PC-Mon-P6 - Investigation of dislocation types and line vectors of threading dislocations in aluminum nitride using monochromatic and white-beam X-ray topography
2. Physics and characterizationRoland Weingärtner1, Merve Kabukcuoglu2, Gleb Lukin1, Sven Besendörfer1
1 Fraunhofer Institute for Integrated Systems and Device Technology, Erlangen, Germany
2 Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology, Karlsruhe, Germany
Abstract text
Aluminum nitride (AlN) is a wide-bandgap semiconductor with potential applications in high-power electronics and optoelectronic devices. Wafer processing and device manufacturing require an ideally defect-free material and a large crystal diameter. Knowledge about the dislocation content is crucial for an improvement of the bulk crystal growth process regarding diameter enlargement as well as for the understanding of epitaxial layer quality and anomalous behavior of electronic devices. To date, there is no established technique that allows for obtaining such information on full wafer scale using laboratory equipment. A dislocation is characterized by its line vector and Burgers vector, which contain information about the orientation, type and strength of the dislocation. Due to the stress field around the dislocations, they appear as a local contrast in the measured topographic images depending on the diffraction conditions and can thus be visualized in spatial resolution.
In this work we investigate dislocation types and line vectors of threading dislocations (TDs) in AlN crystals and wafers, using monochromatic laboratory X-ray topography (XRT) and white-beam synchrotron XRT. The goal is to obtain reliable information about the full dislocation content in AlN samples to provide feedback for crystal growth. Comparison of the results obtained by monochromatic XRT with those performed by white-beam XRT allows us to develop an understanding of the capabilities and limitations of each setup. By using a geometric model for the interpretation of dislocations’ contrasts on the detector and utilizing visibility criteria we show a full characterization of dislocations’ line and Burgers vectors by combining measurements of different reflexes and orientations. By providing this analysis we can give a comprehensive overview about the different TDs that are present in a wafer. This information can be used to investigate the propagation of dislocations during multi-generation crystal growth and to correlate local electrical properties of epitaxial layers to different types of dislocations in the substrate. This represents an important step in the characterization of AlN and helps bringing the material closer to industrial applicability.