Transmission electron microscopy study of defect reduction in two-step lateral epitaxial overgrown nonplanar GaN substrate templates
نویسندگان
چکیده
Transmission electron microscopy (TEM) is carried out to characterize the extended defect reduction in low-defect nonplanar GaN substrate templates grown by lateral epitaxial overgrowth (LEO). The LEO nonplanar GaN substrate template has a trapezoidal cross section with smooth (0 0 0 1) and f1 1 2̄ 2g facets. We demonstrate here the dislocation distribution and behavior in both ordinary LEO and two-step LEO. Penetration of threading dislocations (TDs) beyond mask windows is observed in ordinary LEO substrates. In twostep LEO substrates, which utilize the tendency for TDs to bend 901 at certain plane interfaces, only a type dislocations with Burgers vector b 1⁄4 1 3 h1 1 2̄ 0i are generated in the upper part above the TD bending zone between two mask windows with a density of 8 10 cm , and there are almost no dislocations in the LEO wing region. This approach provides a promising path to produce lowdefect GaN substrate templates for high-performance buried heterostructure lasers. r 2006 Elsevier B.V. All rights reserved. PACS: 68.55. a; 61.72.Lk; 81.05.Ea; 61.72.Ff; 68.37. d; 81.15.Gh; 68.37.Lp
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