PSEUDOMORPHIC GROWTH OF Ge//xSi//1// minus //x ON SILICON BY MOLECULAR BEAM EPITAXY.

Ge//xSi//1// minus //x layers are grown on Si substrates over the full range of alloy compositions at temperatures from 400-750 degree C by means of molecular beam epitaxy. At a given growth temperature films grow in a smooth, two-dimensional manner up to a critical germanium fraction x//c. Beyond x//c growth is rough. x//c increases from 0. 1 at 750 degree C to 1. 0 at approximately 550 degree C. Rutherford ion backscattering measurements indicate good crystallinity over a wide range of growth conditions. Transmission electron microscopy reveals that in thin films, the lattice mismatch between the Ge//xSi//1// minus //x and Si layers can be accommodated by lattice distortion rather than by misfit dislocation formation. This pseudomorphic growth condition can persist to alloy thicknesses as large as 1/4 mu m.