SURFACE DAMAGE AND DEPOSITION ON GALLIUM-ARSENIDE RESULTING FROM LOW-ENERGY CARBON ION-BOMBARDMENT

A mass-separated carbon ion beam in the energy range of 20-500 eV was used in ultrahigh vacuum to study the ion-surface interactions that occur in alkane based reactive ion etching of GaAs. The effects of ion bombardment and of subsequent damage-removal treatments were determined by measuring the surface chemistry and band-bending changes with in situ polar-angle-dependent X-ray photoelectron spectroscopy. The study showed that carbon ion bombardment on GaAs even at 20 eV resulted in carbon incorporation and the formation of carbide species. Initially, slight sputtering occurred with a higher sputter yield for arsenic than that for gallium, but further ion exposure led to the formation of an amorphous carbon overlayer. The degree of arsenic depletion and the thickness of the damaged and carbon-contaminated layer increased with the impact energy. The carbon and carbide residues were not removed by annealing at 520-degrees-C. or by exposure to ultraviolet light/ozone. Bombardment with 100 eV hydrogen ions did remove the damage induced by carbon ion bombardment.