Carrier Diffusion in 
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: A Cathodoluminescence Study. III. Nature of Nonradiative Recombination at Threading Dislocations

Lähnemann, Jonas; Kaganer, Vladimir M.; Sabelfeld, Karl K.; Kireeva, A. E.; Jahn, U.; Chèze, Caroline; Calarco, Raffaella; Brandt, O.

doi:10.1103/physrevapplied.17.024019

Cited by 17 publications

(8 citation statements)

References 56 publications

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“…This allows us to investigate the impact of non-radiative PD density on carrier diffusion, which was recently highlighted as an area where studies are lacking. 46 At 10 K carriers in InGaN/GaN QWs have near-zero diffusivity, and therefore negligible diffusion lengths. As the temperature is raised, the diffusion constant increases before saturating at ∼ 200 K. 28 The resulting increase in diffusion length reduces the spatial resolution at higher temperatures, as shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The importance of using CL emission energy rather than intensity for diffusion analysis has been emphasised for the case of threading dislocations in GaN. 46 Since we are not interested in macroscopic changes in the peak energy with temperature, we subtract the mean peak energy from each image to map deviation from average peak energy, ∆E. These images then reflect inhomogeneity across the QW.…”

Section: Resultsmentioning

confidence: 99%

“…S2a, we can see that the vast majority of the excitation energy (95 %) is absorbed in the top 20 nm of the sample, hence the InGaN/GaN single QW is placed only 15 nm below the surface. This design ensures all generated carriers are able to reach the QW in the entire temperature range we explore, since the carrier diffusion length in GaN is always above 15 nm from 10 K up to 300 K. 46,55,56 In addition, using thin top layers limits any lateral carrier spreading that can occur before the carriers relax to the QW. The radial FWHM of the interaction volume in Fig.…”

Section: Carrier Injection In Cathodoluminescencementioning

confidence: 99%

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Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

et al. 2021

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Crystallographic point defects (PDs) can dramatically decrease the efficiency of optoelectronic semiconductor devices, many of which are based on quantum well (QW) heterostructures. However, spatially resolving individual nonradiative PDs buried in such QWs has so far not been demonstrated. Here, using high-resolution cathodoluminescence (CL) and a specific sample design, we spatially resolve, image, and analyze nonradiative PDs in InGaN/GaN QWs at the nanoscale. We identify two different types of PDs by their contrasting behavior with temperature and measure their densities from 10 14 cm −3 to as high as 10 16 cm −3 . Our CL images clearly illustrate the interplay between PDs and carrier dynamics in the well: increasing PD concentration severely limits carrier diffusion lengths, while a higher carrier density suppresses the nonradiative behavior of PDs. The results in this study are readily interpreted directly from CL images and represent a significant advancement in nanoscale PD analysis.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Carrier Injection In Cathodoluminescencementioning

confidence: 99%

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Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

et al. 2021

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“…In other words, the QW emission is produced exclusively by direct carrier generation within the QW structure, while thermalized carriers in the GaN or GaAs matrix cannot contribute to it. These results will be used in two subsequent studies of the temperature-dependent carrier diffusion in GaN presented in the companion papers CD2 [23] and CD3 [24].…”

Section: Introductionmentioning

confidence: 99%

“…In particular, we attribute the broadening to the suppression of electron-phonon scattering processes with decreasing temperature, and its dependence on acceleration voltage to the slow-down of carrier cooling due to hot phonons. Finally, we present a phenomenological model reproducing the experimental profiles with a single free parameter that we employ to determine the diffusion length in the following papers CD2 [23] and CD3 [24].…”

Section: Introductionmentioning

confidence: 99%

Carrier diffusion in GaN -- a cathodoluminescence study. I: Temperature-dependent generation volume

Jahn,

Kaganer,

Sabelfeld

et al. 2020

Preprint

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The determination of the carrier diffusion length of semiconductors such as GaN and GaAs by cathodoluminescence imaging requires accurate knowledge about the spatial distribution of generated carriers. To obtain the lateral distribution of generated carriers for sample temperatures between 10 and 300 K, we utilize cathodoluminescence intensity profiles measured across single quantum wells embedded in thick GaN and GaAs layers. Thin (Al,Ga)N and (Al,Ga)As barriers, respectively, prevent carriers diffusing in the GaN and GaAs layers to reach the well, which would broaden the profiles. The experimental CL profiles are found to be systematically wider than the energy loss distributions calculated by means of the Monte Carlo program CASINO, with the width monotonically increasing with decreasing temperature. This effect is observed for both GaN and GaAs and becomes more pronounced for higher acceleration voltages. We discuss this phenomenon in terms of the electron-phonon interaction controlling the energy relaxation of hot carriers, and of the non-equilibrium phonon population created by this relaxation process. Finally, we present a phenomenological approach to simulate the carrier generation volume that can be used for the investigation of the temperature dependence of carrier diffusion.

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Active Ferromagnetic Metasurface with Topologically Protected Spin Texture for Spectral Filters

Chen

Cros

et al. 2022

Adv Funct Materials

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Electromagnetic metasurfaces modulate a material's response to electromagnetic waves by specifically arranged elements with dimensions below the wavelength. They have opened new fields of research, including flat optics and nanophotonics on a chip. Ferromagnetic metasurfaces could become the building blocks for manipulation of both microwaves and spin waves (magnons). So far, the functionality of magnonic devices has been limited by high intrinsic damping of the materials employed, suppressing long‐distance spin‐wave propagation. Here ferromagnetic metasurfaces are reported, which are created from periodic arrays of either 15 nm thick Co20Fe60B20, Ni80Fe20 or Co nanodisks on ferrimagnetic yttrium iron garnet (YIG) hosting topologically protected vortex states. This device, a reconfigurable spectral filter, operates in the microwave regime near 0.9 GHz and manipulates long‐distance spin‐wave transmission in thin YIG. An efficiency of 98.5% is demonstrated, with the metasurface covering only 15% of the microwave antenna. This first demonstration of a ferromagnetic metasurface opens unprecedented possibilities for on‐chip control of microwaves in low‐damping ferrimagnetic insulators.

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Carrier Diffusion in GaN : A Cathodoluminescence Study. III. Nature of Nonradiative Recombination at Threading Dislocations

Cited by 17 publications

References 56 publications

Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

Imaging Nonradiative Point Defects Buried in Quantum Wells Using Cathodoluminescence

Carrier diffusion in GaN -- a cathodoluminescence study. I: Temperature-dependent generation volume

Active Ferromagnetic Metasurface with Topologically Protected Spin Texture for Spectral Filters

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