Papers by Keyword: Critical Thickness

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Authors: Md. Arafat Hossain, Md. Rafiqul Islam
Abstract: This paper presents a theoretical calculation of misfit dislocation and strain relaxation in compositionally step graded InxGa 1-x N grown on GaN using the total dislocation energy at each interface. The results also compared with uniform layer of In 0.17 Ga 0.83 N and In 0.14 Ga 0.86 N grown differently on GaN. Due to having residual strain and a step increase in indium composition a lower misfit strain in upper layers and hence larger critical thickness at each interface has been reported. These effects significantly reduced the misfit dislocations from 2.6×105 cm-1 to 9.5×104 cm-1 in step graded In 0.14 Ga 0.86 N(500nm)/In 0.09 Ga 0.91 N(100nm)/In 0.05 Ga 0.95 N(100nm)/GaN layers instead of a uniform In 0.14 Ga 0.86 N(700nm)/GaN. A small residual strain of 0.0007 after 700 nm graded layer thickness has been reported with 87.04% strain relaxation.
Authors: D. Holec, Colin J. Humphreys
Abstract: We investigate critical thicknesses of InGaN epilayers grown on GaN substrates with the growth-plane not being the c-plane. In particular, we focus on non-polar orientations with growth planes being the m- and a-planes. We have taken into account the proper hexagonal symmetry of wurtzite GaN. We have found that there is only a small difference in the critical thickness for the cplane and the a-plane material; however, in the case of the m-plane material, we predict a quite different behaviour along the (in-plane) c-axis and the perpendicular (in-plane) a-direction.
Authors: D. Reisinger, M.J. Kastner, K. Wolf, H. Steinkirchner, W. Häckl, H. Stanzl, W. Gebhardt
Authors: U. Herr, H. Geisler, Konrad Samwer
Authors: M.A. Vidal, M.E. Constantino, B. Salazar-Hernández, H. Navarro-Contreras, M. López-López, I. Hernández-Calderón, Hiroo Yonezu
Authors: A. Fischer, G. Kissinger, Hans Richter, P. Zaumseil
Authors: Arun Kumar, Anandh Subramaniam
Abstract: During the growth of an epitaxial overlayer on a thick substrate (GeSi on Si), an interfacial misfit dislocation becomes energetically favourable on exceeding the critical thickness. In substrates of finite thickness, the value of critical thickness is altered with respect to thick substrates. Thin substrates can bend and partially relax the coherency stresses, thus contributing to the altered value of the critical thickness. The current work aims at simulating the stress state of a growing finite epitaxial overlayer on a substrate of finite thickness, using finite element method. The numerical model is used to calculate the critical thickness for substrates with finite thickness. Eigenstrains will be imposed in selected regions in the domain towards this end. Size of the substrate for which it is not energetically favourable to accommodate a misfit dislocation is determined from the simulations (i.e. the system remains coherent for substrates below this thickness). Important effects arising in the transition regime of substrate thicknesses are also investigated.
Authors: Anisul Islam, Durjoy Dev, Md. Arafat Hossain, Md. Rafiqul Islam, A. Yamamoto
Abstract: The performances of heterostructural devices are often limited by misfit dislocation. In this paper, a theoretical approach for misfit dislocation reduction of wurtzite InxGa1-xN/GaN is presented. The linear and exponential grading techniques have been modeled for the reduction of dislocation. An energy balance model has been taken into consideration and modified for wurtzite structure to evaluate the misfit dislocation density. The value of misfit dislocation has been reduced from 7.112×1010 cm-2 to 6.19×106 cm-2 and 7.039×1010 cm-2 to 6.121×106 cm-2 at the plane 1/3<> {} and 1/3<>{} respectively for linear grading. In case of exponential grading the dislocation density has been reduced to 2.762×105 cm-2 for both slip systems. Because of tapered grading coefficient a tapered dislocation profile has been reported in case of exponential grading technique. Finally, a comparative study has been shown among without graded, linear and exponential grading.
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