Direct evidence of LO phonon-plasmon coupled modes in n-GaN

摘要

We report theoretical results of the far-infrared transmission in oblique incidence for undoped and doped GaN epilayers. For c-GaN, our results in p-polarization find transmission minima at LO and TO frequencies while in s-polarization only one minima corresponding to TO mode is revealed. For c-GaN/GaAs/AlN (buffer) layer we noticed minima in s-polarization corresponding to TO modes of c-GaN and c-AlN while in p-polarization the features related to TO modes as well as minima linked to LO modes are found. The shift in L_+ modes with increasing carrier concentration (N) provided direct evidence of estimating N in doped GaN.