Defect distribution and morphology development of SiGe layers grown on Si(100) substrates by LPE

摘要

Thick relaxed SiGe layers having Ge content up to 13 at.precent have been grown using a liquid phase epitaxy (LPE) technique. The thickness of the layers is around 20-30 #mu#m. The strain relaxation and the resulting defect evolution during the growth of SiGe layers are found to be largely controlled by the growth kinetics involved in the LPE growth process. The cooling rate of the LPE process plays an important role in the supersaturation of solute materials in the growth process. A greater number of ridges and trenches are formed on the layer on using high cooling rates. The effect of cooling rate on the morphology development of the layers is significant for the layers having low Ge content. The wavelength of undulation of the SiGe layers decreases from 75 to 20 #mu#m as the cooling rate during the LPE process is increased from 20 to 500 K/h. The etch pit density of the layers also increases from 2X10~4 to 8X10~5 cm~(-2) as the cooling rate is increased. Pyramidal growth results upon increasing the Ge content in the layer above 13 at.precent.