THERMAL STRESS-INDUCED, HIGH-STRAIN FRAGMENTATION OF BURIED SIGE LAYERS GROWN ON SI

Buried Si1-xGex layers grown on Si at elevated temperatures of 700 to 800 degrees C generally exhibit x-ray rocking curves which are significantly broader than those predicted for perfect crystals, suggesting that the layers are strain-relieved. However, calculations using these rocking curves show the materials to be either nearly- or fully-strained. The source of x-ray broadening accompanied by high strain is found to be an abrupt, thermally-induced fragmentation of the layer into small, slightly misoriented regions during the cool-down, such that the as-grown strain remains unchanged. The fragments are typically rectangles a few micrometers wide, with well-defined boundaries along [110]-type directions.