Damping effect of longitudinal optical phonon—plasmon coupling on thermal radiation from surface micro-gratings on direct and indirect electronic transition type semiconductors

Abstract

Thermal radiation properties of surface micro-Au-line and space structures on direct and indirect electronic transition-type semiconductors of n-type (n-) GaAs and GaP, respectively, are studied. The electron densities range from 0.62 to 1.0 × 1018 cm−3. The emission spectra of samples on n-GaAs wafers show peak energies significantly shifted from the longitudinal optical (LO) phonon energy due to the LO-phonon−plasmon coupling (LOPC) at 630 K, while partial decoupling is observed. The thermal emission from the sample on n-GaP is peaked at 395.9 cm−1, shifted only by 1.5 cm−1 from the LO-phonon energy, with a linewidth of 12.5 cm−1 at 630 K. The effect of LOPC on the emission from the sample on n-GaP is mostly suppressed because of the electron localization in the X-valley, suggesting an advantage of indirect transition-type semiconductors in LO-phonon resonant infrared emitters using the phonons generated via the electron energy relaxation.