Role of surface instability and anisotropy in strain relaxation of epitaxial SiGe on Si(110)

We report on the morphological evolution of strained, low-mismatch Si0.67Ge 0.33 and Si0.75Ge0.25 films on Si (110), covering both the elastic and earl y stages of plastic relaxation during growth. It is seen that three-dimensi onal island formation is suppressed at 650 and 700 degrees C on the Si (110 ) surface, unlike on the Si (100) surface under the same growth conditions. Instead, a high density of ledges oriented along an elastically hard [111] direction, and a very low density of nanowires oriented along the single i n-plane [110] azimuth are observed. Continued growth leads to the formation of misfit defects oriented along the [110] direction and disappearance of the nanowires. (C) 1999 American Institute of Physics. [S0021-8979(99)01811 -3].