Reactive Ion Etching of MBE GaAs: A Raman Scattering Study

The effect of reactive ion etching (RIE) on Si-doped molecular beam epitaxial (MBE) grown GaAs has been studied by Raman scattering. The MBE samples were grown on doped substrates having a free carrier concentration of 1.5 x 1018 cm-3 . The ID phonon and coupled plasmon-ID phonon modes of reactive ion etched (RIE) GaAs were studied to determine both depletion widths and carrier concentrations. Measurable surface disorder, confined to within 10 nm of the surface, is observed for ion bombardment energies of > 300 eV. The Raman spectra of highly doped samples (N = 8 x 1018 cm-3 ), along with the I-V measurements of Schottky barriers made with RIE samples of lower free carrier concentration (N = 3 x 1017 cm-3 ), indicate that samples reactively ion etched with energies <200 eV provide a high quality GaAs surface.