Characterization of oxide precipitates in epitaxial InN by transmission electron microscopy

InN thin films have been grown epitaxially on GaN-buffered sapphire substrates by molecular-beam epitaxy at 500 °C. A high level of oxygen contamination in the growth chamber led to formation of In₂O₃ precipitates in the films. These precipitates were characterized in detail by transmission electron microscopy (TEM). The concentration of In₂O₃ was estimated to be less than 0.07 vol % in the present samples of oxygen content ∼0.5 at. %. Cross-sectional TEM investigations revealed that the precipitates adopt a preferred crystallographic orientation within the InN matrix, and show a characteristic diameter of ∼5 nm with average distance of ∼500 nm. These observations suggest the effective solubility of O in InN could be below 1 at. % at 500 °C. © 2005 American Institute of Physics.