Accession Number : ADA337316
Title : Deposition of Gallium Nitride Epilayers by OMVPE
Descriptive Note : Final rept. 30 Jun 94-29 Jun 97
Corporate Author : CARNEGIE-MELLON UNIV PITTSBURGH PA DEPT OF MATERIALS SCIENCE AND ENGINEERING
Personal Author(s) : Skowronski, M.
PDF Url : ADA337316
Report Date : 14 JAN 1998
Pagination or Media Count : 11
Abstract : Gallium nitride films have been deposited on sapphire substrates by organometallic vapor phase epitaxy and their structural quality assessed by Transmission Electron Microscopy and high resolution x-ray diffraction. The dominant type of threading dislocation was determined to be pure edge with Burgers vector 1/3 <11.0>. Dislocations are arranged into arrays corresponding to low angle twist grain boundaries with typical in-basal-plane misorientations of about 1 degree. The granular structure of the GaN film originates at the nucleation growth phase within low temperature GaN buffer. A new figure of merit for structural quality of nitride films (phi scan value) was proposed in order to track the amount of twist. New defects characteristic of GaN and AlGaN films have been observed and reported for the first time. These are nano-pipes or nano-tubes, empty cylinders with diameters of approximately 10 nanometers propagating along the c-axis. Nano-tubes penetrate the entire film thickness and terminate in the facetted surface crater. Their density correlates with oxygen and silicon concentration in the film and can exceed 10(exp5)/cm2 in AlGaN.
Descriptors : *EPITAXIAL GROWTH, *GALLIUM NITRIDES, MORPHOLOGY, THIN FILMS, X RAY DIFFRACTION, SUBSTRATES, HIGH RESOLUTION, VAPOR PHASES, ELECTRON MICROSCOPY, SAPPHIRE, DISLOCATIONS, SURFACE PROPERTIES.
Subject Categories : Crystallography
Distribution Statement : APPROVED FOR PUBLIC RELEASE