Fig. 1. Crystal structures of amorphous, mixed, and crystalline Ga₂O₃^[36]

Fig. 2. (a) Schematic diagram and photograph of the gallium-oxide MSM photodetectors; (b) TEM images of the gallium oxide films deposited by RFMS and MBE; (c) I-V characteristics and (d) transient response of the MSM photodetectors based on a-Ga₂O₃ and β-Ga₂O₃ thin films^[30]

Fig. 3. (a) I-V curves in dark and (b) under UV 254 nm light illumination; (c) Temporal response tests of the PDs with KrF pulse laser illumination at 10 V bias^[32]

Fig. 4. (a) I−V characteristics and (b) I-T characteristics of the devices fabricated at various growth temperatures^[58]; (c) Responsive characteristics and (d) I-T characteristics of the devices fabricated at various growth temperatures^[59]

Fig. 5. (a) Film roughness fitting results from XRR and AFM; (b) Top: fitting curve of film density from SE and XRR. Medium: the variation trend of the a-GaO_x bandgap. Bottom: Variation trend of Ga/O ratio based on XPS analysis^[60]

Fig. 6. (a) The I-V characteristics of the detectors based on a-GaO_x film and Mg: GaO_x film under dark and 255 nm illumination conditions; (b) Time-dependent photocurrent of devices based on different amorphous films^[42]

Fig. 7. (a) Schematic illustration of the flexible photodetector; (b) SEM image of the Ag NWs electrode; (c) Variations in photocurrent of the device^[68]

Fig. 8. (a) Schematic of the a-Ga₂O₃/ITO prototype device; (b) I−V characteristics of the devices fabricated at various growth temperatures in dark; (c) Schematic of band alignment of the Ga₂O₃/ITO heterojunction; (d) The I–T characteristic of the detector^[70]

Fig. 9. (a) Schematic diagram of the a-Ga2O3/p-Si heterojunctions photodetector, the enlarged view shows a cross-sectional view of the device; (b) The I–T characteristic of the detector without oxygen plasma treatment; (c) The I–T characteristic of the detector with oxygen plasma treatment^[71]

Fig. 10. (a) Schematic diagram of the fabrication steps of 3D urchin-like VO-Ga₂O₃/ZnO; (b) The I–T characteristic of the detector^[72]

Fig. 11. (a) Schematic structure of the GR/a-Ga₂O₃ flexible PD; (b) Schematics of the band diagram and the carrier transport mechanism of the GR/a-Ga₂O₃ under light irradiation^[73]

Fig. 12. (a) Cross-section image of the as-fabricated GaO_x phototransistor; (b) I_DS-V_G transfer characteristics measured at different V_DS in the dark and under 254 nm light illumination^[74]

Fig. 13. (a) I_DS-V_GS curves and I_GS-V_GS curves of the a-Ga₂O₃ TFTs with and without channel patterned; (b) Suppression of the PPC with a positive gate pulse^[75]

Fig. 14. (a) The photomask with letters “CAS” and (b) the image obtained from the imaging system^[74]; (c) Schematic diagram of the optical imaging system and (d) the obtained "C" pattern ^[82]; (e) Schematic diagram of the PDs array and (f) the obtained "E" pattern ^[83]

Fig. 15. (a) Schematic of the 3D Ga₂O₃ photodetector array, photograph and microscope image of an individual photodetector cell; (b) I-T curves of the photodetector at 15 V without bending and after 500 and 2000 bending cycles^[80]