Study on surface-enhanced Raman scattering performance of pitted GaN covered by Au layer

Rough surface with micro-nano pits can form large numbers of hot spots after noble metal deposition, which would be beneficial to improve surface enhanced Raman scattering (SERS) signal. In this study, we proposed a SERS substrate that GaN was etched by KOH and then covered by Au layer. Scanning electronic microscopy confirmed the thicknesses of Au layers and revealed many typical hexagonal micro-nano pits distributing on the surface. SERS results indicate the pitted GaN covered by the Au layer of 25 nm has best SERS intensity in our case, providing a good enhancement factor of 6. 57$\times 10^{7}$ and a limit of detection of approximately 1$0^{-9}$M for rhodamine 6G(R6G) used as a test molecule because of the electromagnetic mechanism at the interface between Au layers and R6G. A series of experiments demonstrate $\mathrm{A}\mathrm{u}/$pitted $\mathrm{G}\mathrm{a}\mathrm{N}$ with high sensitivity is potential for biomedical application.