Line shape and profile of the LO phonon modes in mixed alloy system $In_{1-x-y}Ga_xAl_yAs$ epitaxial layers grown on InP

Abstract

In this work, linewidth variations versus compositions of the first-order longitudinal optic (LO) phonon modes in the mixed alloy system are studied. The asymmetry and broadening of the LO modes is explained using a "spatial correlation" model with a Gaussian correlation function. The system investigated here were $In_{1-x-y}Ga_xAl_yAs$ quaternary alloys lattice-matched to InP(with x+y $\apprx$ 47%). The quaternary alloy samples were grown as epilayers on (00l)InP substrates by molecular beam epitaxy(MBE).