W0344

Universal Theory for the Determination of Both Screw and Edge Dislocation Densities for GaN and Related Materials using High Resolution X-ray Diffraction. Simon Bates, Bede Scientific Inc., 14 Inverness Dr. E., Suite H-100, Englewood, CO 80112 USA.

High resolution x-ray diffraction is a powerful tool for the measurement of dislocation density within bulk substrates and epi-layer materials. The broadening of the x-ray diffraction peak along specific directions can be directly related to specific types of dislocations once the instrumental function has been removed. However, until now there has not been a single theoretical approach for modeling all accessible reflections. A self consistent ‘mosaic block’ model of both screw and edge threading dislocations will be presented. The model predicts peak broadening along the omega axis for the symmetric as well as the in-plane asymmetric Bragg reflections driven by screw dislocations and finite correlation length effects. The change in the measured omega peak width as a function of the 2Theta and Omega offset angle allows the direct extraction of the screw dislocation density. Edge dislocations give broadening along the omega axis for out of plane asymmetric Bragg reflections only. By analyzing the change in the omega peak width as a function of the Chi offset allows the extraction of the edge dislocation density. The full model will be presented along with its application to a series of GaN samples with known electrical properties.