SUBMONOLAYER SI DEPOSITION AT LOW-TEMPERATURES ON THE GAAS(001)-(2X4)SURFACE STUDIED BY SCANNING-TUNNELING-MICROSCOPY

Si deposition at low substrate temperatures (240 and 360 degrees C) on the GaAs(001)-(2 x 4) surface has been studied by scanning tunneling microscopy (STM) and reflection high-energy electron diffraction (RHEE D). The Si was deposited in the absence of a direct As-4 flux up to a coverage of 0.8 monolayer (ML). The STM images reveal that the prefere ntial Si incorporation site lies in the trenches between the As dimer row-a of the (2 x 4) reconstruction. Here, it substitutes the missing Ga and is subsequently covered with As from the residual As-4 backgrou nd to result in fully As-terminated areas. Above 0.4 ML, Si dimer rows form on top of this As. The RHEED patterns continuously change with i ncreasing Si coverage from the initial (2 x 4) to an asymmetric (3 x 1 ) pattern. Annealing at 450 degrees C results in a (2 x 4) reconstruct ed surface with disorder and kinks in the As dimer rows. (C) 1998 Else vier Science B.V. All rights reserved.