Bulk plasmon-phonon polaritons in n-GaN

Interaction of surface plasmon–phonon polaritons with terahertz radiation in heavily doped GaAs epilayers

“…For s-polarized radiation apart from the above reflectivity decrease, the grating sample demonstrates the same peculiarities as the planar sample, namely, a sharp dip at the photon energies close to ω − and the reflectivity edge at ω ≈ ω +. Both of the features are related to the bulk PPhPs in n-GaAs epilayer, similar to the case of profiled and planar n-GaN epilayers reported by us earlier [11,14].…”

“…Both the ranges are rather narrow and separated by a wide band where surface waves cannot propagate (see figure 1(b)). On the contrary, in the case of a heavily doped polar semiconductor when ω P ≈ ω LO or even ω P > ω LO (see figure 1(c)), ω − is close to ω TO and ω + > ω LO [11], which signifies that the plasma reflection band overlaps with the Reststrahlen band. Therefore the surface PPs interact with surface PhPs, causing formation of composite waves called as surface plasmonphonon polaritons (PPhPs).…”

“…For a doped semiconductor (ω P = 0), the equation ε (ω) = 0 has two roots (we denote them as ω − and ω +) corresponding to longitudinal bulk electromagnetic waves which represent coupled plasmon-phonon modes and propagate at these two frequencies [9,10]. In the case of a lowly doped semiconductor (when 0 < ω P ω TO ), ω − ≈ ω P (ω TO /ω LO ) ω TO and ω + ≈ ω LO [11], which means that there are two spectral ranges where the dielectric permittivity is negative and R ω = 1 (see figure 1(b)). One of these ranges (ω TO < ω < ω + ) practically coincides with the Reststrahlen band considered above (figure 1(a)) i.e.…”