X-ray diffraction analysis and scanning micro-Raman spectroscopy of structural irregularities and strains deep inside the multilayered InGaN/GaN heterostructure |
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Authors: | V V Strelchuk V P Kladko E A Avramenko O F Kolomys N V Safryuk R V Konakova B S Yavich M Ya Valakh V F Machulin A E Belyaev |
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Affiliation: | 1.Lashkaryov Institute of Semiconductor Physics,National Academy of Sciences of Ukraine,Kyiv,Ukraine;2.ZAO Svetlana-Optoelectronics,St. Petersburg,Russia |
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Abstract: | High-resolution X-ray diffraction analysis and scanning confocal Raman spectroscopy are used to study the spatial distribution
of strains in the In
x
Ga1 − x
N/GaN layers and structural quality of these layers in a multilayered light-emitting diode structure produced by metal-organic
chemical vapor deposition onto (0001)-oriented sapphire substrates. It is shown that elastic strains almost completely relax
at the heterointerface between the thick GaN buffer layer and In
x
Ga1 − x
N/GaN buffer superlattice. It is established that the GaN layers in the superlattice are in a stretched state, whereas the
alloy layers are in a compressed state. In magnitude, the stretching strains in the GaN layers are lower than the compressive
strains in the InGaN layers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a
smaller number of dislocations and the distribution of dislocations is more randomly disordered. In micro-Raman studies on
scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric gradient distributions
of strains and crystal imperfections of the epitaxial nitride layers along the direction of growth. It is shown that the emission
intensity of the In
x
Ga1 − x
N quantum well is considerably (more than 30 times) higher than the emission intensity of the GaN barrier layers, suggesting
the high efficiency of trapping of charge carriers by the quantum well. |
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Keywords: | |
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