Fig. 1. (a) SEM morphology of the vertical GaN nanowire array; (b) HRTEM image of a single GaN nanowire; (c) XRD pattern of the vertical GaN nanowire array; (d) Raman spectrum of the monolayer graphene film.

Fig. 2. (a) Schematic diagram of the UV-IR dual-color detector based on GaN/graphene heterojunction; (b) optical microscopy image of the top of the fabricated device.

Fig. 3. Energy band and carrier transition diagrams of the graphene/GaN nanowire heterojunction under illumination.

Fig. 4. (a) I–V characteristic of the device measured at room temperature in the dark. The inset shows the H versus I used to estimate φB at the graphene/GaN heterojunction; (b) spectral response of the detector at a bias of −5V; (c) peak responsivities of the detector under different bias voltages at different wavelengths; (d) dark current and output photocurrent versus bias at 360 nm and 1540 nm.

Fig. 5. Schematic of the transient spectral response test system.

Fig. 6. (a) and (b) Multi-periodic and monocycle transient response of the device to 365 nm LED irradiation; (c) and (d) multi-periodic and monocycle transient response of the device to 1500 nm LED irradiation.