OBSERVATION OF POINT-DEFECTS AND MICROFACETING ON GAAS(110) SURFACES BY SCANNING TUNNELING MICROSCOPY

The cleaved (110) surface of n-doped GaAs has been investigated by STM with atomic resolution under uhv conditions. Depending on the cleavage direction and the quality of the cleavage terraces, different forms were found with mainly monoatomic steps running in different directions. Point defects occurring as a depression along the [110] direction with the lateral dimensions of one atomic site were observed for both atomic species. In contrast to the As point defects, the Ga point defects were found to be negatively charged since their apparent size in the constant current mode depends on the tunneling voltage. Both point defects can be interpreted as Ga or As vacancies. © 1990 Pergamon Press plc.