Defects and their charge imaging on semiconductor surfaces by noncontact atomic force microscopy and spectroscopy

By using the noncontact atomic force microscope (AFM), at first, the optimal distance to image atomic point defects and periodic lattice structure was clarified on p-GaAs(1 1 0) cleaved surface. Next, Fe-doped semi-insulating InP(1 1 0) cleaved surface was observed, where various kinds of atomic point defects such as defects with different depths, and also mobile and immobile atomic defects were found. Finally, the atomic corrugation and the charge of atomic point defects on n(+)-GaAs(1 1 0)cleaved surface were imaged, simultaneously. It showed clearly that there are atomic point defects with and without point charge, and that the sign of point charge is positive. Further, the electron clouds which screen positive point charges on the surface and also below the surface were observed. (C) 2000 Elsevier Science B.V. All rights reserved.