Fig. 1. (Color online) Unit cell of β-Ga₂O₃, which possesses two nonequivalent Ga sites: Ga (I), Ga (II), and three nonequivalent O-sites. Projection of the unit cell of β-Ga₂O₃ along the c- (A), a- (B) and b-axes (C). The figure was adopted from Ref. [9].

Fig. 2. (Color online) Electronic band structure of β-Ga₂O₃^[15].

Fig. 3. (Color online) (a) Sketch of an early furnace used by Verneuil. (b) Simplified diagram of Verneuil process for synthesizing Ga₂O₃^[16].

Fig. 4. (Color online) Schematic of float zone single crystal growth.

Fig. 5. (Color online) As-grown crystals along the crystallographic axis (a- <100>), (b- <010>), (c- <001>]).

Fig. 6. Schematic of Czochralski method.

Fig. 7. (Color online) Semiconducting β-Ga₂O₃ crystals of 2 cm (a, c) and 5 cm (b, d) diameter grown at low- (a, b) and high-oxygen concentrations (c, d)^[25].

Fig. 8. (Color online) Edge-defined film-fed growth method.

Fig. 9. (Color online) (a) Photograph of EFG-grown β-Ga₂O₃ bulk crystal. (b) Photographs of processed β-Ga₂O₃ substrates. (c) 2-inch wafer by Electronic Material Research Institute of Tianjin. (d) 2-inch plate by Shanghai Institute of Optics and Fine Mechanics.

Fig. 10. (Color online) Bridgman technique.

Fig. 11. (Color online) β-Ga₂O₃ crystals were grown using the VB method in ambient air. (a–a’) Crystal was grown in a full-diameter crucible, and (b–b’) crystal was grown in a conical crucible. The figure was adopted from Ref. [38].

Fig. 12. (Color online) Schematics of line-shaped defects. The figure was adopted from Ref. [40].

Fig. 13. The comparison of the melt growth methods for β-Ga₂O₃ bulk single crystals.

Fig. 14. (Color online) Theoretical ideal performance limits of β-Ga₂O₃ power devices in comparison with those of other major semiconductors. The figure was adopted from Ref. [58].

Fig. 15. (Color online) Schematic illustration: (a) cross-section and (b) optical micrograph of Ga₂O₃ MESFET. According to the description from Ref. [62].