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Microstructure and strength of AlN–SiC interface studied by synchrotron X-rays
Argunova, T. S.,Gutkin, M. Y.,Shcherbachev, K. D.,Je, J. H.,Lim, J. H.,Kazarova, O. P.,Mokhov, E. N. Springer Science + Business Media 2017 JOURNAL OF MATERIALS SCIENCE - Vol.52 No.8
<P>Bulk AlN crystals grown by sublimation on SiC substrates exhibit relatively high dislocation densities. The kind of defect formation at early growth stages influences the structural quality of the grown crystals. In this work, the dislocation distribution near to the interface is understood through investigation of thin (<= 1.5 mm) continuous (non-cracked) freestanding crystals obtained in one process with the evaporation of the substrates. TheAlN specimens were characterized using synchrotron radiation imaging techniques. We revealed by triple-axis X-ray diffraction study that, near to the former interface, randomly distributed dislocations configured to form boundaries between similar to 0.02 degrees misoriented sub-grains (from [0001] direction). Threading dislocation structure similar to that in epitaxial GaN films was not detected. To explain these observations, a theoretical model of misfit stress relaxation near the interface is suggested.</P>
Polyakov, A. Y.,Cho, Han-Su,Yun, Jin-Hyeon,Lee, In-Hwan,Yakimov, E. B.,Smirnov, N. B.,Shcherbachev, K. D. The Electrochemical Society 2016 ECS journal of solid state science and technology Vol.5 No.6
<P>GaN/InGaN multiple quantum well (MQW) structures with undoped n-GaN cap imitating true light emitting diodes were grown on sapphire and converted to deep nanopillar (NP) structures by dry etching beyond the MQW region. Structural measurements, electrical measurements on Schottky diodes, microcathodoluminescence (MCL) spectra measurements indicate a strong relaxation of strain in NP MQWs manifested in the prominent increase of the bowing radius of the structures and in the blueshift of the MQW peak in MCL spectra. Various treatments of the as-etched NP MQWs (annealing at 700 degrees C, etching in KOH, and soaking in (NH4)(2)S) progressively decreased the leakage current of Schottky diodes and increased the MQW MCL peak intensity due to the suppression of the dry-etching damage of the nanopillar sidewalls. (C) 2016 The Electrochemical Society. All rights reserved.</P>