Optical Properties of the Alloy System SnTeGeTe from Reflectance Measurements

The reflectance spectra of bulk samples of the alloy series Sn1−xGexTe are measured at room temperature in the wavelength range 0.2 to 50 μm. The principal optical constants are obtained using Kramers‐Kronig analysis. The variations of the optical dielectric constant, the carrier effective mass, the optical mobility, and the optical energy gap are given as functions of the alloy fraction x. For the Sn‐rich alloys (x < 0.3) the energy gap and the dielectric constant do not follow the trends established for the series at the Ge‐rich side, and are possibly related to the cubic‐rhombohedral phase transition that occurs in this system. The mobility and effective mass, though, behave reasonably for all alloy fractions.