A comparative study of (100) GaAs films grown by liquid-phase epitaxy, molecular-beam epitaxy and metal-organic chemical vapor deposition by Raman spectroscopy

Abstract

We investigated (100) GaAs films grown by liquid-phase epitaxy, molecular-beam epitaxy and metal-organic chemical vapor deposition by Raman spectroscopy. The crystalline quality of the epitaxial films grown by the different techniques, as determined by the linewidth and intensity of the symmetry-allowed LO phonon lines, is found to be comparable. Symmetryforbidden TO phonon lines were observed in some undoped molecular-beam epitaxial films, and in heavily doped p-type (≥ 10¹⁸ cm⁻³) samples. The possible causes for its presence in each case are discussed. The Raman spectrum obtained from an interfacial region between GaAs and Al_0.35 Ga_0.65 As films showed an enhancement of the LO phonon-plasmon coupled mode and the TO mode presumably due to reduced carrier depletion near the interface and breakdown of selection rules due to disorder, respectively. It is suggested that Raman spectroscopy can be used as a technique to characterize interfaces in a multilayer structure.