Enhanced Fabry-Perot resonance in GaAs nanowires through local field enhancement and surface passivation

We report substantial improvements in the photoluminescence (PL) efficiency and Fabry-Perot (FP) resonance of individual GaAs nanowires through surface passivation and local field enhancement, enabling FP peaks to be observed even at room temperature. For bare GaAs nanowires, strong FP resonance peaks can be observed at 4 K, but not at room temperature. However, depositing the nanowires on gold substrates leads to substantial enhancement in the PL intensity (5X) and 3.7X to infinite enhancement of FP peaks. Finite-difference time-domain (FDTD) simulations show that the gold substrate enhances the PL spectra predominately through enhanced absorption (11X) rather than enhanced emission (1.3X), predicting a total PL enhancement of 14X in the absence of non-radiative recombination. Despite the increased intensity of the FP peaks, lower Q factors are observed due to losses associated with the underlying gold substrate. As a means of reducing the non-radiative recombination in these nanowires, the surface states in the nanowires can be passivated by either an ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI)) or an AlGaAs surface layer to achieve up to 12X enhancement of the photoluminescence intensity and observation of FP peaks at room temperature without a gold substrate.