Optical Properties of Zinc Telluride in the Infrared

ZnTe crystals were grown in a high pressure Tammann Furnace and doped with various kinds of impurities up to a carrier concentration of 8×10 18 cm -3 . The transmission and reflection spectra of undoped ZnTe crystals were measured in the region 100∼500 cm -1 . From the reflection spectrum the frequency values of TO (=179 cm -1 ) and LO (=206 cm -1 ) at the zone center and the effective charge of 0.62 e were determined. Absorption maxima in the transmission spectra could be assigned with the assumption that TO=175 cm -1 , LO=157 cm -1 , TA=73 cm -1 , and LA=126 cm -1 at the zone boundaries. The reliability of these values was checked by comparison with the data of other II-VI compounds and by the Brout sum rule. The reflection from heavily doped ZnTe crystals was interpretated in terms of the interaction of plasmons with optical phonons. The effective mass of the heavy holes was determined from this analysis to be (1.5±0.1) m 0 .