Atomic Force Microscopy Study of Self-Assembled Si1-xGex Islands Produced by Controlled Relaxation of Strained Films

Self-assembled Si1−xGex islands were studied in detail using atomic force microscopy. The self-assembled Si1−xGex islands were formed by a novel two-step process. First, highly strained Si1−xGex thin films (with x∼0.4) were selectively grown on a silicon wafer by chemical vapor deposition at 650 °C. The growth was followed by an annealing step performed in hydrogen at 750 °C at reduced pressure conditions for specific times. The size and distribution of the islands was found to be a function of the annealing conditions and an ordered pattern could be achieved with specific annealing conditions. This growth process shows a new way of creating device islands, which are confined within oxide regions and could be ordered, for applications in optical and electronic devices on silicon.