Fig. 1. Synthesis of Bi/Ga₂O₃ heterojunction PDs.

Fig. 2. (a) XRD pattern of Bi film at 100°C. (b) Raman spectra of Bi thin films with different thicknesses (3, 10, and 30 nm). (c)–(e) AFM images of Bi thin films with different thicknesses (3, 10, and 30 nm). (f) Output characteristics of 10 nm thick Bi film with a gate bias voltage of 0 V.

Fig. 3. (a) Side view schematic of the (111)-oriented 2D Bi/Ga₂O₃ heterojunction. (b) XRD patterns of Ga₂O₃ film and Bi/Ga₂O₃ film.

Fig. 4. (a) XPS spectra of β-Ga₂O₃/Bi. (b)–(d) Fitted Bi 4f, Ga 3d, and O 1s XPS spectra of β-Ga₂O₃. (e) Valence band maximum (VBM) energy level spectrum of Ga₂O₃.

Fig. 5. (a) Typical I -V curves of the Bi/Ga₂O₃ heterojunction optoelectronic device under 254 nm illumination with various light intensities. (b) Responsivity and specific detectivity of the Bi/Ga₂O₃ PD as a function of incident light intensity. (c) EQEs and PDCRs of the device at various light intensities. (d) Time dependence of the current with different bias voltages at a light intensity of 10 µW/cm².

Fig. 6. (a) Energy band diagram of Bi and Ga₂O₃ before contact. (b) Energy band diagram of the device in forward bias under UV illumination.