The lattice vibration of (Formula presented) epilayers grown using molecular-beam epitaxy was investigated with Raman as well as Fourier transform infrared reflectance spectroscopy. The dependence of longitudinal-optical (LO) and transverse-optical (TO) phonon frequency on the Te concentration was found to follow previous theoretical predictions. However, additional vibration modes were observed at the energy between that of the LO and TO phonons. The microscopic force constants (Formula presented) and (Formula presented) were evaluated to be (Formula presented) and (Formula presented) respectively. In addition, the Raman spectra were recorded at high pressure up to 20 GPa. The pressure at which the semiconductor to metal transition occurred is characterized by the disappearance of the LO phonon and found to decrease with the Te concentration. Current results imply the decreasing crystal stability with the Te concentration.
|Number of pages||4|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|State||Published - 1 Jan 1999|