Radiation damage and surface modification of GaAs(001) by MeV C+ and C-2(+) co-implantation with Ga2+

Radiation damage and Surface modifications of semi-insulating GaAs(0 0 1) s ubstrates upon 1 MeV C+ and 2 MeV C-2(+) coimplantation with Ga2+ have been studied by X-ray reflectometry, combined Rutherford backscattering/channel ing and transmission electron microscopy. Two disordered layers - one near- surface and another deeper - are formed. Additionally the electron density of the near-surface region has been found to be lower compared to bulk GaAs . This has been attributed to vacancy-enrichment in this region. The disord er caused by C-2 implantation is higher compared to C. Assuming that the ne ar-surface disorder is partially caused by electronic excitation in the sem i-insulating substrate, a possible reason for this difference is the cohere nt dynamic response of the electrons in the target due to vicinage of C ato ms in the C-2 cluster. In the deeper layer, overlap of damage cascades migh t be responsible for the higher damage caused in the cluster implantation. (C) 1999 Elsevier Science B.V. All rights reserved.