Characterization of MOVPE-grown (Al, In, Ga) N heterostructures by quantitative analytical electron microscopy |
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Authors: | H Lakner G Brockt C Mendorf A Radefeld F Scholz V Härle J Off A Sohmer |
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Affiliation: | 1. Werkstoffe der Elekrotechnik, Universit?t Duisburg, 47048, Duisburg, Germany 2. 4 Physikalisches Institut, Universit?t Stuttgart, 70550, Stuttgart, Germany
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Abstract: | The low pressure metalorganic vapor phase epitaxy growth of wurzite (Al, In, Ga)N heterostructures on sapphire substrates
is investigated by quantitative analytical scanning transmission electron microscopy techniques like atomic number (Z-) contrast
imaging and convergent beam electron diffraction (CBED). Especially (In, Ga)N quantum wells of different thicknesses as well
as superlattices were analyzed with respect to defects, chemical composition variations, interface abruptness and strain (relaxation)
effects. The interfaces in In0.12Ga0.88N/GaN quantum wells appear to be asymmetric. Additionally, we found composition variations of ΔxIn≥0.03 within the InGaN quantum wells. The application of electron diffraction techniques (CBED) yields quantitative information
on strain and relaxation effects. For the case of 17 nm thick InGaN quantum wells, we observed relaxation effects which are
not present in the investigated thin quantum wells of 2 nm thickness. The experimentally obtained diffraction patterns were
compared to simulations in order to get values for strain within the quantum wells. Additionally, the influence of dislocations
on the digression of superlattices is investigated. |
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Keywords: | Convergent beam electron diffractdion (CBED) InGaN quantum wells STEM Z-contrast |
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