Defect imaging of SiGe strain relaxed buffers grown by LEPECVD

We compare four different selective etching solutions commonly used to highlight threading dislocations (TD), in SiGe hetero-epitaxial layers. The aim is to identify, amongst the many reported in the literature, an etching solution effective over the whole Ge concentration range. Etching experiments have been performed on Si1−xGex linearly graded relaxed buffer layers with a final germanium concentration x   varying from x=0.2x=0.2 to 0.9. All samples have been deposited on Si(1 0 0) by low-energy plasma-enhanced chemical vapour deposition (LEPECVD). The experimental results show that a variant of the so-called Schimmel-etch is successful in revealing TD over the Ge concentration range investigated.