Raman scattering by epitaxial GaAs on a Si substrate

The strain distribution and the lattice disorder of GaAs on a Si substrate were studied by Raman scattering technique as a function of distance from the GaAs/Si interface. Epitaxial layers of GaAs grown by the laser-assisted metalorganic chemical vapor deposition technique on a Si substrate were subjected to slow chemical etching in successive steps, and Raman spectra were observed after each etch procedure. The asymmetry of the longitudinal optical (LO) phonon peak and the ratio of the integrated intensity of LO phonon to that of the transverse optical phonon Raman peaks increase for successive chemical etching, and the LO-phonon peak shifts to lower energies. Our Raman results indicate changes in lattice stacking, disorder, and strain in the epilayer as a function of distance from the GaAs/Si interface.