Relaxation of compressively strained AlInN on GaN


Epitaxial layers of wurtzite-phase Al1-xInxN, similar to 120 nm thick with (0 0 0 1) orientation, were grown by metal organic chemical vapour deposition on GaN buffer layers at setpoint temperatures between 760 and 840 degrees C. For growth temperatures >= 800 degrees C, the AlInN layers grew with uniform composition, pseudomorphic with the underlying GaN buffer layer. In the temperature range studied, the InN fractions are a linear function of the setpoint temperature and straddle the near-lattice-match composition around Al0.83In0.17N. Lowering the growth temperature to 760 degrees C caused a compositional grading, a marked change in surface morphology, and a reduction in AlInN crystal quality. The resulting AlInN layer consists of a compressively strained interfacial layer with a composition of Al0.76In0.24N and a mostly relaxed near-surface layer with a composition of A10.811no.19N. Atomic force microscopy suggests that a transition to a three-dimensional growth mode accompanies the structural relaxation and change in composition. (C) 2008 Elsevier B.V. All rights reserved.




Crystallography; Materials Science; Physics


Lorenz, K; Franco, N; Alves, E; Pereira, S; Watson, IM; Martin, RW; O'Donnell, KP

nossos autores


We acknowledge financial support by FCT Portugal (BPD/18958/2004 and PTDC/FIS/65233/2006). TEM analysis of sample S840 was provided by F.A. Ponce and Z.H. Wu, Arizona State University. We thank the referee for helpful comments.

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