Two types of etching pits in (100) β-Ga2O3 single crystals grown by casting method

Two types of micron-sized etching pits were observed on (100) plane of β-Ga2O3 single crystals grown by casting method. Type A etching pits were elongated along [010] direction with a density of 105/cm2. Using FIB and HRTEM, the atomic structure under the pits bottom remained complete but exhibited continuous microscopic strain, which could be attributed to strain-related. On the other hand, type B etching pits represented different geometric parameters, with 2 times larger and 6 times deeper than type A. Edge dislocations with clearly dislocation lines which perpendicular to b = <100> were observed. The origins of etching pits were clarified, especially the co-exist strain-related pits. After annealing at 1200 °C for 3 h in air, we found varying degrees of reduction in the density of both etching pits, which could be owing to partial stress release and dislocations slip at the oxygen-containing ambient during elevated temperature.