IN-SITU SCANNING TUNNELING MICROSCOPE STUDIES OF HIGH-ENERGY, FOCUSEDION-IMPLANTATION OF GA INTO GAAS - DIRECT OBSERVATION OF ION-BEAM PROFILES

The profile of an ion beam line exposure of Ga+ ions into GaAs(100) wa s characterized in situ using scanning probe microscopy. Current imagi ng tunneling spectroscopy was used to characterize the surface defects induced by the high-energy Ga+ ions. Spatially reproducible features, approximately one per ion and 2-3 nm in diameter, were observed on th e irradiated surface. Differential conductance spectra of these featur es indicated that the image contrast was due to acceptor states induce d in the surface band gap. The density of these defects was used to fo rm a profile of the ion beam in the semiconductor surface. The resulti ng profile was in excellent agreement with the two-Gaussian fit report ed in previous work. (C) 1998 American Vacuum Society.