Fig. 1. (Color online) The scheme of the lattice crystallographic basis in the β-Ga₂O₃ crystal sample. “A region” is the central region with a high level of crystal perfection; “B region” is the edge region with a lower crystal perfection.

Fig. 2. (Color online) XRD ω-scan curves for the β-Ga₂O₃ in the as-cut sample, (a) 8¯04 reflection of A region; (b) 6¯03 reflection of B region.

Fig. 3. (Color online) XRD θ−2θ curve pattern for the β-Ga₂O₃ sample in the as-cut state, the 2¯01 reflection, B region.

Fig. 4. SEM images of the surface of β-Ga₂O₃ samples (A region) that were subjected to etching at the following modes: (a) 10 min/250 °C/H₃PO₄ (EM2); (b) 5 min/200 °C/KOH (EM3). The crystallographic orientation depicted in (a) is applicable for (b). [4¯01¯]_p is a projection of [4¯01¯] direction on (2¯01) plane.

Fig. 5. (Color online) The etching pits distribution along the sample surface (B region): (a) optical image of the surface of the β-Ga₂O₃ sample subjected to EM2; (b) distribution of the etch pits at this surface.

Fig. 6. SEM images of the β-Ga₂O₃ sample surfaces (B region), subjected to: (a) as-cut sample; (b) AM1 + EM2; (c) AM2 + EM2; (d) AM3 + EM2; (e) AM4 + EM2; (f) AM3 + EM3; and (g) AM4 + EM3. The crystallographic orientation depicted in (a) is applicable for (b−g). [4¯01¯]_p is a projection of the [4¯01¯] direction.

Fig. 7. XRD ω-scan curve for the β-Ga₂O₃ sample upon the AM2 + EM2 procedure for the 2¯01 reflection: (a) A region; (b) B region.

Fig. 8. XRD data for the β-Ga₂O₃ sample upon AM4 + EM2: (a) θ−2θ curve pattern (6¯03 reflection); (b) ω-scan pattern (6¯03 reflection); both are registered in the B region.