Twin domain and antiphase boundaries in microcrystals of Κ-phase Ga2O3

The structural properties of twin domain boundaries (TDB) and antiphase boundaries (APB) in individual thin, hexagonal prismatic microcrystals of kappa-Ga2O3 grown on GaN/sapphire template with HVPE were investigated with electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The microcrystals were composed from the domains with three in-plane 120 degrees rotational orientations. It was found that every individual twin domain contains a parallel array of APBs of a high density stretched in the [010] direction. APBs possess steps or interruption and can form double oppositely shifted spatially separated layers (APB dipoles). TDBs on majority of their length are incoherent being not strictly flat and serve as the border for the APBs interruptions. Panchromatic cathodoluminescence mapping of the microcrystals revealed that not all TDBs and APBs reduced its intensity. The interruptions and steps of APBs were proposed to be the main origin of the excess charged carrier recombination. A model of the atomic structure in the vicinity of the defects is proposed and the assumption about the formation of local high strain regions and dangling bonds was made.