the quest for the optimal acceptor still continues. The current-best p-dopant [1] is Mg Ga , with which hole concentrations in the 10 17 cm −3 range have been achieved at room temperature (despite its ionization energy of ∼ 0.2 eV), and whose activation mechanism is still under scrutiny [2].We show here that substantial improvements can be achieved by doping GaN with Be: ab initio calculations of formation energies, impurity levels, and atomic geometries of Be in GaN show that Be is the shallowest acceptors reported so far in GaN. Calculated solubilities indicate barely acceptable doping levels in N-rich growth conditions at high growth temperatures, while complete compensation occurs in Ga-rich conditions due to N vacancies.…”

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“…V + N is an ionized single donor with a formation energy of 2.32 + µ e (possibly behaving as multiple donor in the extreme p limit [2]). The Be interstitials are double donors over most of the relevant Fermi level range (since ǫ[2 + /+] ∼ 2.3 eV), with formation energies of 2.39 eV + 2 µ e (cage) and 2.43 eV + 2 µ e (channel).…”

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Theoretical evidence for efficient p-type doping of GaN using beryllium

Bernardini

Fiorentini

Bosin³

1997

Applied Physics Letters

104

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Ab initio calculations predict that Be is a shallow acceptor in GaN. Its thermal ionization energy is 0.06 eV in wurtzite GaN; the level is valence resonant in the zincblende phase. Be incorporation is severely limited by the formation of Be3N2. We show however that co-incorporation with reactive species can enhance the solubility. H-assisted incorporation should lead to high doping levels in MOCVD growth after post-growth annealing at about 850 K. Be-O co-incorporation produces high Be and O concentrations at MBE growth temperatures.PACS numbers : 71.25. Eq, 61.72.Vv, 61.72.Ss Gallium nitride is a base material for green-to-UV optoelectronics, and piezoelectric and high-power devices. For these applications, controllable doping is an obvious necessity. Si Ga is a suitable shallow donor, but the quest for the optimal acceptor still continues. The current-best p-dopant [1] is Mg Ga , with which hole concentrations in the 10 17 cm −3 range have been achieved at room temperature (despite its ionization energy of ∼ 0.2 eV), and whose activation mechanism is still under scrutiny [2].We show here that substantial improvements can be achieved by doping GaN with Be: ab initio calculations of formation energies, impurity levels, and atomic geometries of Be in GaN show that Be is the shallowest acceptors reported so far in GaN. Calculated solubilities indicate barely acceptable doping levels in N-rich growth conditions at high growth temperatures, while complete compensation occurs in Ga-rich conditions due to N vacancies. We show however that the co-incorporation of Be with H or O strongly enhances its solubility (otherwise limited by the formation of Be nitride) and may lead to p-type doping.Method -By means of density-functional-theory (DFT) [3] ultrasoft-pseudopotential plane-wave calculations of total energies and forces in doped GaN (details are reported elsewhere [1,4,5]), we predict from first principles the formation energies and thermal ionization energies, and ensuing dopant and carrier concentrations of Be in GaN. The carriers concentration at temperature T due to a single acceptor with thermal ionization energyThe impurity concentration D in thermal equilibrium isfor a growth temperature of T g , with N s = 4.33×10 22 cm −3 available sites, and a formation energy E form . Omission of the entropic factor exp (S f /k B ) (formation entropies are currently impossible to calculate reliably) does not alter our conclusions. The formation energy for Be Ga in charge state Q iswhere µ e is the electron chemical potential, E tot (Q) is the total energy of the defected supercell in charge state Q, E Q v its top valence band energy, n X and µ X the number of atoms of the involved species (X=Ga, N, Be) and their chemical potentials. The latter potentials must satisfy the equilibrium conditions with GaN and Be-X compounds. To obtain maximum solubility, we will always be choosing the highest µ Be compatible with the relevant solubility limit. Then, a single chemical potential (e.g. µ N ) remains to be determined by the i...

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