Lattice vibration of ZnSe1-xTex epilayers grown by molecular-beam epitaxy

The lattice vibration of ZnSe1-xTex epilayers grown using molecular-beam ep itaxy was investigated with Raman as well as Fourier transform infrared ref lectance spectroscopy. The dependence of longitudinal-optical (LO) and tran sverse-optical (TO) phonon frequency on the Te concentration was found to f ollow previous theoretical predictions. However, additional vibration modes were observed at the energy between that of the LO and TO phonons. The mic roscopic force constants F-ZnTe and F-znSc were evaluated to be 6.46 x 10(6 ) amu x (cm(-1))(2) and 2.91 x 10(6) amu x (cm(-1))(2,) respectively. In ad dition, the Raman spectra were recorded at high pressure up to 20 GPa. The pressure at which the semiconductor to metal transition occurred is charact erized by the disappearance of the LO phonon and found to decrease with the Te concentration. Current results imply the decreasing crystal stability w ith the Te concentration. [S0163-1829(99)01612-4].