Ab initio calculation of the formation energy of charged vacancies in germanium

Śpiewak, Piotr; Sueoka, Koji; Vanhellemont, Jan; Kurzydłowski, K. J.; Młynarczyk, Krzysztof; Wabiński, P.; Romandic, Igor

doi:10.1016/j.physb.2007.08.147

Cited by 23 publications

(15 citation statements)

References 35 publications

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“…where µ e is the electronic chemical potential measured with respect to energy position of the valence band maximum E v [63]. Our calculated formation energies are constrained to vary with respect to the position of the Fermi level (electronic potential µ e ) ranging from 0 eV to 5.10 eV (experimental band gap [1,11,12] We further calculated the transition energy levels ε (q/q ) of the Si substitutional complexes using the following expression [62]; Only the line segments that correspond to the lowest energy charge states are shown.…”

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confidence: 99%

Defect charge states in Si doped hexagonal boron-nitride monolayer

Mapasha

Molepo

Andrew

et al. 2016

J. Phys.: Condens. Matter

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We perform ab-initio density functional theory calculations to investigate the energetics, electronic and magnetic properties of isolated stoichiometric and non-stoichiometric substitutional Si complexes in a hexagonal boron-nitride monolayer. The Si impurity atoms substituting the boron atom sites Si B giving non-stoichiometric complexes are found to be the most energetically favourable, and are half-metallic and order ferromagnetically in the neutral charge state. We find that the magnetic moments and magnetization energies increase monotonically when Si defects form a cluster. Partial density of states and standard Mulliken population analysis indicate that the half-metallic character and magnetic moments mainly arise from the Si 3p impurity states. The stoichiometric Si complexes are energetically unfavorable and non-magnetic.When charging the energetically favourable non-stoichiometric Si complexes, we find that the formation energies strongly depend on the impurity charge states and Fermi level position. We also find that the magnetic moments and orderings are tunable by charge state modulation q = -2, -1, 0, +1, +2. The induced half-metallic character is lost (retained) when charging isolated (clustered) Si defect(s). This underlines the potential of a Si doped hexagonal boron-nitride monolayer for novel spin-based applications.

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Section: Resultsmentioning

confidence: 99%

Defect charge states in Si doped hexagonal boron-nitride monolayer

Mapasha

Molepo

Andrew

et al. 2016

J. Phys.: Condens. Matter

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“…The obtained results are compared with those previously obtained using the LDAþU approach 21,22 and with results from literature when useful. It will be shown that using the HSE06 approach yields not only a more accurate electronic description of vacancies but also a good estimate for the activation energy of self-diffusion in Ge, which is consistent with experimental data.…”

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confidence: 87%

“…9-13) (as a review, see Refs. 10-12, and references therein), a multitude of ab initio calculations have been published [14][15][16][17][18][19][20][21][22] mostly based on the density functional theory (DFT). Unfortunately, almost all theoretical supercell calculations based on the local density or generalized gradient approximation (LDA or GGA) suffer from an important shortcoming of DFT, namely the failure to reproduce well the bandgap of semiconductors and insulators.…”

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confidence: 99%

“…23 The underestimation of the bandgap leads to uncertainties not only in the calculated formation and activation energies of point defects but also of the associated defect levels in the bandgap. 24 In the case of Ge, a closing of the bandgap is even observed for well-converged DFT calculations 21 predicting thus a metallic ground state that obviously does not correspond with reality. Using the LDAþU approach 25,26 leads to a small bandgap 21,22 by adding an orbital-dependent term in a (screened) Hartree-Fock (HF) like manner to the LDA potential.…”

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confidence: 99%

“…24 In the case of Ge, a closing of the bandgap is even observed for well-converged DFT calculations 21 predicting thus a metallic ground state that obviously does not correspond with reality. Using the LDAþU approach 25,26 leads to a small bandgap 21,22 by adding an orbital-dependent term in a (screened) Hartree-Fock (HF) like manner to the LDA potential. Another way to obtain a bandgap is the application of a certain fraction of exact (Hartree-Fock) exchange within the DFT approach via a socalled hybrid functional.…”

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confidence: 99%

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Improved calculation of vacancy properties in Ge using the Heyd-Scuseria-Ernzerhof range-separated hybrid functional

Śpiewak

Vanhellemont

Kurzydłowski

2011

Journal of Applied Physics

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Electronic and magnetic properties of Mn ∕ Ge digital ferromagnetic heterostructures: An ab initio investigation J. Appl. Phys. 99, 08D705 (2006); 10.1063/1.2172542 Energy band gaps and lattice parameters evaluated with the Heyd-Scuseria-Ernzerhof screened hybrid functional Efficient hybrid density functional calculations in solids: Assessment of the Heyd-Scuseria-Ernzerhof screened Coulomb hybrid functionalThe revised Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE06) is used for calculating the formation and migration energies of the vacancy in Ge, and the results are compared with those previously obtained using the local density approximation with the on-site Coulomb interaction U (LDAþU) approach and with other published results. It is demonstrated that using HSE06 gives a much more accurate electronic description of the vacancy and yields an excellent estimate of the activation energy of self-diffusion in Ge consistent with experimental data. The migration energies of the vacancy in different charge states calculated with the HSE06 approach agree well with the results of low-temperature infrared-absorption measurements. In contrast to previous results, the HSE06 calculations suggest that vacancies in Ge are multiple-level acceptors with levels located in the upper half of the bandgap. This can explain the observed high density of acceptor-like interface traps near the conduction band, pinning the Fermi level and inhibiting the formation of an inversion layer in n-channel devices in Ge.

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Intrinsic Defects: Ionization Thermodynamics

Charged Semiconductor Defects

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Ab initio calculation of the formation energy of charged vacancies in germanium

Cited by 23 publications

References 35 publications

Defect charge states in Si doped hexagonal boron-nitride monolayer

Defect charge states in Si doped hexagonal boron-nitride monolayer

Improved calculation of vacancy properties in Ge using the Heyd-Scuseria-Ernzerhof range-separated hybrid functional

Intrinsic Defects: Ionization Thermodynamics

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