Optical properties of InxGa1-xN alloy and In0.5Ga0.5N/GaN multi
quantum wells have been investigated in the region of far infrared. Far-IR
reflectivity spectra of In0.5Ga0.5N/GaN multi quantum wells on GaAs
substrate have been obtained by oblique incidence p- and s-polarization light
using effective medium approximation. The spectra and the dielectric
functions response give a good information about the phonon and plasmon
contribution in doped MQW as well as the mole fraction of compounds in
the alloys. The changes in position of optical modes are good tools for
measurement of the amount of free carrier and the amount of mole fraction
in the samples. During study of InxGa1-xN reflectivity spectra, two distinct
reststrahl bands with frequency near those of pure InN and GaN were
observed over entire composition range. Each band shifts to lower
frequencies and decreases in amplitude as the concentration of
corresponding compound in alloy decreased. Analysis of dielectric function
gives the TO-like and LO-like mode frequencies. The changes in LO mode
frequencies, due to coupling of phonon–plasmon, have been observed.