Controlling the Electron Concentration for Surface-Enhanced Raman Spectroscopy

Controlling the intensity of surface-enhanced Raman spectroscopy (SERS) in a systematic manner is the key to understanding, and even predicting, the dynamics of the imposing phenomenon. It has been known that the SERS signal is intensified by resonant electron oscillation at the hot spots. To date, few of the reported SERS techniques are capable of confining the contributive charges with a controlled concentration and position. Here, we systematically increase the carrier population a few nanometers below the hot spots, aiming to quantify the dependence of SERS intensity on surface charge concentration. The work is accomplished by InGaN quantum wells (QWs) grown by metal-organic chemical vapor deposition (MOCVD). Characterizing the QW wafers with capacitance-voltage curves and the correspondent Raman spectra, we observe a linear logarithmic dependence of SERS intensity on the electron concentration. The intensity is further boosted by nanostructuring the QW surface with adjusted MOCVD conditions.