Line-shaped defects in bulk β-Ga2O3 single crystals grown by the vertical Bridgman method

We conducted an investigation of line-shaped defects, extending in the 〈010〉 direction, in bulk β-Ga2O3 single crystals grown by the vertical Bridgman (VB) method. Parallelepiped cross-section samples with {010} polished surfaces and {100} cleavage planes were prepared and were then etched in phosphoric acid at 140 °C. Rhombic etch pits were observed on the (010) surface and they were similar in shape to those reported as nanometer-sized grooves or plate-like nanopipes in crystals grown by the edge-defined film-fed growth (EFG) method. Groove-like voids in the 〈010〉 direction were also observed on {100} cleavage planes below the etch pits observed on the {010} surface. Therefore, we concluded that line-shaped defects observed in VB-grown crystals are similar to defects observed in EFG-grown crystals. The size of these defects was considerably smaller than that observed in EFG-grown crystals, but with a density of 5 × 105 cm−2. Based on these results, possible formation mechanisms for such defects were discussed.