GROWTH MODE OF GE ON GAAS(100)

The surface morphology of single- and multilayer Ge films on GaAs(100) has been studied using low-energy electron diffraction and scanning t unneling microscopy (STM). After deposition of 0.5 monolayer, the Ge a toms form dimers with Ga atoms after annealing to 875 K, resulting in a (1X2) ordered surface layer. A Ge multilayer deposited at 700 K show s a mixture of (1X2) and (2x1) phases. When annealed at higher tempera tures, the (2X1) structure begins to disappear, and, eventually, only the (1X2) phase remains after annealing at 875 K. STM images of the su rface reveal faceted clusters of Ge that are surrounded by relatively smooth areas of (1X2) order. Based on these observations, we suggest t hat the Ge film grows on GaAs(100) by the Stranski-Krastanov mechanism at high temperatures. Because the lattice strain is negligible, the d riving force for this growth mode is a reduction in the total surface energy by minimizing substrate-induced electronic effects. Comparison of Ge growth on GaAs(100), GaAs(110), and Si(100) substrates shows the important role of surface and bulk electronic structure in determinin g the growth mode. The observed antiphase-domain-free GaAs growth on G e/GaAs(100) is explained based on our results.