Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography

Tang, Fengzai and Zhu, Tongtong and Oehler, Fabrice and Fu, Wai Yuen and Griffiths, James T. and Massabuau, Fabien C. -P. and Kappers, Menno J. and Martin, Tomas L. and Bagot, Paul A. J. and Moody, Michael P. and Oliver, Rachel A. (2015) Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography. Applied Physics Letters, 106 (7). 072104. ISSN 0003-6951

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Abstract

Atom probe tomography (APT) has been used to characterize the distribution of In atoms within non-polar a-plane InGaN quantum wells (QWs) grown on a GaN pseudo-substrate produced using epitaxial lateral overgrowth. Application of the focused ion beam microscope enabled APT needles to be prepared from the low defect density regions of the grown sample. A complementary analysis was also undertaken on QWs having comparable In contents grown on polar c-plane sample pseudo-substrates. Both frequency distribution and modified nearest neighbor analyses indicate a statistically non-randomized In distribution in the a-plane QWs, but a random distribution in the c-plane QWs. This work not only provides insights into the structure of non-polar a-plane QWs but also shows that APT is capable of detecting as-grown nanoscale clustering in InGaN and thus validates the reliability of earlier APT analyses of the In distribution in c-plane InGaN QWs which show no such clustering.

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