Imaging misorientation and strain of single dislocations in GaN using electron backscatter diffraction

Electron backscatter diffraction (EBSD) in the scanning electron microscope is a powerful technique for the structural characterisation of crystalline materials. Recent advances in hardware and software have significantly improved the spatial resolution and sensitivity of orientation and strain of EBSD, enabling the detection of small misorientations, strain distributions and extended defects in nominally single crystal thin films. In this work, we demonstrate that EBSD can now resolve individual dislocations, identify their type and quantify relative local rotations and deviatoric strain associated with threading dislocations (TDs) in a GaN semiconductor thin film. By acquiring multiple EBSD datasets, we imaged approximately 2000 TDs and determined an average TD density of 8 × 108 cm-2. About 40 % were identified as edge TDs, with the remainder being pure screw or mixed TDs. For our interaction depth of ≈20 nm, the misorientation at a TD was on the order of a few mrad and the strain variation was approximately 1 × 10–3 (or 1 mm/m). Interpretation of these measurements were supported by isotropic elasticity simulations of rotations and strain due to TDs accounting for both bulk (infinite medium) and surface relaxation effects. These results establish EBSD as a viable method for direct imaging and quantitative analysis of dislocations in semiconductor thin films.