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

Abstract

A two-temperature process has been applied to grow 80-nm Si 0.7Ge 0.3 films on Si(001) by molecular-beam epitaxy (MBE). The first 30 nm were deposited at a reduced temperature of only 150–200°C (low-temperature stage). The subsequent growth was performed at 550°C, 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.