Raman scattering studies of reactive ion-etched MBE

The use of Raman scattering to characterize the effects of reactive ion etching (RIE) on the surface properties of single-crystal molecular beam epitaxy (MBE)-grown 〈100〉 n-type GaAs is discussed. The longitudinal optic (LO) phonon and the coupled plasmon LO-phonon modes observed in the Raman spectra were studied for highly Si-doped samples with the free carrier concentrations between 5×10¹⁸ and 9×10¹⁸ cm^-3 to probe the surface quality. Symmetry forbidden transverse optic phonon Raman spectra provided information about the surface quality of lightly Si-doped samples with free carrier concentrations of 3×10¹⁷ cm^-3. Electrical measurements on Schottky diodes formed on lightly doped RIE samples support the results of the Raman studies. The effect of rapid thermal annealing was also studied by Raman scattering. Samples etched at ion energies of 400 eV showed surface disorder confined to within 10±2 nm from the surface. It is shown that using a low-pressure multipolar reactive ion etch system at ion bombardment energies <;200 eV allows etching without introducing measurable surface disordering.