STUDY OF PLASMON-LO-PHONON COUPLING IN TE-DOPED GA1-XALXAS

Plasmon-LO-phonon coupling in n-type Ga1-xAlxAs has been investigated by measuring the infrared reflectivity spectra of differently doped n-type samples having x0.14, x0.30, and x0.46. Two expressions for the dielectric function, one an additive form and the other a factorized form, have given satisfactory fits to the reflectivity data. The mode frequencies and damping rates in the plasmon-LO-phonon coupled mode systems are calculated and compared with the observed ones for the samples having x0.14 and x0.46. The -point conduction-band effective mass for x0.14 is found to be m*=(0.13±0.01)me and the resistivity obtained from the infrared spectra is approximately 30% higher than the value from dc measurements. The reflectivity minima are broadened by the large plasma damping in the samples having x0.46. © 1979 The American Physical Society.