The Structural Quality of AlxGa1-xN Epitaxial Layers Grown by Digitally-AlloyedModulated Precursor Epitaxy Determined by Transmission Electron Microscopy

Al(x)Ga(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 sub-layers by metalorganic 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 inhomogeniety 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

The Structural Quality of AlxGa1-xN Epitaxial Layers Grown by Digitally-Alloyed Modulated Precursor Epitaxy Determined by Transmission Electron Microscopy

Al(x)Ga(1-x)N layers of varying composition (0.

The Structural Quality of AlxGa1-xN Epitaxial Layers Grown by Digitally-Alloyed Modulated Precursor Epitaxy Determined by Transmission Electron Microscopy

Al(x)Ga(1-x)N layers of varying composition (0.

Erratic Dislocations within Funnel Defects in AlN Templates for AlGaN Epitaxial Layer Growth

We report our transmission electron microscopy observations of erratic dislocation behavior within funnel-like defects in the top of AlN templates filled with AlGaN from an overlying epitaxial layer. This dislocation behavior is observed in material where phase separation is also observed. Several bare AlN templates were examined to determine the formation mechanism of the funnels. Our results suggest that they are formed prior to epitaxial layer deposition due to the presence of impurities during template re-growth. We discuss the erratic dislocation behavior in relation to the presence of the phase-separated material and the possible effects of these defects on the optoelectronic properties

Molecular beam epitaxial growth of Bi2Te3 and Sb2Te3 topological insulators on GaAs (111) substrates: a potential route to fabricate topological insulator p-n junction

High quality Bi2Te3 and Sb2Te3 topological insulators films were epitaxially grown on GaAs (111) substrate using solid source molecular beam epitaxy. Their growth and behavior on both vicinal and non-vicinal GaAs (111) substrates were investigated by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and high resolution transmission electron microscopy. It is found that non-vicinal GaAs (111) substrate is better than a vicinal substrate to provide high quality Bi2Te3 and Sb2Te3 films. Hall and magnetoresistance measurements indicate that p type Sb2Te3 and n type Bi2Te3 topological insulator films can be directly grown on a GaAs (111) substrate, which may pave a way to fabricate topological insulator p-n junction on the same substrate, compatible with the fabrication process of present semiconductor optoelectronic devices