IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Semiconductors Tuesday Sessions
       Session SC-TuA

Paper SC-TuA6
The Strain Relaxation Mechanism of SiGe Growth with a Low Temperature Si Buffer Layer by Molecular-beam Epitaxy

Tuesday, October 30, 2001, 3:40 pm, Room 124

Session: Semiconductor Heterojunctions
Presenter: S.W. Lee, National Tsing Hua University, Taiwan, R.O.C.
Authors: S.W. Lee, National Tsing Hua University, Taiwan, R.O.C.
Y.H. Peng, National Taiwan University, Taiwan, R.O.C.
H.C. Chen, National Tsing Hua University, Taiwan, R.O.C.
H.H. Cheng, National Taiwan University, Taiwan, R.O.C.
C.H. Kuan, National Taiwan University, Taiwan, R.O.C.
L.J. Chen, National Tsing Hua University, Taiwan, R.O.C.
Correspondent: Click to Email
Recently, the use of the low temperature Si (LT-Si) buffer layer to achieve dislocation-free SiGe films was found to be effective to share the mismatch strain in epilayers. However, the mechanism of strain relaxation in a LT-Si buffer layer has not been well understood. In the present work, the growth of 300-nm-thick Si@sub0.7@Ge@sub0.3@ films with a LT-Si buffer layer grown at 550°C~350°C and with thickness of 50nm~250nm have been carried out by molecular-beam epitaxy. The SiGe films were characterized by transmission electron microscopy (TEM), double-axis x-ray diffraction (DAXRD), atomic force microscopy (AFM) and photoluminescence (PL). From DAXRD measurement, Si@sub0.7@Ge@sub0.3@ films with a 100-nm-thick LT-Si buffer layer grown at different temperatures were found to be fully relaxed (100%). However, Si@sub0.7@Ge@sub0.3@ films became partially relaxed with increased thickness of LT-Si buffer layers. From cross-section TEM (XTEM) observation, the microstructures of LT-Si buffer layers change with deposition temperature and thickness of LT-Si layers. XTEM images showed that the distribution of dislocations formed in the LT-Si buffer layer is correlated with the degree of relaxation. The strain relaxation mechanism is explained in terms of the compliant effect of LT-Si buffer. A novel method based on this mechanism using a thin Ge layer interposed below the LT-Si buffer layer for Si@sub0.7@Ge@sub0.3@ growth is demonstrated. The interposed Ge layer plays a critical role in leading the misfit dislocations to transverse along the LT-Si/Si interface. Controlling misfit dislocations in LT-Si buffers was achieved. The interposed Ge layer was expected to promote the relaxation of the top SiGe films.