Characterizing the thickness dependence of epitaxial GaN grown over GaN nanocolumns using X-ray diffraction

Shiao, Wen Yu; Tang, Tsung Yi; Chen, Yung Sheng; Averett, Kent L.; Albrecht, John D.; Yang, C. C.

doi:10.1016/j.jcrysgro.2008.04.006

Cited by 3 publications

(3 citation statements)

References 9 publications

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“…This shift in the GaN band-edge emission can be related to the release of tensile strain through the partially coalesced layer. This is in agreement with the observation by Shiao et al 17 where the strain across an overgrown GaN layer of similar thickness decreases with an increase in thickness of the coalescence layer. Similarly, Tang et al 11 observed a rebuilding of compressive strain (�0.66 GPa) in a GaN coa lesced layer over strain free nanocolumns grown on nanopat terned sapphire substrate.…”

Section: Resultssupporting

confidence: 93%

“…The merging of adja cent crystal domains, arising from non-perfectly aligned nano columns can account for the strain at the grain boundaries. 17 Figure 5(a) shows a secondary electron image of a crosssection, which was then mapped using CL hyperspectral imaging in the FESEM. The mapped area was 1 � 3 lm 2 with a step size of 100 nm and a dwell time of 500 ms per pixel.…”

Section: Resultsmentioning

confidence: 99%

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Cross-sectional and plan-view cathodoluminescence of GaN partially coalesced above a nanocolumn array

Lethy

Edwards

Liu

et al. 2012

Journal of Applied Physics

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The optical properties of GaN layers coalesced above an array of nanocolumns have important consequences for advanced optoelectronic devices. GaN nanocolumns coalesced using a nanoscale epitaxial overgrowth technique have been investigated by high resolution cathodoluminescence (CL) hyperspectral imaging. Plan-view microscopy reveals partially coalesced GaN layers with a sub-μm scale domain structure and distinct grain boundaries, which is mapped using CL spectroscopy showing high strain at the grain boundaries. Cross-sectional areas spanning the partially coalesced GaN and underlying nanocolumns are mapped using CL, revealing that the GaN bandedge peak shifts by about 25 meV across the partially coalesced layer of ∼2 μm thick. The GaN above the nanocolumns remains under tensile strain, probably due to Si out-diffusion from the mask or substrate. The cross-sectional data show how this strain is reduced towards the surface of the partially coalesced layer, possibly due to misalignment between adjacent partially coalesced regions

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Section: Resultssupporting

confidence: 93%

Section: Resultsmentioning

confidence: 99%

Cross-sectional and plan-view cathodoluminescence of GaN partially coalesced above a nanocolumn array

Lethy

Edwards

Liu

et al. 2012

Journal of Applied Physics

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“…First, we used a three-beam XRD technique for plotting the rocking curves in the ͑01-13͒/͑0-11-2͒ plane at various depths by changing the x-ray incident angle. [15][16][17][18] In such a measurement, depending on the incident angle of the x-ray beam, the XRD data mainly come from a certain depth of the sample. In the second depthdependent XRD method, a two-beam technique is used for calibrating the screw dislocation density, edge dislocation density, and the lateral domain size based on the equation 19…”

Section: Growth Conditions and Characterization Techniquesmentioning

confidence: 99%

Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy

Tang

Shiao

Cheng

et al. 2009

Journal of Applied Physics

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High-quality coalescence overgrowth of patterned-grown GaN nanocolumns on c-plane sapphire substrate with metal organic chemical vapor deposition is demonstrated. Although domain structures of a tens of micron scale in the overgrown layer can be identified with cathodoluminescence measurement, from atomic force microscopy ͑AFM͒ measurement, the surface roughness of the overgrown layer in an area of 5 ϫ 5 m 2 is as small as 0.411 nm, which is only one-half that of the high-quality GaN thin-film template directly grown on sapphire substrate ͑the control sample͒. Based on the AFM and depth-dependent x-ray diffraction measurements near the surface of the overgrown layer, the dislocation density is reduced to the order of 10 7 cm −2 , which is one order of magnitude lower than that of the control sample and two to three orders of magnitude lower than those of ordinary GaN templates for fabricating light-emitting diodes. Also, the lateral domain size, reaching a level of ϳ2.7 m, becomes three times larger than the control sample. Meanwhile, the ratio of photoluminescence intensity at room temperature over that at low temperature of the overgrown sample is at least six times higher than that of the control sample. Although the strain in nanocolumns is almost completely released, a stress of ϳ0.66 GPa is rebuilt when the coalescence overgrowth is implemented.

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Nitride Nanocolumns for the Development of Light-Emitting Diode

Tang

Lin

Chen

et al. 2010

IEEE Trans. Electron Devices

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Characterizing the thickness dependence of epitaxial GaN grown over GaN nanocolumns using X-ray diffraction

Cited by 3 publications

References 9 publications

Cross-sectional and plan-view cathodoluminescence of GaN partially coalesced above a nanocolumn array

Cross-sectional and plan-view cathodoluminescence of GaN partially coalesced above a nanocolumn array

Coalescence overgrowth of GaN nanocolumns on sapphire with patterned metal organic vapor phase epitaxy

Nitride Nanocolumns for the Development of Light-Emitting Diode

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