STEP-EDGE ENERGETICS OF THE GE GAAS(001)-(1X2) SUPERSTRUCTURE/

For the first time the step-edge energies have been measured for a sup erstructure resulting from nonpolar/polar heteroepitaxy. Using scannin g tunneling microscopy, we have investigated the morphology of the Ge/ GaAs(001)-(1 x 2) reconstructed surface using substrates miscut by 1 d egrees and 2 degrees toward the [110] direction to expose the A-type s teps. The superstructure has well-defined step edges and smooth terrac es, even when the initial substrate is rough. The primary defect struc tures are antiphase domain boundaries remaining from the formation of the (1 x 2) reconstruction. The kink energies are similar to these for the A-type steps on both the GaAs(001)-(2 x 4) and Si(100)-(2 x 1) su rfaces. In addition, there is an apparent kink-kink attraction of abou t 120 meV between nearest-neighbor kinks. Using the model incorporatin g nearest-neighbor interactions between kinks developed for the Ge/GaA s(001)(1 x 2) superstructure, the kink-kink repulsion observed on GaAs (001)-(2 x 4) is discussed quantitatively and shown to involve energie s significantly higher than those which could be reasonably attributed to dipole-dipole interactions. (C) 1998 Elsevier Science B.V.