Size distribution of Ge islands grown on Si(001)

Atomic force microscopy analyses were performed on Ge islands on Si(001) grown by low pressure chemical vapor deposition in the temperature range from 525 to 700 degrees C. A comparison with theoretical models describing the growth, of coherently strained and plastically relaxed islands is given to describe the observations. The mean diameter of coherently strained islands is found to be 170 nm over a wide range of temperature, whereas plastically relaxed islands grow up to diameters >500 nm. The aspect ratio turns out to be independent of the presence of dislocations. For the sample grown at 700 degrees C three size regimes could be observed, whereas the sample grown at the lowest temperature exhibits no island formation. At 550 degrees C islands with an average diameter of 33 nm and a low aspect ratio were observed; these could prove to be interesting in applications using quantum confinement effects. (C) 1997 American Institute of Physics.