Raman Study of Misfit Strain and Its Relaxation in ZnSe Layers Grown on GaAs Substrates

Abstract

Raman spectra are measured on ZnSe epitaxial layers with a thickness of 0.09∼3.4 µm grown on GaAs(100) substrates by low-pressure vapor phase epitaxy both in RF hydrogen plasma and in plasma-free conditions. A 1 cm^-1 high-frequency shift is observed in the longitudinal optical (LO) Raman peak for layers thinner than 0.2 µm grown in the plasma-free condition. The shift is due to the two-dimensional elastic strain in epitaxial layers. No frequency shift is observed for layers grown in hydrogen plasma, even for the thinnest layer. The LO phonon scattering efficiency depends on the distance from layer-substrate interface.