Determination of strain state and composition of highly mismatched group-III nitride heterostructures by x-ray diffraction

Brandt, O.; Waltereit, Patrick

doi:10.1088/0022-3727/35/7/301

Cited by 95 publications

(65 citation statements)

References 37 publications

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“…In order to confirm this assignment a simulation using the kinematic scattering is also shown in Fig. 2 (lower full curve) [6]. The widths used in the calculation are 5 nm for the GaN well and 10 nm for the Al 0.25 Ga 0.75 N barrier, which is in excellent agreement with the targeted growth values.…”

supporting

confidence: 66%

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Köhler

Potthast

et al. 2002

phys. stat. sol. (c)

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The structural and optical properties of cubic Al 0.25 Ga 0.75 N/GaN multi quantum well structures grown on GaAs (001) substrates by radio-frequency plasma-assisted molecular beam epitaxy (MBE) are reported. Transmission electron microscopy (TEM), high resolution X-ray diffraction (HRXRD), and cathodoluminescence (CL) measurements are used to characterize the cubic Al 0.25 Ga 0.75 N/GaN quantum wells. The interfaces between the quantum-well and barrier layers are well resolved, abrupt and the entire structure shows an excellent periodicity. Due to the high dislocation density of about 10 10 cm -2 a severe broadening of the XRD-reflection is observed and superlattice satellite peaks are only weakly indicated. Further, a wavy structure is seen in TEM at the coalescence of submicron-size grains. Nevertheless, CL at room temperature shows a strong emission of quantized states at 3.352 eV.

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supporting

confidence: 66%

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Köhler

Potthast

et al. 2002

phys. stat. sol. (c)

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“…Using the known sapphire lattice constants, a = 4.7588 Å and c = 12.992 Å, the in-plane ͑a͒ and out-of-plane ͑c͒ hexagonal cell dimensions of the AlGaN layers were calculated from their respective values of and measured on the RSMs, allowing us to independently determine the Al composition and strain state of the films by using standard x-ray analysis. The degree of relaxation R =1−͑ meas / coh ͒ was used as a measure of the strain state of the epilayer, 16 where coh is the elastic strain in the fully coherent epitaxial layer ͑ coh is equal in magnitude to the crystal mismatch m between the AlGaN layers͒ and meas was the elastic strain value determined from the RSM analysis of the upper epilayer. The strain determined from the XRD data, meas , was the elastic strain affecting the layer, and it was given by meas = coh − pl , where pl stands for the relaxed strain due to plastic deformation.…”

Section: Resultsmentioning

confidence: 99%

Role of inclined threading dislocations in stress relaxation in mismatched layers

Cantu

Waltereit

et al. 2005

Journal of Applied Physics

122

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͑0001͒-oriented epitaxial wurtzite III-nitride layers grown on mismatched substrates have no resolved shear stress on the natural basal and prismatic slip planes; however, strained III-nitride layers may gradually relax. We report on the stress relaxation of Al 0.49 Ga 0.51 N layers grown on nominally relaxed Al 0.62 Ga 0.38 N buffer layers on sapphire. The reduction in elastic strain of the Al 0.49 Ga 0.51 N was enhanced by Si doping which caused an increased surface roughness. Despite the Si doping, the films always sustained step-flow growth. The extent of relaxation of the Al 0.49 Ga 0.51 N layer was determined by on-axis -2 scans of ͑000l͒ peaks and reciprocal space maps of inclined ͑off-axis͒ peaks. Cross-section and plan-view transmission electron microscopy studies showed that the threading dislocations in the Al 0.49 Ga 0.51 N layer inclined from the ͓0001͔ direction towards ͗1100͘ directions by ϳ15-25°, perpendicular to their Burgers vector ͑ 1 3 ͗1120͘ ͒ . These inclined threading dislocations have a misfit dislocation component and thus provide stress relief. The contribution of the dislocation inclination to the degree of relaxation has been formulated and the energy release has been determined for dislocation inclination in mismatched stressed layers.

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“…The experimental results were simulated using the dynamical x-ray diffraction model reported in Ref. 22.…”

Section: Experiments and Methodsmentioning

confidence: 99%

Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/In
Fernández-Garrido
¹
,
Lähnemann
²
,
Hauswald
³

et al. 2016
Phys. Rev. Applied
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14
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We investigate the luminescence of Ga-and N-polar In x Ga 1−x N/In y Ga 1−y N quantum wells grown by plasma-assisted molecular beam epitaxy on freestanding GaN as well as 6H-SiC substrates. In striking contrast to their Ga-polar counterparts, the N-polar quantum wells prepared on freestanding GaN do not exhibit any detectable photoluminescence even at 10 K. Theoretical simulations of the band profiles combined with resonant excitation of the quantum wells allow us to rule out carrier escape and subsequent surface recombination as the reason for this absence of luminescence. To explore the hypothesis of a high concentration of nonradiative defects at the interfaces between wells and barriers, we analyze the photoluminescence of Ga-and N-polar quantum wells prepared on 6H-SiC as a function of the well width. Intense luminescence is observed for both Ga-and N polar samples. As expected, the luminescence of the Ga-polar quantum wells quenches and red-shifts with increasing well width due to the quantum confined Stark effect. In contrast, both the intensity and the energy of the luminescence from the N-polar samples are essentially independent of well width. Transmission electron microscopy reveals that the N-polar quantum wells exhibit abrupt interfaces and homogeneous composition, excluding emission from In-rich clusters as the reason for this anomalous behavior. The microscopic origin of the luminescence in the N-polar samples is elucidated using spatially resolved cathodoluminescence spectroscopy. Regardless of well width, the luminescence is found to not originate from the N-polar quantum wells, but from the semipolar facets of ∨-pit defects. These results cast serious doubts on the potential of N-polar In x Ga 1−x N/In y Ga 1−y N quantum wells grown by plasma-assisted molecular beam epitaxy for the development of long-wavelength light emitting diodes. What remains to be seen is whether unconventional growth conditions may enable a significant reduction in the concentration of nonradiative defects.

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Determination of strain state and composition of highly mismatched group-III nitride heterostructures by x-ray diffraction

Cited by 95 publications

References 37 publications

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Role of inclined threading dislocations in stress relaxation in mismatched layers

Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/In
Fernández-Garrido
¹
,
Lähnemann
²
,
Hauswald
³

et al. 2016
Phys. Rev. Applied
Self Cite
17
1
14
0
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Determination of strain state and composition of highly mismatched group-III nitride heterostructures by x-ray diffraction

Cited by 95 publications

References 37 publications

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Cathodoluminescence, High‐Resolution X‐Ray Diffraction and Transmission‐Electron‐Microscopy Investigations of Cubic AlGaN/GaN Quantum Wells

Role of inclined threading dislocations in stress relaxation in mismatched layers

Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/InFernández-Garrido1, Lähnemann2, Hauswald3 et al. 2016Phys. Rev. AppliedSelf Cite171140View full textAdd to dashboardCite

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Comparison of the Luminous Efficiencies of Ga- and N-PolarInxGa1−xN/In
Fernández-Garrido
¹
,
Lähnemann
²
,
Hauswald
³

et al. 2016
Phys. Rev. Applied
Self Cite
17
1
14
0
View full text Add to dashboard Cite