Atomic-Scale Characterization of Extended Defects in Wurtzite GaN Heterostructures

Abstract

We present an overview of the atomic structure of extended defects in wurtzite III-nitrides, focusing on GaN heterostructures applicable to light-emitting optoelectronic devices (LEDs and lasers) and radio frequency (RF) power electronics. We provide experimental routines to visualize and recognize these defects with aberration-corrected scanning transmission electron microscopy (STEM). Line, planar, and volume defects are imaged, with examples taken from InGaN multi quantum well heterostructures, epitaxially grown on Si. We demonstrate how the different line and planar defects can be identified by visualizing either the extra or sheared planes that are characteristic to each defect or by differentiating their unique atomic column projections through depth-sectioning. Volume defects in the form of locally phase-separated InN and metallic indium precipitates were also identified via spatially resolved electron energy-loss spectroscopy. The classification of defects established in this work and the methods to visualize them will be a reference to researchers in this field and will provide a foundation for the targeted engineering of future III-nitrides.