Fig. 1. (Color online) (a) Raman spectra and (b) the transmittance spectra of bare GaN.

Fig. 2. (Color online) (a) X-ray diffraction patterns of Ag−Au NPs/GaN heterojunction synthesized at the various temperatures and (b) a magnified image of plane (111) of the various sample (DV1 to DV4).

Fig. 3. (Color online) (a) Normalized Ag 3d XPS spectra, (b) Au 4f XPS spectra and (c) XPS survey for Ag AuNPs/GaN.

Fig. 4. (Color online) (a) The structure of Ag−Au NPs/GaN heterojunction-based UV photodetector, (b) and (c) photocurrent−voltage curves under illumination of 365 nm, and (d) the ON/OFF ratio of devices fabricated without and with Ag−Au alloys.

Fig. 5. (Color online) The current−time on the ON/OFF state of (a) bare GaN-based device and (b) DV3-Ag−Au NPs/GaN-based device. (c) Responsivity and (d) external quantum efficiency of Ag−Au NPs/GaN-based photodetector treated at 650 °C.

Fig. 6. (Color online) The energy level diagram and the transfer of chargers mechanism of a NPs/GaN-based photodetector.