Defect density in non-selective and selective Si/SiGe structures

The epitaxial quality of Si (non-selective or selective epitaxy)/SiGe (non-selective or selective epitaxy) structures applying Si2H2Cl2 or SiH4 as the Si source has been studied. High-resolution reciprocal lattice mapping and X-ray reflectivity measurements have been used to characterise the epitaxial quality and the interfacial defects, respectively. The surface morphology of the structures was studied by atomic force microscopy. It is shown that the generation of defects in non-selective SiGe layers is strongly dependent oil the thickness of the buffer layer. Moreover, the selective growth of a Si buffer layer requires a growth temperature above 770degreesC in order to obtain a smooth layer surface, which is beneficial for the succeeding growth of the SiGe layer. The surface can also be smoothed by an annealing treatment at 900degreesC for 40 s. This annealing step is crucial to remove the interfacial defects in the case of Si/SiGe structures grown with different Si sources. (C) 2002 Elsevier Science B.V. All rights reserved.