The Structural Quality Of Al_xga_(1-x)n Epitaxial Layers Grown By Digitally Alloyed Modulated Precursor Epitaxy Determined By Transmission Electron Microscopy

摘要

Al_xGa_(1-x)N layers of varying composition (0.5 < x_(Al) < 1.0) grown in the digitally alloyed modulated precursor epitaxial regime employing AlN and GaN binary sublayers by metal organic chemical vapor deposition on AlN templates were characterized by transmission electron microscopy techniques. Fine lamellae were observed in bright field images that indicate a possible variation in composition due to the modulated nature of growth. In higher Ga content samples (x_(Al) < 0.75), a compositional inhomogeneity associated with thicker island regions was observed, which is determined to be due to large Ga-rich areas formed at the base of the layer. Possible causes for the separation of Ga-rich material are discussed in the context of the growth regime used.