Dislocation Charge Density Quantification Using Precessed STEM Differential Phase Contrast

GaN threading dislocations accumulate charge with density and sign varying according to their dislocation type and the dominant charge carrier. Leakage current due to these dislocations has a deleterious effect on the performance of GaN electronic devices. Previ-ous transmission electron microscopy studies have used electron holography to determine electric potential profiles across individual dislocations and the implied charge density. The electron holography experiment, however, requires careful setup and specialized equipment to produce useful results. We demonstrate measurement of local electric field and charge density of GaN threading dislocations using (precessed) 4D-STEM differential phase con-trast (DPC). Electric field associated with the dislocations deflects electrons as they pass through the lamella, causing a corresponding shift in the center of mass of the direct beam. Precessed scanning smooths the dynamical diffraction due to strain associated with the dislocations, improving signal:noise in the DPC signal. 4D-STEM additionally allows near-simultaneous dislocation Burgers vector identification by virtual dark field imaging. This approach can be applied broadly to other material systems such as oxides where dislocation charge is responsible for the speed of ionic diffusion.