Spatial clustering of defect luminescence centers in Si-doped low resistivity Al0.82Ga0.18N

Kusch, Gunnar; Nouf-Allehiani, M.; Mehnke, Frank; Kühn, Christian; Edwards, P. R.; Wernicke, Tim; Knauer, A.; Kueller, V.; Naresh-Kumar, G.; Weyers, M.; Kneissl, Michael; Trager-Cowan, C.; Martin, Robert

doi:10.1063/1.4928667

Cited by 22 publications

(20 citation statements)

References 32 publications

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“…Detailed studies of dark spot characteristics in AlGaN are sparse and often restricted to the determination of their density. [ 2,4,10,17,24 ]…”

Section: Introductionmentioning

confidence: 99%

“…1) Surface states at the dislocation core and possibly point defects near the dislocation core act as centers for fast nonradiative recombination and form local sinks for charge carrier density. [ 5–10 ] The dark spots are formed by charge carrier diffusion to the carrier density sink and the resulting carrier density profile around threading dislocations. [ 1,7,11–13 ] 2) Strain fields around the dominating threading edge dislocations generate bandgap variations and piezoelectric fields near the semiconductor surface in GaN.…”

Section: Introductionmentioning

confidence: 99%

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Temperature Dependence of Dark Spot Diameters in GaN and AlGaN

Netzel

Knauer

Brunner

et al. 2021

Physica Status Solidi (b)

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Threading dislocations in c‐plane (Al,Ga)N layers are surrounded by areas with reduced light generation efficiency, called “dark spots.” These areas are observable in luminescence measurements with spatial resolution in the submicrometer range. Dark spots reduce the internal quantum efficiency in single layers and light‐emitting devices. In cathodoluminescence measurements, the diameter of dark spots (full width at half maximum [FWHM]) is observed to be 200–250 nm for GaN. It decreases by 30–60% for AlxGa1−xN with x ≈ 0.5. Furthermore, the dark spot diameter increases with increasing temperature from 83 to 300 K in AlGaN, whereas it decreases in GaN. Emission energy mappings around dark spots become less smooth and show sharper features on submicrometer scales at low temperature for AlGaN and, on the contrary, at high temperature for GaN. It is concluded that charge carrier localization dominates the temperature dependence of dark spot diameters and of the emission energy distribution around threading dislocations in AlGaN, whereas the temperature‐dependent excitation volume in cathodoluminescence and charge carrier diffusion limited by phonon scattering are the dominant effects in GaN. Consequently, with increasing temperature, nonradiative recombination related to threading dislocations extends to wider regions in AlGaN, whereas it becomes spatially limited in GaN.

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“…Detailed studies of dark spot characteristics in AlGaN are sparse and often restricted to the determination of their density. [ 2,4,10,17,24 ]…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Temperature Dependence of Dark Spot Diameters in GaN and AlGaN

Netzel

Knauer

Brunner

et al. 2021

Physica Status Solidi (b)

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“…We recently demonstrated the growth of highly conductive bulk Al 0.8 Ga 0.2 N:Si layers with very low resistivities of 0.026 Ω cm . However, these bulk AlGaN layers exhibit relatively rough surface morphologies with up to 30 nm high spiral hillocks, correlated with threading dislocations with a screw component . Additionally, Al x Ga 1−x N:Si layers with an average composition of x ≤ 0.8 can exhibit notable compositional fluctuation and partial strain relaxation, which are detrimental to the growth of smooth and homogeneous quantum wells.…”

Section: Introductionmentioning

confidence: 99%

MOVPE Growth of Smooth and Homogeneous Al_0.8Ga_0.2N:Si Superlattices as UVC Laser Cladding Layers

Kühn

Simoneit

Martens

et al. 2018

Physica Status Solidi (a)

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Smooth, uniform, and conductive Al x Ga 1Àx N layers with high aluminum mole fractions of x > 0.7 are required as cladding layers for laser diodes emitting in the deep ultraviolet spectral region. In this paper, the growth of silicon-doped AlGaN/AlGaN superlattices by metal-organic vapor phase epitaxy is investigated and compared to bulk AlGaN layers. It is found that the superlattice approach enables the growth of AlGaN layers with improved lateral uniformity of composition and strain state. In order to reduce the surface roughness, growth interruptions between the superlattice layers are investigated. With increasing growth interruption time, the average aluminum content is increasing and the superlattice period thickness is decreasing. Scanning transmission electron microscopy investigations show that the growth interruptions lead to more abrupt interfaces and to the formation of one to two monolayer thin aluminum-rich AlGaN layers at each interface. This also leads to a significantly smoother surface morphology. Low resistivities of 0.025 Ω cm are obtained for AlGaN:Si superlattices with average aluminum content of x ¼ 0.8. The influence of the surface morphology of the AlGaN cladding layers on optically pumped laser heterostructures is investigated. By using a smooth AlGaN superlattice, the lasing threshold decreases by a factor of 2 compared to lasers with bulk AlGaN cladding layers.

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“…The TDD of the ELO AlN/sapphire is 1:5 Â 10 9 cm À2 . 13,14 The layer structure consists of a 400 nm thick AlN buffer layer, a 25 nm thick AlN to Al 0.90 Ga 0.10 N graded transition layer, 100 nm undoped Al 0.90 Ga 0.10 N, and 980 nm to 1400 nm Sidoped Al 0.90 Ga 0.10 N. 15 The composition of the samples was determined under consideration of the layer strain state by high resolution x-ray diffractometry (HR-XRD) measuring reciprocal space maps near the (10-15) AlN reflex. 16,17 The resistivity of the samples was determined by contactless (eddy current) resistivity measurements in a Delcom system.…”

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confidence: 99%