IDENTIFICATION OF DISLOCATIONS IN N-TYPE SI SI0.88GE0.12/SI HETEROSTRUCTURES BY DEEP-LEVEL TRANSIENT SPECTROSCOPY/

Plastic relaxation of Si1-xGex layers on (100) Si leads to formation o f misfit dislocations at the heterointerface and threading dislocation s through the heterostructure. We report here a deep-level transient s pectroscopy (DLTS) investigation of dislocations in n-type Si/Si0.88Ge 0.12/Si heterostructures grown by selective epitaxy using low-pressure chemical vapour deposition (LPCVD). DLTS was used to detect deep stat es correlated with dislocations. Measurements were performed on large- area samples (relaxation degree of 63%) as well as on small areas (rel axation degree of 4%) grown selectively on the same wafer. The bias-de pendent DLTS peak heights are consistent with a spatially varying disl ocation density. This variation, and the combined interpretation of th e corresponding DLTS peaks from large and small areas, allowed us to a ssociate one of the deep levels with misfit dislocations at the hetero interface, a second one with threading dislocations and the third one with defects present in the SiGe layer near the interface.