MORPHOLOGY OF THE IMPLANTATION-INDUCED DISORDER IN GAAS STUDIED BY RAMAN-SPECTROSCOPY AND ION CHANNELING

Disorder was introduced into GaAs by implantation of Si-30(+) ions, us ing a very wide range of ion doses, dose rates, and implant temperatur es, and studied by Raman scattering (RS) and Rutherford backscattering ion channeling (RBS). RS spectra were deconvoluted consistently and s ystematically into up to four components, one of them being an apparen t background signal interpreted here as a boson peak. Arguments are gi ven that this signal represents the second amorphous phase different f rom a continuous random network. An intercascade distance model (ICD) was postulated, which estimates the average distance, L-ICD, between i mplantation-induced cascades as a function of ion dose. An analogous p arameter, L-RBS, was calculated from the RBS damage fraction f(RBS). F rom RS data the correlation length L-RS, representing the size of crys talline regions with preserved translational symmetry, was determined by fitting the LO signal within the spatial correlation model. All thr ee L's agree nicely, proving the equivalency of the correlation length and intercascade distance. This enabled a straightforward comparison of relevant signals and a direct correlation between RS and RBS. While measure of damage in RES (f(RBS)) reflects the disordered volume frac tion of the implanted layer, RS measures simultaneously the lowering o f the translational symmetry (an effect that prevails at lower doses) and the fraction of disordered volume (prevailing at higher doses). A considerable difference in sensitivity between RS and RBS to particula r defects enabled the differentiation of six different types of implan tation-introduced disorder.