Observation of dislocations in β-Ga_2O_3 single-crystal substrates by synchrotron X-ray topography, chemical etching, and transmission electron microscopy

摘要

To reveal dislocations in beta-Ga2O3 and categorize them by their Burgers vectors, we have carried out a comprehensive dislocation characterization by synchrotron X-ray topography (XRT), chemical etching, and transmission electron microscopy (TEM). An important type of dislocation confirmed by XRT is the screw-type dislocations extending in the & x3008;010 & x3009; direction at a density of about 4.2 x 10(4) cm(-2). These dislocations had length in millimeters and seldom bent to other directions. Chemical etching using molten KOH + NaOH at 200 degrees C formed hillocks with multiple crystallographic facets on the (010) surface. These hillocks showed various geometrical features that indicated the direction of the dislocation lines. TEM observation confirmed that the hillocks were related to dislocations. Finally, the feasibility of using TEM weak-beam dark-field images and large-angle convergent-beam electron diffraction to identify dislocation Burgers vectors was examined, which seemed to be problematic due to the low-symmetry of the monoclinic crystal structure of beta-Ga2O3.