Discovery of Polar Semiconducting Scandium Nitride as an Infrared Plasmon and Phonon-Polaritonic Material

Interaction of light with collective charge oscillations termed as plasmon-polariton and with polar lattice vibrations termed phonon-polariton is a new frontier in nano-photonics. Traditionally doped-semiconductors and conducting metal oxides (CMO) are used to achieve plasmon-polaritons in the near-to-mid infrared (IR), while polar dielectrics are utilized for realizing phonon-polaritons in the long-wavelength IR (LWIR) spectral regions. However, demonstrating plasmon- and phonon-polariton in one host material with low-loss is challenging due to the mutually conflicting physical property requirements. In this article, we demonstrate high-quality tunable short-wavelength IR (SWIR) plasmon-polariton and LWIR phonon-polariton in complementary metal-oxide-semiconductor (CMOS) compatible group III-V polar semiconducting scandium nitride (ScN) thin films. We achieve both resonances by utilizing n-type (oxygen) and p-type (magnesium) doping in ScN that allows modulation of carrier concentration from 5 × 1018 to 1.6 × 1021 cm-3. Our work enables infrared nano-photonics with an epitaxial group-III semiconducting nitride, opening the possibility for practical applications.