RAMAN-SCATTERING IN INAS1-XSBX ALLOYS GROWN ON GAAS BY MOLECULAR-BEAM EPITAXY

Phonon energies in InAs1-xSbx ternary alloys, grown on GaAs by molecular beam epitaxy, have been studied by Raman scattering. The microstructure for this alloy system depends strongly on the growth temperature. For growth temperatures above 400-degrees-C, transmission electron microscopy (TEM) shows the alloy epilayer to be homogeneous. Raman spectra of these homogeneous InAsSb alloys show a strong InAs-like longitudinal optical (LO) phonon line, as well as an InSb-like LO line, throughout the composition range. The frequency of the InAs-like LO phonon varies linearly with composition. For growth temperatures below 400-degrees-C and compositions near the middle of the range, an interleaved platelet structure, arising from phase separation, is observed in TEM. Effects of phase separation in these alloys have been observed in the Raman spectra.