Fig. 1. (Color online) (a) The process schematic diagram of the preparation of GaN nanorods. (b) The PL spectra of GaN before and after graphene transfer. (c) The Raman spectra of graphene grown on copper foil.

Fig. 2. The basic process of GaN nanorod formation by SEM at different etching time: (a) 3, (b) 5, (c) 10, (d) 15, (e) 17, and (f) 22 min.

Fig. 3. (Color online) (a) The cross-sectional structure of the graphene–GaN nanorod array heterojunction ultraviolet detector. (b) An optical microscope image of the device structure, and the inset is an SEM image of GaN nanorods. (c, d) The I–V characteristics of graphene–GaN nanorods photodetectors in darkness and light. (e, f) The variation of current with time at the bias of –5 V under the cyclic ultraviolet illumination of the detector.

Fig. 4. (Color online) (a) The band structure of the graphene–GaN nanorod array heterostructure. (b) A curve of device photoresponsivity as bias voltage changes. (c) The bias voltage and light power as a function of D*. (d) The spectral response curve of the detector at the bias of –5 V.

Table 1. The performance comparison of graphene (G) and Ga-based materials heterostructure photodetectors.