Relaxation mechanism of low temperature SiGe/Si(001) buffer layers

摘要

A detailed analysis is presented on relaxation mechanism of low temperature Si_(1-x)Ge_x layers deposited on Si(001) by low pressure chemical vapor deposition. While Si_(1-x)Ge_x layers with x = 0.02-0.20 deposited above 680℃ relax by formation of 60°dislocations characterized by fast propagation, at lower growth temperature the relaxation mechanism changes. The critical thickness is reduced markedly, relaxation is fast being governed by dislocations with slow propagation. This indicates the presence of a high density of point defects in the low temperature layers. We used these features to realize relaxed buffer layers with a low density of threading dislocations.