Interplay of dislocation network and island arrangement in SiGe films grown on Si(001)

A two-temperature process has been applied to grow 80-nm Si0.7Ge0.3 films on Si(001) by molecular-beam epitaxy (MBE). The first 30 nm were deposited at a reduced temperature of only 150-200 degreesC (low-temperature stage). The subsequent growth was performed at 550 degreesC, the temperature range conventionally applied for SiGe MBE. Using atomic-force microscopy, we observed that the misfit dislocation network introduced during sample heating after the low-temperature (LT) stage guides the arrangement of {105}-faceted pyramid-like islands. In the case of a very narrow dislocation network - induced by ion-assisted growth during the LT stage - a checkerboard array of {105}-faceted pits and pyramids evolves with a 'lattice constant' of approximately 200 nm. (C) 2000 Elsevier Science B.V. All rights reserved.