Room-Temperature Hole Plasmons and Plasmon-Phonon Interactions in Epitaxial <i>p</i>-Type Scandium Nitride.

Das, Prasanna; Mukhopadhyay, Debmalya; Bartelsen, Emma R; Karanje, Renuka; Maurya, Krishna Chand; Rao, Pavithra; Kamalasanan Pillai, Ashalatha Indiradevi; Selvaraja, Shankar Kumar et al. · Nano Lett · 2026

basic_science · Level V

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Abstract

The plasmon resonance represents collective oscillations of free electrons, enabling subwavelength light confinement and local field enhancement in conductive media. While electron-based plasmons in metals and <i>n</i>-type semiconductors have been widely explored, their hole-based counterparts in <i>p</i>-type semiconductors remain largely underexplored due to low hole densities and large effective masses that push plasmon response to the far-infrared with strong damping. Here, we present conclusive experimental evidence of low-loss, room-temperature hole plasmons in the mid-infrared regime, realized in epitaxial <i>p</i>-type scandium nitride thin films. Enabled by a high hole concentration of ∼1.4 × 10<sup>20</sup> cm<sup>-3</sup> and mobility of ∼21 cm<sup>2</sup> V<sup>-1</sup> s<sup>-1</sup>, these hole plasmons exhibit strong confinement with moderate damping. Furthermore, by tuning hole concentrations to spectrally overlap the plasmonic resonance with surface phonon polaritons, we demonstrate a mixed hole-plasmon-LO-phonon interaction giving rise to broadband hybrid absorption response. These results establish robust hole plasmonics in <i>p</i>-type semiconductors for infrared nanophotonic devices.