Several types of buffer layer structures, including superlattice and step-graded layers, have been employed to reduce the threading dislocation in SiGe epitaxial layers. A new technique, using a 0.1 μm thick Si buffer grown at 450°C by molecular beam epitaxy, provides the best results. For a 0.5 μm thick Si0.85Ge0.15 layer, the dislocation density is ≤ 105 cm-2. Hall measurements indicate an improvement in the hole mobility of a 1 μm thick Boron doped Si0.7Ge0.3 layer. A SiGe/Si heterojunction bipolar transistor has been fabricated exploiting the low temperature Si buffer. Transmission electron microscopy of the structure does not indicate any evidence of threading dislocations.
Bibliographical noteFunding Information:
The authors would like to thank Dr. J. Mansfield and Hal Estry for their assistance with TEM. The work is supported by the Air Force Office of Scientific Research under Grant F49620-95-1-0013 and by an AASERT Fellowship (AFOSR) under Grant F49620-94-0404.
- LT-Si buffer
- Threading dislocation density
ASJC Scopus subject areas
- Condensed Matter Physics
- Inorganic Chemistry
- Materials Chemistry