Bulk plasmon-phonon polaritons in n-GaN

E Yu Orlov,S Suihkonen,V A Shalygin,G A Melentev

doi:10.1088/1742-6596/816/1/012004

Abstract

We studied theoretically and experimentally plasmon-phonon polaritons and longitudinal plasmon-phonon oscillations in n-GaN epitaxial layers. The studies were carried out on the epitaxial layers with various doping levels. Simulation of the reflectivity spectra and dispersion relations of plasmon-phonon polaritons was performed in a wide frequency range. Reflectivity spectra transformation associated with phonon damping and electron relaxation processes has been revealed. Experimental studies of the reflectivity spectra have been performed in the spectral range of 8–80 meV. The experimental spectra are well fitted by the simulated ones. Results of the study can be used for contactless determination of the electron concentration and mobility in GaN epitaxal layers.

Highlights

During recent years, bulk and surface polaritons are extensively researched in order to create midinfrared and terahertz selective sources [1,2,3]
We present theoretical consideration taking into account the optical phonon damping and electron relaxation processes
To summarize, we studied theoretically and experimentally the bulk plasmon-phonon polaritons in n-GaN with various doping levels

Summary

Introduction

Bulk and surface polaritons are extensively researched in order to create midinfrared and terahertz selective sources [1,2,3]. This behavior indicates that the contribution of the electromagnetic field energy to the plasmon polariton energy is dominant, and the contribution of the mechanical energy of transverse electron oscillations is negligible As it is known, the linear dispersion dependence ω describes the propagation of a “pure” photon in a medium with the dielectric permittivity ε ∞. Longitudinal electromagnetic waves can propagate at these two frequencies These oscillations are known as the coupled plasmon-phonon modes, they have no dispersion (see two blue lines in figure 1 (c)). Specific transverse electromagnetic waves (plasmon-phonon polaritons) can be excited in a doped polar semiconductor These waves represent coupled transverse oscillations of the electromagnetic field, lattice and electron gas which cannot be separated. Longitudinal plasmon-phonon modes in n-GaN To take into account the optical phonon damping and electron relaxation processes, instead of equation (6) we used a more general expression for the dielectric permittivity of a polar semiconductor [4, 5]:

TO iωγ

Conclusion