Direct Measurement of Polarization-Induced Fields in GaN/AlN by Nano-Beam Electron Diffraction

Carvalho, Daniel; Müller‐Caspary, Knut; Schowalter, Marco; Grieb, Tim; Mehrtens, Thorsten; Rosenauer, A.; Ben, T.; Garcı́a, R.; Redondo-Cubero, A.; Lorenz, K.; Daudin, B.; Morales, F. M.

doi:10.1038/srep28459

Cited by 26 publications

(11 citation statements)

References 42 publications

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“…The g value relates the applied field and radiation energy for a particular absorption and can provide information about the type and surrounding environment of the free electrons detected in the experiment. For GaN, there is little recent work employing EPR for defect identification, although there are some prior studies indicating the g values for certain defects in bulk GaN. − In our tests, we identified one prominent defect at a g value of 2.008 ± 0.0005, as shown in Figure . g values of around 2.008 have been associated with N vacancies and also with Ga vacancies .…”

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confidence: 58%

Nonthermal Plasma Synthesis of Gallium Nitride Nanoparticles: Implications for Optical and Electronic Applications

Mandal

Lunt

et al. 2021

ACS Appl. Nano Mater.

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Group III nitrides, such as gallium nitride (GaN), play an important role in electroluminescent devices and power electronics. They are also increasingly used as photocatalysts and battery materials. In pursuit of increased flexibility and reduced cost, there are many attempts to synthesize these materials in nanocrystal form via a range of methods. In this work, we demonstrate the synthesis of GaN nanocrystals using radiofrequency nonthermal plasma. This method allows for control over both the crystallinity of the nanoparticles and their size. In addition, we see little change in the surface composition upon exposure to air, as evaluated using Fourier transform infrared spectroscopy. These results point to the promise of this method for effective group III nitride nanoparticle synthesis.

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confidence: 58%

Nonthermal Plasma Synthesis of Gallium Nitride Nanoparticles: Implications for Optical and Electronic Applications

Mandal

Lunt

et al. 2021

ACS Appl. Nano Mater.

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“…The induced surface charge density might reach levels of σ ~5.5 × 10 13 cm −2 , which leads to fields approaching 10 MV cm −1 in the AlN and at its interface with the GaN layers 20 . These enormous polarization-induced electric fields present in III-nitride heterostructures have been recently confirmed by direct measurement with nano-beam electron diffraction 26 . The induced field creates a depletion region within the UID collector spacer and an accumulation region in the UID emitter spacer.…”

Section: Resultsmentioning

confidence: 71%

Near-UV electroluminescence in unipolar-doped, bipolar-tunneling GaN/AlN heterostructures

et al. 2017

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Cross-gap light emission is reported in n-type unipolar GaN/AlN double-barrier heterostructure diodes at room temperature. Three different designs were grown on semi-insulating bulk GaN substrates using molecular beam epitaxy (MBE). All samples displayed a single electroluminescent spectral peak at 360 nm with full-width at half-maximum (FWHM) values no greater than 16 nm and an external quantum efficiency (EQE) of ≈0.0074% at 18.8 mA. In contrast to traditional GaN light emitters, p-type doping and p-contacts are completely avoided, and instead, holes are created in the GaN on the emitter side of the tunneling structure by direct interband (that is, Zener) tunneling from the valence band to the conduction band on the collector side. The Zener tunneling is enhanced by the high electric fields (~5 × 106 V cm−1) created by the notably large polarization-induced sheet charge at the interfaces between the AlN and GaN.

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“…Figure a shows the simulated intensity distribution at the diffraction plane, and thus at the segmented area detector, when a 300 kV electron probe passes 0.2 Å to the left of a gallium atomic column in a 1.6 nm thick GaN crystal oriented along the [112̅ 0] direction. GaN is a common material in a wide variety of optoelectronic devices, such as blue light-emitting diodes, and has been extensively studied using DPC-STEM at nanometer resolutions, exploring the possibility of detecting the piezoelectric fields in optoelectronic devices. − The probe intensity at the diffraction plane is shifted toward the Ga column due to the interaction between the incident electrons and the atomic electric field: the direction of deflection shows that the attractive force exerted on the incident electrons by the nucleus is dominant, although it is moderated by the screening electrons. The simulation exposes how the traditional picture of a rigid deflection of the probe due to the atomic electric field is only a simplification of the real effects, as described in recent experimental and theoretical , reports.…”

Section: Resultsmentioning

confidence: 99%

Probing the Internal Atomic Charge Density Distributions in Real Space

et al. 2018

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Probing the charge density distributions in materials at atomic scale remains an extremely demanding task, particularly in real space. However, recent advances in differential phase contrast-scanning transmission electron microscopy (DPC-STEM) bring this possibility closer by directly visualizing the atomic electric field. DPC-STEM at atomic resolutions measures how a sub-angstrom electron probe passing through a material is affected by the atomic electric field, the field between the nucleus and the surrounding electrons. Here, we perform a fully quantitative analysis which allows us to probe the charge density distributions inside atoms, including both the positive nuclear and the screening electronic charges, with subatomic resolution and in real space. By combining state-of-the-art DPC-STEM experiments with advanced electron scattering simulations we are able to map the spatial distribution of the electron cloud within individual atomic columns. This work constitutes a crucial step toward the direct atomic scale determination of the local charge redistributions and modulations taking place in materials systems.

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Direct Measurement of Polarization-Induced Fields in GaN/AlN by Nano-Beam Electron Diffraction

Cited by 26 publications

References 42 publications

Nonthermal Plasma Synthesis of Gallium Nitride Nanoparticles: Implications for Optical and Electronic Applications

Nonthermal Plasma Synthesis of Gallium Nitride Nanoparticles: Implications for Optical and Electronic Applications

Near-UV electroluminescence in unipolar-doped, bipolar-tunneling GaN/AlN heterostructures

Probing the Internal Atomic Charge Density Distributions in Real Space

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