Defects at nitrogen site in electron-irradiated AlN

Son, N. T.; Gali, Ádám; Szabó, Áron; Bickermann, Matthias; Ohshima, Takeshi; Isoya, Junichi; Janzén, Erik

doi:10.1063/1.3600638

Cited by 12 publications

(13 citation statements)

References 14 publications

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“…These findings indicate that the S = 3/2 state of V N 2− might be of potential interest as a defect qubit, but it might be difficult to realize, as highly n- doped w- AlN is difficult to obtain 47 48 . Interestingly, the V N 0 S = 1/2 state has been recently detected using electron paramagnetic resonance 18 19 . Based on these results, we considered the Fermi level range in the vicinity of the stability region of V N 0 , which might be accessible in experiments.…”

Section: Resultsmentioning

confidence: 99%

“…We found that negatively charged nitrogen vacancies exhibit localized spin-triplet states in n- type aluminum nitride under realistic strain conditions. Nitrogen vacancies are naturally incorporated in aluminum nitride during crystal growth and they are known to be the main source of the intrinsic n- type behavior of aluminum nitride 18 19 20 21 , thus making the nitrogen vacancy spins easily amenable to experimental investigations 18 19 . Extra n- type doping control might be achievable by introducing substitutional oxygen impurities (O N ) during crystal growth 24 .…”

Section: Discussionmentioning

confidence: 99%

“…Numerical convergence in terms of the energy cutoff, the k-point sampling, and the supercell size was checked, with a numerical error in the hyperfine tensor less than 10 MHz. To verify the accuracy of the PBE functional, we calculated the hyperfine parameters of the neutral V N spin (S = 1/2) and compared them to previous theoretical and experimental results 18 as shown in Table 2 . We found an excellent agreement between our and previous results.…”

Section: Methodsmentioning

confidence: 99%

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Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

Seo

Govoni

Galli

2016

Sci Rep

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Spin defects in wide-band gap semiconductors are promising systems for the realization of quantum bits, or qubits, in solid-state environments. To date, defect qubits have only been realized in materials with strong covalent bonds. Here, we introduce a strain-driven scheme to rationally design defect spins in functional ionic crystals, which may operate as potential qubits. In particular, using a combination of state-of-the-art ab-initio calculations based on hybrid density functional and many-body perturbation theory, we predicted that the negatively charged nitrogen vacancy center in piezoelectric aluminum nitride exhibits spin-triplet ground states under realistic uni- and bi-axial strain conditions; such states may be harnessed for the realization of qubits. The strain-driven strategy adopted here can be readily extended to a wide range of point defects in other wide-band gap semiconductors, paving the way to controlling the spin properties of defects in ionic systems for potential spintronic technologies.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

Seo

Govoni

Galli

2016

Sci Rep

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“…Since the transformation from the shallow donor to the deeper DX state typically requires to overcome a thermal barrier of some 10 to a few 100 meV, at low sample temperatures the donor can remain for a while in its unstable high symmetry shallow state and lead to “persistent photoconductivity” (PPC) after illumination. The influence of the silicon donor related DX centres on the thermal stability of the shallow donor state with S = ½ was also found in electron paramagnetic resonance . Since for the axial symmetry of AlGaN two possible distortions − parallel to and off the

\overset{trueˆ}{normalc}

‐axis − might occur, two DX states with different relaxation energies are expected.…”

Section: Introductionmentioning

confidence: 84%

Optical signatures of silicon and oxygen related DX centers in AlN

Thonke

Lamprecht

Collazo

et al. 2017

Phys. Status Solidi A

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Bulk AlN crystals typically contain high concentrations of oxygen, silicon, and carbon À as also state-of-the art epitaxial layers typically do, depending on the specific growth conditions. In optical spectroscopy, such crystals show broad bands in the region from 2-5 eV in absorption and emission. We investigated several emission bands in the range from 1.4 to 1.9 eV, especially those centred at 2.0 and 2.4 eV, which under below-bandgap excitation with a 325 nm laser dominate the photoluminescence (PL) spectra both at low and at room temperature. We find clear indications that all these transitions occur between different states of the shallow donors Si or O, and deep acceptors. The donors undergo lattice relaxation and form DX centres. Depending on temperature, the initial state is either a long-lived (S ¼ 1) DXcentre state of the donors, a shallow EMT-like conventional donor state, or a free electron À with markedly different relaxation times for the optical transitions under below-bandgap excitation. The acceptor involved in these PL bands is likely linked to aluminum vacancies. Based on our data, we develop configuration coordinate diagrams and a combined level scheme for multiple transitions in the range from 1.4 to 2.4 eV.Tentative level scheme for PL bands observed in AlN in the range from 1.4 to 2.4 eV.

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“…4 In addition, defects on the nitrogen sublattice (either O N or V N ) have been observed by electron paramagnetic resonance (EPR). 5,6 All these defects are expected to introduce defect states in the band gap of AlN (which is 6.2 eV wide); they may cause sub-band-gap light absorption that can interfere with the operation of optoelectronic devices. Despite these initial assignments, an explanation of the various experimental results based on detailed microscopic mechanisms has yet to emerge.…”

Section: Origins Of Optical Absorption and Emission Lines In Alnmentioning

confidence: 99%

Origins of optical absorption and emission lines in AlN

Yan

Janotti

Scheffler

et al. 2014

Applied Physics Letters

150

117

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To aid the development of AlN-based optoelectronics, it is essential to identify the defects that cause unwanted light absorption and to minimize their impact. Using hybrid functional calculations, we investigate the role of native defects and their complexes with oxygen, a common impurity in AlN. We find that Al vacancies are the source of the absorption peak at 3.4 eV observed in irradiated samples and of the luminescence signals at 2.78 eV. The absorption peak at ∼4.0 eV and higher, and luminescence signals around 3.2 and 3.6 eV observed in AlN samples with high oxygen concentrations are attributed to complexes of Al vacancies and oxygen impurities. We also propose a transition involving Al and N vacancies and oxygen impurities that may be a cause of the absorption band peaked at 2.9 eV

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Defects at nitrogen site in electron-irradiated AlN

Cited by 12 publications

References 14 publications

Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

Design of defect spins in piezoelectric aluminum nitride for solid-state hybrid quantum technologies

Optical signatures of silicon and oxygen related DX centers in AlN

Origins of optical absorption and emission lines in AlN

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