Single-crystalline Aluminum Nanostructures on Semiconducting GaAs Substrate for Ultraviolet to Near-infrared Plasmonics

TL;DR

This paper demonstrates the fabrication and optical characterization of single-crystalline aluminum nanostructures on GaAs substrates, revealing their plasmonic properties from UV to NIR and insights into their nonlinear photoluminescence behavior.

Contribution

It introduces a method to create high-quality aluminum nanostructures on GaAs for plasmonics, with detailed analysis of their optical resonances and nonlinear responses.

Findings

Aluminum nanostructures support UV to NIR plasmonic resonances.

TPPL efficiency depends on excitation polarization and substrate properties.

High-quality, ultrasmooth aluminum films improve plasmonic performance.

Abstract

Aluminum, as a metallic material for plasmonics, is of great interest because it extends the applications of surface plasmon resonance into the ultraviolet (UV) region and excels noble metals in the natural abundance, cost and compatibility with modern semiconductor fabrication process. Here, we present UV to near-infrared (NIR) plasmonic resonance of single-crystalline aluminum nanoslits and nanoholes. The high-definition nanostructures are fabricated with focused ion-beam (FIB) milling into an ultrasmooth single-crystalline aluminum film grown on a semiconducting GaAs substrate with molecular beam epitaxy (MBE) method. The single-crystalline aluminum film shows improved reflectivity and reduced two-photon photoluminescence (TPPL) due to the ultrasmooth surface. Both linear scattering and non-linear TPPL are studied in detail. The nanoslit arrays show clear Fano-like resonance and the nanoholes are found to support both photonic modes and localized surface plasmonic resonance. We also found that TPPL generation is more efficient when the excitation polarization is parallel rather than perpendicular to the edge of the aluminum film. Such counter-intuitive phenomenon is attributed to the high refractive index of the GaAs substrate. We show that the polarization of TPPL from aluminum well preserves the excitation polarization and is independent of the crystal orientation of the film or substrate. Our study gains insight into the optical property of aluminum nanostructures on high-index semiconducting GaAs substrate and illustrates a practical route to implement plasmonic devices onto semiconductors for future hybrid nanodevices.