Bent-Shaped Twin Boundary in β-Ga₂O₃ Crystals

Twin boundary (TB) as a two-dimensional defect will constrain the size of the crystal material, reduce the yield of single crystals, and affect the performance of subsequent devices. For β-Ga2O3, it is one of the most promising ultrawide-band-gap semiconductor materials, which is severely limited by the twinning problem. In this paper, the unpenetrated twin structure with bent-shaped TB in the β-Ga2O3 bulk crystal was found and discussed in detail. The orientation difference and microstructure on the atomic scale of the bent-shaped TB in β-Ga2O3 have been intensively investigated from the (010) and (100) orientations using electron backscatter diffraction (EBSD) and spherical aberration-corrected scanning transmission electron microscopy (AC-STEM) imaging techniques. The results indicate that the bent-shaped TB is 180° TB, formed by the combination of incoherent TB (ITB) and (100)-coherent TB (CTB). The ITB can be further represented as a combination of (1̅02)-CTB and (100)-CTB. The formation mechanism of the bent-shaped TB in β-Ga2O3 is elucidated based on the TB formation energy (ETB) and crystal growth kinetics. This study reveals the microstructure and formation mechanism of bent-shaped TB and enriches the work on crystal defects in β-Ga2O3.