Thermal stability of the strained-Si/Si0.7Ge0.3 heterostructure

Thermal stability of the strained-Si/Si0.7Ge0.3 heterostructure was investigated by secondary-ion mass spectroscopy, Raman spectroscopy, and atomic force microscopy. Ge atoms diffused out through the strained-Si layer during heat treatment of 1000 °C for 1 h. The activation energy of Ge diffusion in strained Si was 3.3 eV, which was lower than the value in unstrained Si (4.7–5.3 eV). Strain in the strained-Si layer did not change after thermal treatment at 950 °C or less for 1 h. Slip lines due to strain relaxation formed at the surface of the strained-Si layer for the samples treated at 950–1000 °C for 1 h. For practical application of the strained-Si/Si0.7Ge0.3 heterostructure to electron devices, the maximum thermal budget should be made less than that equivalent to 900 °C annealing for 1 h.