Author:
Lu Jinggang,Rozgonyi George,Seacrist Mike
Abstract
In this paper, defects and strain in SiGe heterostructures with 8, 13, 25, or 40 nm strained-Si (sSi) on top of 300 or 600 nm Si0.77Ge0.23 buffer have been examined. We found that threading dislocations (TDs) in the super-critical thickness sSi samples are more evenly distributed, while they are severely trapped inside TD pileups in the sub-critical thickness sSi samples. Raman spectroscopy revealed that the relaxation degree of the 300 nm SiGe layer decreases from 80% to 67% with the sSi layer increase from 8 nm to 40 nm. This suggests a continuous relaxation of the highly compressively strained, thin SiGe buffer during or even after sSi growth, and its gradual suppression by presence of a tensile strained sSi layer. Based on these observation, we suggest that an in-situ thermal annealing prior to the sSi growth will help to enhance the strain relaxation of thin SiGe buffers.
Publisher
The Electrochemical Society