Investigation of nanoscale composition fluctuations in InGaN using optical transmission spectroscopy and near-field scanning optical microscopy
ABSTRACT Nanoscale composition fluctuations in InGaN alloy epitaxial layers have been investigated by optical transmission spectroscopy and near-field scanning optical microscopy. A spatial variation of the optical transmission at 488 nm is observed, which is attributed to an inhomogeneous indium distribution. Both the characteristic wavelength and the normalized root mean square magnitude of the compositional fluctuations increase with increasing In concentration. The fluctuations are well described in terms of a spinodal decomposition model.
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ABSTRACT: This paper proposes for the first time the preparation of n-InGaN/p-Si templates as substrates for InGaN device applications. By using MOVPE, a thick (~0.5 m) InGaN with an intermediate In composition has been successfully grown on Si(111) substrates using an AlN interlayer. By optimizing growth temperature and TMI/(TMI+TEG) molar ratio, InGaN films with In content up to 0.5 are successfully grown. Tensile stress in InGaN films grown at 700°C is estimated to be about half of that for GaN grown at 1100°C and no cracks are found in the InGaN layers. The films grown at a relatively high temperature (700-750°C) show phase separation when their thickness exceeds a critical value. Critical thickness for phase separation is larger for a film grown at a lower temperature with a high In content. For InGaN grown at 600°C with a thickness of 0.8 m, no phase separation is detected by both X-ray diffraction and PL. Such a low temperature-grown InGaN shows a large tilt fluctuation. Ohmic I-V characteristics are obtained between n-InGaN and p-Si and the resistance is markedly decreased with increasing In content in InGaN. The Si pn junction beneath the In0.42Ga0.58N layer behaves well as a solar cell with an InGaN filter. For both n-InGaN/p-Si, the presence of an AlN interlayer between the epilayer and the substrate does not have a significant contribution to the series resistance.Proceedings of SPIE - The International Society for Optical Engineering 03/2013; DOI:10.1117/12.999272 · 0.20 Impact Factor
physica status solidi (b) 05/2011; 248:1270-1274. DOI:10.1002/pssb.201046108 · 1.61 Impact Factor
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ABSTRACT: The spatial distribution features of indium composition in In0.17Al0.83N epilayers have been investigated by means of cathodoluminescence and photoluminescence. It is demonstrated that there is excellent compositional homogeneity in In0.17Al0.83N, implying there is almost no phase separation that would cause compositional inhomogeneity. This result is quite different from the case in InxGa1-xN alloys. Based on the analysis of the temperature--mole fraction (T--x) phase diagram, we believe that the In0.17Al0.83N alloy is metastable against local decomposition. The high kinetic energy barrier caused by the considerable covalent bond mismatch between Al--N and In--N is supposed to account for the realization of such a metastable state.Applied Physics Express 10/2012; 5(10):1002-. DOI:10.1143/APEX.5.101002 · 2.57 Impact Factor